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llvm-for-llvmta/lib/Target/AArch64/AArch64FrameLowering.cpp

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//===- AArch64FrameLowering.cpp - AArch64 Frame Lowering -------*- C++ -*-====//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the AArch64 implementation of TargetFrameLowering class.
//
// On AArch64, stack frames are structured as follows:
//
// The stack grows downward.
//
// All of the individual frame areas on the frame below are optional, i.e. it's
// possible to create a function so that the particular area isn't present
// in the frame.
//
// At function entry, the "frame" looks as follows:
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------| <- sp
// | | Lower address
//
//
// After the prologue has run, the frame has the following general structure.
// Note that this doesn't depict the case where a red-zone is used. Also,
// technically the last frame area (VLAs) doesn't get created until in the
// main function body, after the prologue is run. However, it's depicted here
// for completeness.
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------|
// | |
// | (Win64 only) varargs from reg |
// | |
// |-----------------------------------|
// | |
// | callee-saved gpr registers | <--.
// | | | On Darwin platforms these
// |- - - - - - - - - - - - - - - - - -| | callee saves are swapped,
// | | | (frame record first)
// | prev_fp, prev_lr | <--'
// | (a.k.a. "frame record") |
// |-----------------------------------| <- fp(=x29)
// | |
// | callee-saved fp/simd/SVE regs |
// | |
// |-----------------------------------|
// | |
// | SVE stack objects |
// | |
// |-----------------------------------|
// |.empty.space.to.make.part.below....|
// |.aligned.in.case.it.needs.more.than| (size of this area is unknown at
// |.the.standard.16-byte.alignment....| compile time; if present)
// |-----------------------------------|
// | |
// | local variables of fixed size |
// | including spill slots |
// |-----------------------------------| <- bp(not defined by ABI,
// |.variable-sized.local.variables....| LLVM chooses X19)
// |.(VLAs)............................| (size of this area is unknown at
// |...................................| compile time)
// |-----------------------------------| <- sp
// | | Lower address
//
//
// To access the data in a frame, at-compile time, a constant offset must be
// computable from one of the pointers (fp, bp, sp) to access it. The size
// of the areas with a dotted background cannot be computed at compile-time
// if they are present, making it required to have all three of fp, bp and
// sp to be set up to be able to access all contents in the frame areas,
// assuming all of the frame areas are non-empty.
//
// For most functions, some of the frame areas are empty. For those functions,
// it may not be necessary to set up fp or bp:
// * A base pointer is definitely needed when there are both VLAs and local
// variables with more-than-default alignment requirements.
// * A frame pointer is definitely needed when there are local variables with
// more-than-default alignment requirements.
//
// For Darwin platforms the frame-record (fp, lr) is stored at the top of the
// callee-saved area, since the unwind encoding does not allow for encoding
// this dynamically and existing tools depend on this layout. For other
// platforms, the frame-record is stored at the bottom of the (gpr) callee-saved
// area to allow SVE stack objects (allocated directly below the callee-saves,
// if available) to be accessed directly from the framepointer.
// The SVE spill/fill instructions have VL-scaled addressing modes such
// as:
// ldr z8, [fp, #-7 mul vl]
// For SVE the size of the vector length (VL) is not known at compile-time, so
// '#-7 mul vl' is an offset that can only be evaluated at runtime. With this
// layout, we don't need to add an unscaled offset to the framepointer before
// accessing the SVE object in the frame.
//
// In some cases when a base pointer is not strictly needed, it is generated
// anyway when offsets from the frame pointer to access local variables become
// so large that the offset can't be encoded in the immediate fields of loads
// or stores.
//
// FIXME: also explain the redzone concept.
// FIXME: also explain the concept of reserved call frames.
//
//===----------------------------------------------------------------------===//
#include "AArch64FrameLowering.h"
#include "AArch64InstrInfo.h"
#include "AArch64MachineFunctionInfo.h"
#include "AArch64RegisterInfo.h"
#include "AArch64Subtarget.h"
#include "AArch64TargetMachine.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "frame-info"
static cl::opt<bool> EnableRedZone("aarch64-redzone",
cl::desc("enable use of redzone on AArch64"),
cl::init(false), cl::Hidden);
static cl::opt<bool>
ReverseCSRRestoreSeq("reverse-csr-restore-seq",
cl::desc("reverse the CSR restore sequence"),
cl::init(false), cl::Hidden);
static cl::opt<bool> StackTaggingMergeSetTag(
"stack-tagging-merge-settag",
cl::desc("merge settag instruction in function epilog"), cl::init(true),
cl::Hidden);
static cl::opt<bool> OrderFrameObjects("aarch64-order-frame-objects",
cl::desc("sort stack allocations"),
cl::init(true), cl::Hidden);
STATISTIC(NumRedZoneFunctions, "Number of functions using red zone");
/// Returns the argument pop size.
static uint64_t getArgumentPopSize(MachineFunction &MF,
MachineBasicBlock &MBB) {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
bool IsTailCallReturn = false;
if (MBB.end() != MBBI) {
unsigned RetOpcode = MBBI->getOpcode();
IsTailCallReturn = RetOpcode == AArch64::TCRETURNdi ||
RetOpcode == AArch64::TCRETURNri ||
RetOpcode == AArch64::TCRETURNriBTI;
}
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
uint64_t ArgumentPopSize = 0;
if (IsTailCallReturn) {
MachineOperand &StackAdjust = MBBI->getOperand(1);
// For a tail-call in a callee-pops-arguments environment, some or all of
// the stack may actually be in use for the call's arguments, this is
// calculated during LowerCall and consumed here...
ArgumentPopSize = StackAdjust.getImm();
} else {
// ... otherwise the amount to pop is *all* of the argument space,
// conveniently stored in the MachineFunctionInfo by
// LowerFormalArguments. This will, of course, be zero for the C calling
// convention.
ArgumentPopSize = AFI->getArgumentStackToRestore();
}
return ArgumentPopSize;
}
/// This is the biggest offset to the stack pointer we can encode in aarch64
/// instructions (without using a separate calculation and a temp register).
/// Note that the exception here are vector stores/loads which cannot encode any
/// displacements (see estimateRSStackSizeLimit(), isAArch64FrameOffsetLegal()).
static const unsigned DefaultSafeSPDisplacement = 255;
/// Look at each instruction that references stack frames and return the stack
/// size limit beyond which some of these instructions will require a scratch
/// register during their expansion later.
static unsigned estimateRSStackSizeLimit(MachineFunction &MF) {
// FIXME: For now, just conservatively guestimate based on unscaled indexing
// range. We'll end up allocating an unnecessary spill slot a lot, but
// realistically that's not a big deal at this stage of the game.
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
if (MI.isDebugInstr() || MI.isPseudo() ||
MI.getOpcode() == AArch64::ADDXri ||
MI.getOpcode() == AArch64::ADDSXri)
continue;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isFI())
continue;
StackOffset Offset;
if (isAArch64FrameOffsetLegal(MI, Offset, nullptr, nullptr, nullptr) ==
AArch64FrameOffsetCannotUpdate)
return 0;
}
}
}
return DefaultSafeSPDisplacement;
}
TargetStackID::Value
AArch64FrameLowering::getStackIDForScalableVectors() const {
return TargetStackID::ScalableVector;
}
/// Returns the size of the fixed object area (allocated next to sp on entry)
/// On Win64 this may include a var args area and an UnwindHelp object for EH.
static unsigned getFixedObjectSize(const MachineFunction &MF,
const AArch64FunctionInfo *AFI, bool IsWin64,
bool IsFunclet) {
if (!IsWin64 || IsFunclet) {
// Only Win64 uses fixed objects, and then only for the function (not
// funclets)
return 0;
} else {
// Var args are stored here in the primary function.
const unsigned VarArgsArea = AFI->getVarArgsGPRSize();
// To support EH funclets we allocate an UnwindHelp object
const unsigned UnwindHelpObject = (MF.hasEHFunclets() ? 8 : 0);
return alignTo(VarArgsArea + UnwindHelpObject, 16);
}
}
/// Returns the size of the entire SVE stackframe (calleesaves + spills).
static StackOffset getSVEStackSize(const MachineFunction &MF) {
const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
return StackOffset::getScalable((int64_t)AFI->getStackSizeSVE());
}
bool AArch64FrameLowering::canUseRedZone(const MachineFunction &MF) const {
if (!EnableRedZone)
return false;
// Don't use the red zone if the function explicitly asks us not to.
// This is typically used for kernel code.
if (MF.getFunction().hasFnAttribute(Attribute::NoRedZone))
return false;
const MachineFrameInfo &MFI = MF.getFrameInfo();
const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
uint64_t NumBytes = AFI->getLocalStackSize();
return !(MFI.hasCalls() || hasFP(MF) || NumBytes > 128 ||
getSVEStackSize(MF));
}
/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register.
bool AArch64FrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
// Win64 EH requires a frame pointer if funclets are present, as the locals
// are accessed off the frame pointer in both the parent function and the
// funclets.
if (MF.hasEHFunclets())
return true;
// Retain behavior of always omitting the FP for leaf functions when possible.
if (MF.getTarget().Options.DisableFramePointerElim(MF))
return true;
if (MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken() ||
MFI.hasStackMap() || MFI.hasPatchPoint() ||
RegInfo->needsStackRealignment(MF))
return true;
// With large callframes around we may need to use FP to access the scavenging
// emergency spillslot.
//
// Unfortunately some calls to hasFP() like machine verifier ->
// getReservedReg() -> hasFP in the middle of global isel are too early
// to know the max call frame size. Hopefully conservatively returning "true"
// in those cases is fine.
// DefaultSafeSPDisplacement is fine as we only emergency spill GP regs.
if (!MFI.isMaxCallFrameSizeComputed() ||
MFI.getMaxCallFrameSize() > DefaultSafeSPDisplacement)
return true;
return false;
}
/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
/// not required, we reserve argument space for call sites in the function
/// immediately on entry to the current function. This eliminates the need for
/// add/sub sp brackets around call sites. Returns true if the call frame is
/// included as part of the stack frame.
bool
AArch64FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
return !MF.getFrameInfo().hasVarSizedObjects();
}
MachineBasicBlock::iterator AArch64FrameLowering::eliminateCallFramePseudoInstr(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const AArch64InstrInfo *TII =
static_cast<const AArch64InstrInfo *>(MF.getSubtarget().getInstrInfo());
DebugLoc DL = I->getDebugLoc();
unsigned Opc = I->getOpcode();
bool IsDestroy = Opc == TII->getCallFrameDestroyOpcode();
uint64_t CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0;
if (!hasReservedCallFrame(MF)) {
int64_t Amount = I->getOperand(0).getImm();
Amount = alignTo(Amount, getStackAlign());
if (!IsDestroy)
Amount = -Amount;
// N.b. if CalleePopAmount is valid but zero (i.e. callee would pop, but it
// doesn't have to pop anything), then the first operand will be zero too so
// this adjustment is a no-op.
if (CalleePopAmount == 0) {
// FIXME: in-function stack adjustment for calls is limited to 24-bits
// because there's no guaranteed temporary register available.
//
// ADD/SUB (immediate) has only LSL #0 and LSL #12 available.
// 1) For offset <= 12-bit, we use LSL #0
// 2) For 12-bit <= offset <= 24-bit, we use two instructions. One uses
// LSL #0, and the other uses LSL #12.
//
// Most call frames will be allocated at the start of a function so
// this is OK, but it is a limitation that needs dealing with.
assert(Amount > -0xffffff && Amount < 0xffffff && "call frame too large");
emitFrameOffset(MBB, I, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(Amount), TII);
}
} else if (CalleePopAmount != 0) {
// If the calling convention demands that the callee pops arguments from the
// stack, we want to add it back if we have a reserved call frame.
assert(CalleePopAmount < 0xffffff && "call frame too large");
emitFrameOffset(MBB, I, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(-(int64_t)CalleePopAmount), TII);
}
return MBB.erase(I);
}
// Convenience function to create a DWARF expression for
// Expr + NumBytes + NumVGScaledBytes * AArch64::VG
static void appendVGScaledOffsetExpr(SmallVectorImpl<char> &Expr,
int NumBytes, int NumVGScaledBytes, unsigned VG,
llvm::raw_string_ostream &Comment) {
uint8_t buffer[16];
if (NumBytes) {
Expr.push_back(dwarf::DW_OP_consts);
Expr.append(buffer, buffer + encodeSLEB128(NumBytes, buffer));
Expr.push_back((uint8_t)dwarf::DW_OP_plus);
Comment << (NumBytes < 0 ? " - " : " + ") << std::abs(NumBytes);
}
if (NumVGScaledBytes) {
Expr.push_back((uint8_t)dwarf::DW_OP_consts);
Expr.append(buffer, buffer + encodeSLEB128(NumVGScaledBytes, buffer));
Expr.push_back((uint8_t)dwarf::DW_OP_bregx);
Expr.append(buffer, buffer + encodeULEB128(VG, buffer));
Expr.push_back(0);
Expr.push_back((uint8_t)dwarf::DW_OP_mul);
Expr.push_back((uint8_t)dwarf::DW_OP_plus);
Comment << (NumVGScaledBytes < 0 ? " - " : " + ")
<< std::abs(NumVGScaledBytes) << " * VG";
}
}
// Creates an MCCFIInstruction:
// { DW_CFA_def_cfa_expression, ULEB128 (sizeof expr), expr }
MCCFIInstruction AArch64FrameLowering::createDefCFAExpressionFromSP(
const TargetRegisterInfo &TRI, const StackOffset &OffsetFromSP) const {
int64_t NumBytes, NumVGScaledBytes;
AArch64InstrInfo::decomposeStackOffsetForDwarfOffsets(OffsetFromSP, NumBytes,
NumVGScaledBytes);
std::string CommentBuffer = "sp";
llvm::raw_string_ostream Comment(CommentBuffer);
// Build up the expression (SP + NumBytes + NumVGScaledBytes * AArch64::VG)
SmallString<64> Expr;
Expr.push_back((uint8_t)(dwarf::DW_OP_breg0 + /*SP*/ 31));
Expr.push_back(0);
appendVGScaledOffsetExpr(Expr, NumBytes, NumVGScaledBytes,
TRI.getDwarfRegNum(AArch64::VG, true), Comment);
// Wrap this into DW_CFA_def_cfa.
SmallString<64> DefCfaExpr;
DefCfaExpr.push_back(dwarf::DW_CFA_def_cfa_expression);
uint8_t buffer[16];
DefCfaExpr.append(buffer,
buffer + encodeULEB128(Expr.size(), buffer));
DefCfaExpr.append(Expr.str());
return MCCFIInstruction::createEscape(nullptr, DefCfaExpr.str(),
Comment.str());
}
MCCFIInstruction AArch64FrameLowering::createCfaOffset(
const TargetRegisterInfo &TRI, unsigned Reg,
const StackOffset &OffsetFromDefCFA) const {
int64_t NumBytes, NumVGScaledBytes;
AArch64InstrInfo::decomposeStackOffsetForDwarfOffsets(
OffsetFromDefCFA, NumBytes, NumVGScaledBytes);
unsigned DwarfReg = TRI.getDwarfRegNum(Reg, true);
// Non-scalable offsets can use DW_CFA_offset directly.
if (!NumVGScaledBytes)
return MCCFIInstruction::createOffset(nullptr, DwarfReg, NumBytes);
std::string CommentBuffer;
llvm::raw_string_ostream Comment(CommentBuffer);
Comment << printReg(Reg, &TRI) << " @ cfa";
// Build up expression (NumBytes + NumVGScaledBytes * AArch64::VG)
SmallString<64> OffsetExpr;
appendVGScaledOffsetExpr(OffsetExpr, NumBytes, NumVGScaledBytes,
TRI.getDwarfRegNum(AArch64::VG, true), Comment);
// Wrap this into DW_CFA_expression
SmallString<64> CfaExpr;
CfaExpr.push_back(dwarf::DW_CFA_expression);
uint8_t buffer[16];
CfaExpr.append(buffer, buffer + encodeULEB128(DwarfReg, buffer));
CfaExpr.append(buffer, buffer + encodeULEB128(OffsetExpr.size(), buffer));
CfaExpr.append(OffsetExpr.str());
return MCCFIInstruction::createEscape(nullptr, CfaExpr.str(), Comment.str());
}
void AArch64FrameLowering::emitCalleeSavedFrameMoves(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI) const {
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo &MFI = MF.getFrameInfo();
const TargetSubtargetInfo &STI = MF.getSubtarget();
const TargetRegisterInfo *TRI = STI.getRegisterInfo();
const TargetInstrInfo *TII = STI.getInstrInfo();
DebugLoc DL = MBB.findDebugLoc(MBBI);
// Add callee saved registers to move list.
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
if (CSI.empty())
return;
for (const auto &Info : CSI) {
unsigned Reg = Info.getReg();
// Not all unwinders may know about SVE registers, so assume the lowest
// common demoninator.
unsigned NewReg;
if (static_cast<const AArch64RegisterInfo *>(TRI)->regNeedsCFI(Reg, NewReg))
Reg = NewReg;
else
continue;
StackOffset Offset;
if (MFI.getStackID(Info.getFrameIdx()) == TargetStackID::ScalableVector) {
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
Offset =
StackOffset::getScalable(MFI.getObjectOffset(Info.getFrameIdx())) -
StackOffset::getFixed(AFI->getCalleeSavedStackSize(MFI));
} else {
Offset = StackOffset::getFixed(MFI.getObjectOffset(Info.getFrameIdx()) -
getOffsetOfLocalArea());
}
unsigned CFIIndex = MF.addFrameInst(createCfaOffset(*TRI, Reg, Offset));
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
}
// Find a scratch register that we can use at the start of the prologue to
// re-align the stack pointer. We avoid using callee-save registers since they
// may appear to be free when this is called from canUseAsPrologue (during
// shrink wrapping), but then no longer be free when this is called from
// emitPrologue.
//
// FIXME: This is a bit conservative, since in the above case we could use one
// of the callee-save registers as a scratch temp to re-align the stack pointer,
// but we would then have to make sure that we were in fact saving at least one
// callee-save register in the prologue, which is additional complexity that
// doesn't seem worth the benefit.
static unsigned findScratchNonCalleeSaveRegister(MachineBasicBlock *MBB) {
MachineFunction *MF = MBB->getParent();
// If MBB is an entry block, use X9 as the scratch register
if (&MF->front() == MBB)
return AArch64::X9;
const AArch64Subtarget &Subtarget = MF->getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo &TRI = *Subtarget.getRegisterInfo();
LivePhysRegs LiveRegs(TRI);
LiveRegs.addLiveIns(*MBB);
// Mark callee saved registers as used so we will not choose them.
const MCPhysReg *CSRegs = MF->getRegInfo().getCalleeSavedRegs();
for (unsigned i = 0; CSRegs[i]; ++i)
LiveRegs.addReg(CSRegs[i]);
// Prefer X9 since it was historically used for the prologue scratch reg.
const MachineRegisterInfo &MRI = MF->getRegInfo();
if (LiveRegs.available(MRI, AArch64::X9))
return AArch64::X9;
for (unsigned Reg : AArch64::GPR64RegClass) {
if (LiveRegs.available(MRI, Reg))
return Reg;
}
return AArch64::NoRegister;
}
bool AArch64FrameLowering::canUseAsPrologue(
const MachineBasicBlock &MBB) const {
const MachineFunction *MF = MBB.getParent();
MachineBasicBlock *TmpMBB = const_cast<MachineBasicBlock *>(&MBB);
const AArch64Subtarget &Subtarget = MF->getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
// Don't need a scratch register if we're not going to re-align the stack.
if (!RegInfo->needsStackRealignment(*MF))
return true;
// Otherwise, we can use any block as long as it has a scratch register
// available.
return findScratchNonCalleeSaveRegister(TmpMBB) != AArch64::NoRegister;
}
static bool windowsRequiresStackProbe(MachineFunction &MF,
uint64_t StackSizeInBytes) {
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
if (!Subtarget.isTargetWindows())
return false;
const Function &F = MF.getFunction();
// TODO: When implementing stack protectors, take that into account
// for the probe threshold.
unsigned StackProbeSize = 4096;
if (F.hasFnAttribute("stack-probe-size"))
F.getFnAttribute("stack-probe-size")
.getValueAsString()
.getAsInteger(0, StackProbeSize);
return (StackSizeInBytes >= StackProbeSize) &&
!F.hasFnAttribute("no-stack-arg-probe");
}
static bool needsWinCFI(const MachineFunction &MF) {
const Function &F = MF.getFunction();
return MF.getTarget().getMCAsmInfo()->usesWindowsCFI() &&
F.needsUnwindTableEntry();
}
bool AArch64FrameLowering::shouldCombineCSRLocalStackBump(
MachineFunction &MF, uint64_t StackBumpBytes) const {
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
const MachineFrameInfo &MFI = MF.getFrameInfo();
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
if (AFI->getLocalStackSize() == 0)
return false;
// For WinCFI, if optimizing for size, prefer to not combine the stack bump
// (to force a stp with predecrement) to match the packed unwind format,
// provided that there actually are any callee saved registers to merge the
// decrement with.
// This is potentially marginally slower, but allows using the packed
// unwind format for functions that both have a local area and callee saved
// registers. Using the packed unwind format notably reduces the size of
// the unwind info.
if (needsWinCFI(MF) && AFI->getCalleeSavedStackSize() > 0 &&
MF.getFunction().hasOptSize())
return false;
// 512 is the maximum immediate for stp/ldp that will be used for
// callee-save save/restores
if (StackBumpBytes >= 512 || windowsRequiresStackProbe(MF, StackBumpBytes))
return false;
if (MFI.hasVarSizedObjects())
return false;
if (RegInfo->needsStackRealignment(MF))
return false;
// This isn't strictly necessary, but it simplifies things a bit since the
// current RedZone handling code assumes the SP is adjusted by the
// callee-save save/restore code.
if (canUseRedZone(MF))
return false;
// When there is an SVE area on the stack, always allocate the
// callee-saves and spills/locals separately.
if (getSVEStackSize(MF))
return false;
return true;
}
bool AArch64FrameLowering::shouldCombineCSRLocalStackBumpInEpilogue(
MachineBasicBlock &MBB, unsigned StackBumpBytes) const {
if (!shouldCombineCSRLocalStackBump(*MBB.getParent(), StackBumpBytes))
return false;
if (MBB.empty())
return true;
// Disable combined SP bump if the last instruction is an MTE tag store. It
// is almost always better to merge SP adjustment into those instructions.
MachineBasicBlock::iterator LastI = MBB.getFirstTerminator();
MachineBasicBlock::iterator Begin = MBB.begin();
while (LastI != Begin) {
--LastI;
if (LastI->isTransient())
continue;
if (!LastI->getFlag(MachineInstr::FrameDestroy))
break;
}
switch (LastI->getOpcode()) {
case AArch64::STGloop:
case AArch64::STZGloop:
case AArch64::STGOffset:
case AArch64::STZGOffset:
case AArch64::ST2GOffset:
case AArch64::STZ2GOffset:
return false;
default:
return true;
}
llvm_unreachable("unreachable");
}
// Given a load or a store instruction, generate an appropriate unwinding SEH
// code on Windows.
static MachineBasicBlock::iterator InsertSEH(MachineBasicBlock::iterator MBBI,
const TargetInstrInfo &TII,
MachineInstr::MIFlag Flag) {
unsigned Opc = MBBI->getOpcode();
MachineBasicBlock *MBB = MBBI->getParent();
MachineFunction &MF = *MBB->getParent();
DebugLoc DL = MBBI->getDebugLoc();
unsigned ImmIdx = MBBI->getNumOperands() - 1;
int Imm = MBBI->getOperand(ImmIdx).getImm();
MachineInstrBuilder MIB;
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
switch (Opc) {
default:
llvm_unreachable("No SEH Opcode for this instruction");
case AArch64::LDPDpost:
Imm = -Imm;
LLVM_FALLTHROUGH;
case AArch64::STPDpre: {
unsigned Reg0 = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
unsigned Reg1 = RegInfo->getSEHRegNum(MBBI->getOperand(2).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFRegP_X))
.addImm(Reg0)
.addImm(Reg1)
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
case AArch64::LDPXpost:
Imm = -Imm;
LLVM_FALLTHROUGH;
case AArch64::STPXpre: {
Register Reg0 = MBBI->getOperand(1).getReg();
Register Reg1 = MBBI->getOperand(2).getReg();
if (Reg0 == AArch64::FP && Reg1 == AArch64::LR)
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFPLR_X))
.addImm(Imm * 8)
.setMIFlag(Flag);
else
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveRegP_X))
.addImm(RegInfo->getSEHRegNum(Reg0))
.addImm(RegInfo->getSEHRegNum(Reg1))
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
case AArch64::LDRDpost:
Imm = -Imm;
LLVM_FALLTHROUGH;
case AArch64::STRDpre: {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFReg_X))
.addImm(Reg)
.addImm(Imm)
.setMIFlag(Flag);
break;
}
case AArch64::LDRXpost:
Imm = -Imm;
LLVM_FALLTHROUGH;
case AArch64::STRXpre: {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveReg_X))
.addImm(Reg)
.addImm(Imm)
.setMIFlag(Flag);
break;
}
case AArch64::STPDi:
case AArch64::LDPDi: {
unsigned Reg0 = RegInfo->getSEHRegNum(MBBI->getOperand(0).getReg());
unsigned Reg1 = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFRegP))
.addImm(Reg0)
.addImm(Reg1)
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
case AArch64::STPXi:
case AArch64::LDPXi: {
Register Reg0 = MBBI->getOperand(0).getReg();
Register Reg1 = MBBI->getOperand(1).getReg();
if (Reg0 == AArch64::FP && Reg1 == AArch64::LR)
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFPLR))
.addImm(Imm * 8)
.setMIFlag(Flag);
else
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveRegP))
.addImm(RegInfo->getSEHRegNum(Reg0))
.addImm(RegInfo->getSEHRegNum(Reg1))
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
case AArch64::STRXui:
case AArch64::LDRXui: {
int Reg = RegInfo->getSEHRegNum(MBBI->getOperand(0).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveReg))
.addImm(Reg)
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
case AArch64::STRDui:
case AArch64::LDRDui: {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(0).getReg());
MIB = BuildMI(MF, DL, TII.get(AArch64::SEH_SaveFReg))
.addImm(Reg)
.addImm(Imm * 8)
.setMIFlag(Flag);
break;
}
}
auto I = MBB->insertAfter(MBBI, MIB);
return I;
}
// Fix up the SEH opcode associated with the save/restore instruction.
static void fixupSEHOpcode(MachineBasicBlock::iterator MBBI,
unsigned LocalStackSize) {
MachineOperand *ImmOpnd = nullptr;
unsigned ImmIdx = MBBI->getNumOperands() - 1;
switch (MBBI->getOpcode()) {
default:
llvm_unreachable("Fix the offset in the SEH instruction");
case AArch64::SEH_SaveFPLR:
case AArch64::SEH_SaveRegP:
case AArch64::SEH_SaveReg:
case AArch64::SEH_SaveFRegP:
case AArch64::SEH_SaveFReg:
ImmOpnd = &MBBI->getOperand(ImmIdx);
break;
}
if (ImmOpnd)
ImmOpnd->setImm(ImmOpnd->getImm() + LocalStackSize);
}
// Convert callee-save register save/restore instruction to do stack pointer
// decrement/increment to allocate/deallocate the callee-save stack area by
// converting store/load to use pre/post increment version.
static MachineBasicBlock::iterator convertCalleeSaveRestoreToSPPrePostIncDec(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, const TargetInstrInfo *TII, int CSStackSizeInc,
bool NeedsWinCFI, bool *HasWinCFI, bool InProlog = true) {
// Ignore instructions that do not operate on SP, i.e. shadow call stack
// instructions and associated CFI instruction.
while (MBBI->getOpcode() == AArch64::STRXpost ||
MBBI->getOpcode() == AArch64::LDRXpre ||
MBBI->getOpcode() == AArch64::CFI_INSTRUCTION) {
if (MBBI->getOpcode() != AArch64::CFI_INSTRUCTION)
assert(MBBI->getOperand(0).getReg() != AArch64::SP);
++MBBI;
}
unsigned NewOpc;
int Scale = 1;
switch (MBBI->getOpcode()) {
default:
llvm_unreachable("Unexpected callee-save save/restore opcode!");
case AArch64::STPXi:
NewOpc = AArch64::STPXpre;
Scale = 8;
break;
case AArch64::STPDi:
NewOpc = AArch64::STPDpre;
Scale = 8;
break;
case AArch64::STPQi:
NewOpc = AArch64::STPQpre;
Scale = 16;
break;
case AArch64::STRXui:
NewOpc = AArch64::STRXpre;
break;
case AArch64::STRDui:
NewOpc = AArch64::STRDpre;
break;
case AArch64::STRQui:
NewOpc = AArch64::STRQpre;
break;
case AArch64::LDPXi:
NewOpc = AArch64::LDPXpost;
Scale = 8;
break;
case AArch64::LDPDi:
NewOpc = AArch64::LDPDpost;
Scale = 8;
break;
case AArch64::LDPQi:
NewOpc = AArch64::LDPQpost;
Scale = 16;
break;
case AArch64::LDRXui:
NewOpc = AArch64::LDRXpost;
break;
case AArch64::LDRDui:
NewOpc = AArch64::LDRDpost;
break;
case AArch64::LDRQui:
NewOpc = AArch64::LDRQpost;
break;
}
// Get rid of the SEH code associated with the old instruction.
if (NeedsWinCFI) {
auto SEH = std::next(MBBI);
if (AArch64InstrInfo::isSEHInstruction(*SEH))
SEH->eraseFromParent();
}
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(NewOpc));
MIB.addReg(AArch64::SP, RegState::Define);
// Copy all operands other than the immediate offset.
unsigned OpndIdx = 0;
for (unsigned OpndEnd = MBBI->getNumOperands() - 1; OpndIdx < OpndEnd;
++OpndIdx)
MIB.add(MBBI->getOperand(OpndIdx));
assert(MBBI->getOperand(OpndIdx).getImm() == 0 &&
"Unexpected immediate offset in first/last callee-save save/restore "
"instruction!");
assert(MBBI->getOperand(OpndIdx - 1).getReg() == AArch64::SP &&
"Unexpected base register in callee-save save/restore instruction!");
assert(CSStackSizeInc % Scale == 0);
MIB.addImm(CSStackSizeInc / Scale);
MIB.setMIFlags(MBBI->getFlags());
MIB.setMemRefs(MBBI->memoperands());
// Generate a new SEH code that corresponds to the new instruction.
if (NeedsWinCFI) {
*HasWinCFI = true;
InsertSEH(*MIB, *TII,
InProlog ? MachineInstr::FrameSetup : MachineInstr::FrameDestroy);
}
return std::prev(MBB.erase(MBBI));
}
// Fixup callee-save register save/restore instructions to take into account
// combined SP bump by adding the local stack size to the stack offsets.
static void fixupCalleeSaveRestoreStackOffset(MachineInstr &MI,
uint64_t LocalStackSize,
bool NeedsWinCFI,
bool *HasWinCFI) {
if (AArch64InstrInfo::isSEHInstruction(MI))
return;
unsigned Opc = MI.getOpcode();
// Ignore instructions that do not operate on SP, i.e. shadow call stack
// instructions and associated CFI instruction.
if (Opc == AArch64::STRXpost || Opc == AArch64::LDRXpre ||
Opc == AArch64::CFI_INSTRUCTION) {
if (Opc != AArch64::CFI_INSTRUCTION)
assert(MI.getOperand(0).getReg() != AArch64::SP);
return;
}
unsigned Scale;
switch (Opc) {
case AArch64::STPXi:
case AArch64::STRXui:
case AArch64::STPDi:
case AArch64::STRDui:
case AArch64::LDPXi:
case AArch64::LDRXui:
case AArch64::LDPDi:
case AArch64::LDRDui:
Scale = 8;
break;
case AArch64::STPQi:
case AArch64::STRQui:
case AArch64::LDPQi:
case AArch64::LDRQui:
Scale = 16;
break;
default:
llvm_unreachable("Unexpected callee-save save/restore opcode!");
}
unsigned OffsetIdx = MI.getNumExplicitOperands() - 1;
assert(MI.getOperand(OffsetIdx - 1).getReg() == AArch64::SP &&
"Unexpected base register in callee-save save/restore instruction!");
// Last operand is immediate offset that needs fixing.
MachineOperand &OffsetOpnd = MI.getOperand(OffsetIdx);
// All generated opcodes have scaled offsets.
assert(LocalStackSize % Scale == 0);
OffsetOpnd.setImm(OffsetOpnd.getImm() + LocalStackSize / Scale);
if (NeedsWinCFI) {
*HasWinCFI = true;
auto MBBI = std::next(MachineBasicBlock::iterator(MI));
assert(MBBI != MI.getParent()->end() && "Expecting a valid instruction");
assert(AArch64InstrInfo::isSEHInstruction(*MBBI) &&
"Expecting a SEH instruction");
fixupSEHOpcode(MBBI, LocalStackSize);
}
}
static void adaptForLdStOpt(MachineBasicBlock &MBB,
MachineBasicBlock::iterator FirstSPPopI,
MachineBasicBlock::iterator LastPopI) {
// Sometimes (when we restore in the same order as we save), we can end up
// with code like this:
//
// ldp x26, x25, [sp]
// ldp x24, x23, [sp, #16]
// ldp x22, x21, [sp, #32]
// ldp x20, x19, [sp, #48]
// add sp, sp, #64
//
// In this case, it is always better to put the first ldp at the end, so
// that the load-store optimizer can run and merge the ldp and the add into
// a post-index ldp.
// If we managed to grab the first pop instruction, move it to the end.
if (ReverseCSRRestoreSeq)
MBB.splice(FirstSPPopI, &MBB, LastPopI);
// We should end up with something like this now:
//
// ldp x24, x23, [sp, #16]
// ldp x22, x21, [sp, #32]
// ldp x20, x19, [sp, #48]
// ldp x26, x25, [sp]
// add sp, sp, #64
//
// and the load-store optimizer can merge the last two instructions into:
//
// ldp x26, x25, [sp], #64
//
}
static bool isTargetWindows(const MachineFunction &MF) {
return MF.getSubtarget<AArch64Subtarget>().isTargetWindows();
}
// Convenience function to determine whether I is an SVE callee save.
static bool IsSVECalleeSave(MachineBasicBlock::iterator I) {
switch (I->getOpcode()) {
default:
return false;
case AArch64::STR_ZXI:
case AArch64::STR_PXI:
case AArch64::LDR_ZXI:
case AArch64::LDR_PXI:
return I->getFlag(MachineInstr::FrameSetup) ||
I->getFlag(MachineInstr::FrameDestroy);
}
}
void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.begin();
const MachineFrameInfo &MFI = MF.getFrameInfo();
const Function &F = MF.getFunction();
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
const TargetInstrInfo *TII = Subtarget.getInstrInfo();
MachineModuleInfo &MMI = MF.getMMI();
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
bool needsFrameMoves =
MF.needsFrameMoves() && !MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool HasFP = hasFP(MF);
bool NeedsWinCFI = needsWinCFI(MF);
bool HasWinCFI = false;
auto Cleanup = make_scope_exit([&]() { MF.setHasWinCFI(HasWinCFI); });
bool IsFunclet = MBB.isEHFuncletEntry();
// At this point, we're going to decide whether or not the function uses a
// redzone. In most cases, the function doesn't have a redzone so let's
// assume that's false and set it to true in the case that there's a redzone.
AFI->setHasRedZone(false);
// Debug location must be unknown since the first debug location is used
// to determine the end of the prologue.
DebugLoc DL;
const auto &MFnI = *MF.getInfo<AArch64FunctionInfo>();
if (MFnI.shouldSignReturnAddress()) {
if (MFnI.shouldSignWithBKey()) {
BuildMI(MBB, MBBI, DL, TII->get(AArch64::EMITBKEY))
.setMIFlag(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, DL, TII->get(AArch64::PACIBSP))
.setMIFlag(MachineInstr::FrameSetup);
} else {
BuildMI(MBB, MBBI, DL, TII->get(AArch64::PACIASP))
.setMIFlag(MachineInstr::FrameSetup);
}
unsigned CFIIndex =
MF.addFrameInst(MCCFIInstruction::createNegateRAState(nullptr));
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
// Set tagged base pointer to the requested stack slot.
// Ideally it should match SP value after prologue.
Optional<int> TBPI = AFI->getTaggedBasePointerIndex();
if (TBPI)
AFI->setTaggedBasePointerOffset(-MFI.getObjectOffset(*TBPI));
else
AFI->setTaggedBasePointerOffset(MFI.getStackSize());
const StackOffset &SVEStackSize = getSVEStackSize(MF);
// getStackSize() includes all the locals in its size calculation. We don't
// include these locals when computing the stack size of a funclet, as they
// are allocated in the parent's stack frame and accessed via the frame
// pointer from the funclet. We only save the callee saved registers in the
// funclet, which are really the callee saved registers of the parent
// function, including the funclet.
int64_t NumBytes = IsFunclet ? getWinEHFuncletFrameSize(MF)
: MFI.getStackSize();
if (!AFI->hasStackFrame() && !windowsRequiresStackProbe(MF, NumBytes)) {
assert(!HasFP && "unexpected function without stack frame but with FP");
assert(!SVEStackSize &&
"unexpected function without stack frame but with SVE objects");
// All of the stack allocation is for locals.
AFI->setLocalStackSize(NumBytes);
if (!NumBytes)
return;
// REDZONE: If the stack size is less than 128 bytes, we don't need
// to actually allocate.
if (canUseRedZone(MF)) {
AFI->setHasRedZone(true);
++NumRedZoneFunctions;
} else {
emitFrameOffset(MBB, MBBI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(-NumBytes), TII,
MachineInstr::FrameSetup, false, NeedsWinCFI, &HasWinCFI);
if (!NeedsWinCFI && needsFrameMoves) {
// Label used to tie together the PROLOG_LABEL and the MachineMoves.
MCSymbol *FrameLabel = MMI.getContext().createTempSymbol();
// Encode the stack size of the leaf function.
unsigned CFIIndex = MF.addFrameInst(
MCCFIInstruction::cfiDefCfaOffset(FrameLabel, NumBytes));
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
}
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_PrologEnd))
.setMIFlag(MachineInstr::FrameSetup);
}
return;
}
bool IsWin64 =
Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
unsigned FixedObject = getFixedObjectSize(MF, AFI, IsWin64, IsFunclet);
auto PrologueSaveSize = AFI->getCalleeSavedStackSize() + FixedObject;
// All of the remaining stack allocations are for locals.
AFI->setLocalStackSize(NumBytes - PrologueSaveSize);
bool CombineSPBump = shouldCombineCSRLocalStackBump(MF, NumBytes);
if (CombineSPBump) {
assert(!SVEStackSize && "Cannot combine SP bump with SVE");
emitFrameOffset(MBB, MBBI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(-NumBytes), TII,
MachineInstr::FrameSetup, false, NeedsWinCFI, &HasWinCFI);
NumBytes = 0;
} else if (PrologueSaveSize != 0) {
MBBI = convertCalleeSaveRestoreToSPPrePostIncDec(
MBB, MBBI, DL, TII, -PrologueSaveSize, NeedsWinCFI, &HasWinCFI);
NumBytes -= PrologueSaveSize;
}
assert(NumBytes >= 0 && "Negative stack allocation size!?");
// Move past the saves of the callee-saved registers, fixing up the offsets
// and pre-inc if we decided to combine the callee-save and local stack
// pointer bump above.
MachineBasicBlock::iterator End = MBB.end();
while (MBBI != End && MBBI->getFlag(MachineInstr::FrameSetup) &&
!IsSVECalleeSave(MBBI)) {
if (CombineSPBump)
fixupCalleeSaveRestoreStackOffset(*MBBI, AFI->getLocalStackSize(),
NeedsWinCFI, &HasWinCFI);
++MBBI;
}
// For funclets the FP belongs to the containing function.
if (!IsFunclet && HasFP) {
// Only set up FP if we actually need to.
int64_t FPOffset = AFI->getCalleeSaveBaseToFrameRecordOffset();
if (CombineSPBump)
FPOffset += AFI->getLocalStackSize();
// Issue sub fp, sp, FPOffset or
// mov fp,sp when FPOffset is zero.
// Note: All stores of callee-saved registers are marked as "FrameSetup".
// This code marks the instruction(s) that set the FP also.
emitFrameOffset(MBB, MBBI, DL, AArch64::FP, AArch64::SP,
StackOffset::getFixed(FPOffset), TII,
MachineInstr::FrameSetup, false, NeedsWinCFI, &HasWinCFI);
}
if (windowsRequiresStackProbe(MF, NumBytes)) {
uint64_t NumWords = NumBytes >> 4;
if (NeedsWinCFI) {
HasWinCFI = true;
// alloc_l can hold at most 256MB, so assume that NumBytes doesn't
// exceed this amount. We need to move at most 2^24 - 1 into x15.
// This is at most two instructions, MOVZ follwed by MOVK.
// TODO: Fix to use multiple stack alloc unwind codes for stacks
// exceeding 256MB in size.
if (NumBytes >= (1 << 28))
report_fatal_error("Stack size cannot exceed 256MB for stack "
"unwinding purposes");
uint32_t LowNumWords = NumWords & 0xFFFF;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVZXi), AArch64::X15)
.addImm(LowNumWords)
.addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, 0))
.setMIFlag(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
if ((NumWords & 0xFFFF0000) != 0) {
BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVKXi), AArch64::X15)
.addReg(AArch64::X15)
.addImm((NumWords & 0xFFFF0000) >> 16) // High half
.addImm(AArch64_AM::getShifterImm(AArch64_AM::LSL, 16))
.setMIFlag(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
}
} else {
BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVi64imm), AArch64::X15)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup);
}
switch (MF.getTarget().getCodeModel()) {
case CodeModel::Tiny:
case CodeModel::Small:
case CodeModel::Medium:
case CodeModel::Kernel:
BuildMI(MBB, MBBI, DL, TII->get(AArch64::BL))
.addExternalSymbol("__chkstk")
.addReg(AArch64::X15, RegState::Implicit)
.addReg(AArch64::X16, RegState::Implicit | RegState::Define | RegState::Dead)
.addReg(AArch64::X17, RegState::Implicit | RegState::Define | RegState::Dead)
.addReg(AArch64::NZCV, RegState::Implicit | RegState::Define | RegState::Dead)
.setMIFlags(MachineInstr::FrameSetup);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
}
break;
case CodeModel::Large:
BuildMI(MBB, MBBI, DL, TII->get(AArch64::MOVaddrEXT))
.addReg(AArch64::X16, RegState::Define)
.addExternalSymbol("__chkstk")
.addExternalSymbol("__chkstk")
.setMIFlags(MachineInstr::FrameSetup);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
}
BuildMI(MBB, MBBI, DL, TII->get(getBLRCallOpcode(MF)))
.addReg(AArch64::X16, RegState::Kill)
.addReg(AArch64::X15, RegState::Implicit | RegState::Define)
.addReg(AArch64::X16, RegState::Implicit | RegState::Define | RegState::Dead)
.addReg(AArch64::X17, RegState::Implicit | RegState::Define | RegState::Dead)
.addReg(AArch64::NZCV, RegState::Implicit | RegState::Define | RegState::Dead)
.setMIFlags(MachineInstr::FrameSetup);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
}
break;
}
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SUBXrx64), AArch64::SP)
.addReg(AArch64::SP, RegState::Kill)
.addReg(AArch64::X15, RegState::Kill)
.addImm(AArch64_AM::getArithExtendImm(AArch64_AM::UXTX, 4))
.setMIFlags(MachineInstr::FrameSetup);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_StackAlloc))
.addImm(NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
}
NumBytes = 0;
}
StackOffset AllocateBefore = SVEStackSize, AllocateAfter = {};
MachineBasicBlock::iterator CalleeSavesBegin = MBBI, CalleeSavesEnd = MBBI;
// Process the SVE callee-saves to determine what space needs to be
// allocated.
if (int64_t CalleeSavedSize = AFI->getSVECalleeSavedStackSize()) {
// Find callee save instructions in frame.
CalleeSavesBegin = MBBI;
assert(IsSVECalleeSave(CalleeSavesBegin) && "Unexpected instruction");
while (IsSVECalleeSave(MBBI) && MBBI != MBB.getFirstTerminator())
++MBBI;
CalleeSavesEnd = MBBI;
AllocateBefore = StackOffset::getScalable(CalleeSavedSize);
AllocateAfter = SVEStackSize - AllocateBefore;
}
// Allocate space for the callee saves (if any).
emitFrameOffset(MBB, CalleeSavesBegin, DL, AArch64::SP, AArch64::SP,
-AllocateBefore, TII,
MachineInstr::FrameSetup);
// Finally allocate remaining SVE stack space.
emitFrameOffset(MBB, CalleeSavesEnd, DL, AArch64::SP, AArch64::SP,
-AllocateAfter, TII,
MachineInstr::FrameSetup);
// Allocate space for the rest of the frame.
if (NumBytes) {
// Alignment is required for the parent frame, not the funclet
const bool NeedsRealignment =
!IsFunclet && RegInfo->needsStackRealignment(MF);
unsigned scratchSPReg = AArch64::SP;
if (NeedsRealignment) {
scratchSPReg = findScratchNonCalleeSaveRegister(&MBB);
assert(scratchSPReg != AArch64::NoRegister);
}
// If we're a leaf function, try using the red zone.
if (!canUseRedZone(MF))
// FIXME: in the case of dynamic re-alignment, NumBytes doesn't have
// the correct value here, as NumBytes also includes padding bytes,
// which shouldn't be counted here.
emitFrameOffset(MBB, MBBI, DL, scratchSPReg, AArch64::SP,
StackOffset::getFixed(-NumBytes), TII,
MachineInstr::FrameSetup, false, NeedsWinCFI, &HasWinCFI);
if (NeedsRealignment) {
const unsigned NrBitsToZero = Log2(MFI.getMaxAlign());
assert(NrBitsToZero > 1);
assert(scratchSPReg != AArch64::SP);
// SUB X9, SP, NumBytes
// -- X9 is temporary register, so shouldn't contain any live data here,
// -- free to use. This is already produced by emitFrameOffset above.
// AND SP, X9, 0b11111...0000
// The logical immediates have a non-trivial encoding. The following
// formula computes the encoded immediate with all ones but
// NrBitsToZero zero bits as least significant bits.
uint32_t andMaskEncoded = (1 << 12) // = N
| ((64 - NrBitsToZero) << 6) // immr
| ((64 - NrBitsToZero - 1) << 0); // imms
BuildMI(MBB, MBBI, DL, TII->get(AArch64::ANDXri), AArch64::SP)
.addReg(scratchSPReg, RegState::Kill)
.addImm(andMaskEncoded);
AFI->setStackRealigned(true);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_StackAlloc))
.addImm(NumBytes & andMaskEncoded)
.setMIFlag(MachineInstr::FrameSetup);
}
}
}
// If we need a base pointer, set it up here. It's whatever the value of the
// stack pointer is at this point. Any variable size objects will be allocated
// after this, so we can still use the base pointer to reference locals.
//
// FIXME: Clarify FrameSetup flags here.
// Note: Use emitFrameOffset() like above for FP if the FrameSetup flag is
// needed.
// For funclets the BP belongs to the containing function.
if (!IsFunclet && RegInfo->hasBasePointer(MF)) {
TII->copyPhysReg(MBB, MBBI, DL, RegInfo->getBaseRegister(), AArch64::SP,
false);
if (NeedsWinCFI) {
HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
}
}
// The very last FrameSetup instruction indicates the end of prologue. Emit a
// SEH opcode indicating the prologue end.
if (NeedsWinCFI && HasWinCFI) {
BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_PrologEnd))
.setMIFlag(MachineInstr::FrameSetup);
}
// SEH funclets are passed the frame pointer in X1. If the parent
// function uses the base register, then the base register is used
// directly, and is not retrieved from X1.
if (IsFunclet && F.hasPersonalityFn()) {
EHPersonality Per = classifyEHPersonality(F.getPersonalityFn());
if (isAsynchronousEHPersonality(Per)) {
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::COPY), AArch64::FP)
.addReg(AArch64::X1)
.setMIFlag(MachineInstr::FrameSetup);
MBB.addLiveIn(AArch64::X1);
}
}
if (needsFrameMoves) {
// An example of the prologue:
//
// .globl __foo
// .align 2
// __foo:
// Ltmp0:
// .cfi_startproc
// .cfi_personality 155, ___gxx_personality_v0
// Leh_func_begin:
// .cfi_lsda 16, Lexception33
//
// stp xa,bx, [sp, -#offset]!
// ...
// stp x28, x27, [sp, #offset-32]
// stp fp, lr, [sp, #offset-16]
// add fp, sp, #offset - 16
// sub sp, sp, #1360
//
// The Stack:
// +-------------------------------------------+
// 10000 | ........ | ........ | ........ | ........ |
// 10004 | ........ | ........ | ........ | ........ |
// +-------------------------------------------+
// 10008 | ........ | ........ | ........ | ........ |
// 1000c | ........ | ........ | ........ | ........ |
// +===========================================+
// 10010 | X28 Register |
// 10014 | X28 Register |
// +-------------------------------------------+
// 10018 | X27 Register |
// 1001c | X27 Register |
// +===========================================+
// 10020 | Frame Pointer |
// 10024 | Frame Pointer |
// +-------------------------------------------+
// 10028 | Link Register |
// 1002c | Link Register |
// +===========================================+
// 10030 | ........ | ........ | ........ | ........ |
// 10034 | ........ | ........ | ........ | ........ |
// +-------------------------------------------+
// 10038 | ........ | ........ | ........ | ........ |
// 1003c | ........ | ........ | ........ | ........ |
// +-------------------------------------------+
//
// [sp] = 10030 :: >>initial value<<
// sp = 10020 :: stp fp, lr, [sp, #-16]!
// fp = sp == 10020 :: mov fp, sp
// [sp] == 10020 :: stp x28, x27, [sp, #-16]!
// sp == 10010 :: >>final value<<
//
// The frame pointer (w29) points to address 10020. If we use an offset of
// '16' from 'w29', we get the CFI offsets of -8 for w30, -16 for w29, -24
// for w27, and -32 for w28:
//
// Ltmp1:
// .cfi_def_cfa w29, 16
// Ltmp2:
// .cfi_offset w30, -8
// Ltmp3:
// .cfi_offset w29, -16
// Ltmp4:
// .cfi_offset w27, -24
// Ltmp5:
// .cfi_offset w28, -32
if (HasFP) {
const int OffsetToFirstCalleeSaveFromFP =
AFI->getCalleeSaveBaseToFrameRecordOffset() -
AFI->getCalleeSavedStackSize();
Register FramePtr = RegInfo->getFrameRegister(MF);
// Define the current CFA rule to use the provided FP.
unsigned Reg = RegInfo->getDwarfRegNum(FramePtr, true);
unsigned CFIIndex = MF.addFrameInst(
MCCFIInstruction::cfiDefCfa(nullptr, Reg, FixedObject - OffsetToFirstCalleeSaveFromFP));
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
} else {
unsigned CFIIndex;
if (SVEStackSize) {
const TargetSubtargetInfo &STI = MF.getSubtarget();
const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
StackOffset TotalSize =
SVEStackSize + StackOffset::getFixed((int64_t)MFI.getStackSize());
CFIIndex = MF.addFrameInst(createDefCFAExpressionFromSP(TRI, TotalSize));
} else {
// Encode the stack size of the leaf function.
CFIIndex = MF.addFrameInst(
MCCFIInstruction::cfiDefCfaOffset(nullptr, MFI.getStackSize()));
}
BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
// Now emit the moves for whatever callee saved regs we have (including FP,
// LR if those are saved).
emitCalleeSavedFrameMoves(MBB, MBBI);
}
}
static void InsertReturnAddressAuth(MachineFunction &MF,
MachineBasicBlock &MBB) {
const auto &MFI = *MF.getInfo<AArch64FunctionInfo>();
if (!MFI.shouldSignReturnAddress())
return;
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
const TargetInstrInfo *TII = Subtarget.getInstrInfo();
MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
DebugLoc DL;
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
// The AUTIASP instruction assembles to a hint instruction before v8.3a so
// this instruction can safely used for any v8a architecture.
// From v8.3a onwards there are optimised authenticate LR and return
// instructions, namely RETA{A,B}, that can be used instead.
if (Subtarget.hasPAuth() && MBBI != MBB.end() &&
MBBI->getOpcode() == AArch64::RET_ReallyLR) {
BuildMI(MBB, MBBI, DL,
TII->get(MFI.shouldSignWithBKey() ? AArch64::RETAB : AArch64::RETAA))
.copyImplicitOps(*MBBI);
MBB.erase(MBBI);
} else {
BuildMI(
MBB, MBBI, DL,
TII->get(MFI.shouldSignWithBKey() ? AArch64::AUTIBSP : AArch64::AUTIASP))
.setMIFlag(MachineInstr::FrameDestroy);
}
}
static bool isFuncletReturnInstr(const MachineInstr &MI) {
switch (MI.getOpcode()) {
default:
return false;
case AArch64::CATCHRET:
case AArch64::CLEANUPRET:
return true;
}
}
void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
MachineFrameInfo &MFI = MF.getFrameInfo();
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
const TargetInstrInfo *TII = Subtarget.getInstrInfo();
DebugLoc DL;
bool NeedsWinCFI = needsWinCFI(MF);
bool HasWinCFI = false;
bool IsFunclet = false;
auto WinCFI = make_scope_exit([&]() { assert(HasWinCFI == MF.hasWinCFI()); });
if (MBB.end() != MBBI) {
DL = MBBI->getDebugLoc();
IsFunclet = isFuncletReturnInstr(*MBBI);
}
int64_t NumBytes = IsFunclet ? getWinEHFuncletFrameSize(MF)
: MFI.getStackSize();
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
// Initial and residual are named for consistency with the prologue. Note that
// in the epilogue, the residual adjustment is executed first.
uint64_t ArgumentPopSize = getArgumentPopSize(MF, MBB);
// The stack frame should be like below,
//
// ---------------------- ---
// | | |
// | BytesInStackArgArea| CalleeArgStackSize
// | (NumReusableBytes) | (of tail call)
// | | ---
// | | |
// ---------------------| --- |
// | | | |
// | CalleeSavedReg | | |
// | (CalleeSavedStackSize)| | |
// | | | |
// ---------------------| | NumBytes
// | | StackSize (StackAdjustUp)
// | LocalStackSize | | |
// | (covering callee | | |
// | args) | | |
// | | | |
// ---------------------- --- ---
//
// So NumBytes = StackSize + BytesInStackArgArea - CalleeArgStackSize
// = StackSize + ArgumentPopSize
//
// AArch64TargetLowering::LowerCall figures out ArgumentPopSize and keeps
// it as the 2nd argument of AArch64ISD::TC_RETURN.
auto Cleanup = make_scope_exit([&] { InsertReturnAddressAuth(MF, MBB); });
bool IsWin64 =
Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
unsigned FixedObject = getFixedObjectSize(MF, AFI, IsWin64, IsFunclet);
uint64_t AfterCSRPopSize = ArgumentPopSize;
auto PrologueSaveSize = AFI->getCalleeSavedStackSize() + FixedObject;
// We cannot rely on the local stack size set in emitPrologue if the function
// has funclets, as funclets have different local stack size requirements, and
// the current value set in emitPrologue may be that of the containing
// function.
if (MF.hasEHFunclets())
AFI->setLocalStackSize(NumBytes - PrologueSaveSize);
bool CombineSPBump = shouldCombineCSRLocalStackBumpInEpilogue(MBB, NumBytes);
// Assume we can't combine the last pop with the sp restore.
if (!CombineSPBump && PrologueSaveSize != 0) {
MachineBasicBlock::iterator Pop = std::prev(MBB.getFirstTerminator());
while (AArch64InstrInfo::isSEHInstruction(*Pop))
Pop = std::prev(Pop);
// Converting the last ldp to a post-index ldp is valid only if the last
// ldp's offset is 0.
const MachineOperand &OffsetOp = Pop->getOperand(Pop->getNumOperands() - 1);
// If the offset is 0, convert it to a post-index ldp.
if (OffsetOp.getImm() == 0)
convertCalleeSaveRestoreToSPPrePostIncDec(
MBB, Pop, DL, TII, PrologueSaveSize, NeedsWinCFI, &HasWinCFI, false);
else {
// If not, make sure to emit an add after the last ldp.
// We're doing this by transfering the size to be restored from the
// adjustment *before* the CSR pops to the adjustment *after* the CSR
// pops.
AfterCSRPopSize += PrologueSaveSize;
}
}
// Move past the restores of the callee-saved registers.
// If we plan on combining the sp bump of the local stack size and the callee
// save stack size, we might need to adjust the CSR save and restore offsets.
MachineBasicBlock::iterator LastPopI = MBB.getFirstTerminator();
MachineBasicBlock::iterator Begin = MBB.begin();
while (LastPopI != Begin) {
--LastPopI;
if (!LastPopI->getFlag(MachineInstr::FrameDestroy) ||
IsSVECalleeSave(LastPopI)) {
++LastPopI;
break;
} else if (CombineSPBump)
fixupCalleeSaveRestoreStackOffset(*LastPopI, AFI->getLocalStackSize(),
NeedsWinCFI, &HasWinCFI);
}
if (MF.hasWinCFI()) {
// If the prologue didn't contain any SEH opcodes and didn't set the
// MF.hasWinCFI() flag, assume the epilogue won't either, and skip the
// EpilogStart - to avoid generating CFI for functions that don't need it.
// (And as we didn't generate any prologue at all, it would be asymmetrical
// to the epilogue.) By the end of the function, we assert that
// HasWinCFI is equal to MF.hasWinCFI(), to verify this assumption.
HasWinCFI = true;
BuildMI(MBB, LastPopI, DL, TII->get(AArch64::SEH_EpilogStart))
.setMIFlag(MachineInstr::FrameDestroy);
}
const StackOffset &SVEStackSize = getSVEStackSize(MF);
// If there is a single SP update, insert it before the ret and we're done.
if (CombineSPBump) {
assert(!SVEStackSize && "Cannot combine SP bump with SVE");
emitFrameOffset(MBB, MBB.getFirstTerminator(), DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(NumBytes + (int64_t)AfterCSRPopSize),
TII, MachineInstr::FrameDestroy, false, NeedsWinCFI,
&HasWinCFI);
if (HasWinCFI)
BuildMI(MBB, MBB.getFirstTerminator(), DL,
TII->get(AArch64::SEH_EpilogEnd))
.setMIFlag(MachineInstr::FrameDestroy);
return;
}
NumBytes -= PrologueSaveSize;
assert(NumBytes >= 0 && "Negative stack allocation size!?");
// Process the SVE callee-saves to determine what space needs to be
// deallocated.
StackOffset DeallocateBefore = {}, DeallocateAfter = SVEStackSize;
MachineBasicBlock::iterator RestoreBegin = LastPopI, RestoreEnd = LastPopI;
if (int64_t CalleeSavedSize = AFI->getSVECalleeSavedStackSize()) {
RestoreBegin = std::prev(RestoreEnd);
while (RestoreBegin != MBB.begin() &&
IsSVECalleeSave(std::prev(RestoreBegin)))
--RestoreBegin;
assert(IsSVECalleeSave(RestoreBegin) &&
IsSVECalleeSave(std::prev(RestoreEnd)) && "Unexpected instruction");
StackOffset CalleeSavedSizeAsOffset =
StackOffset::getScalable(CalleeSavedSize);
DeallocateBefore = SVEStackSize - CalleeSavedSizeAsOffset;
DeallocateAfter = CalleeSavedSizeAsOffset;
}
// Deallocate the SVE area.
if (SVEStackSize) {
if (AFI->isStackRealigned()) {
if (int64_t CalleeSavedSize = AFI->getSVECalleeSavedStackSize())
// Set SP to start of SVE callee-save area from which they can
// be reloaded. The code below will deallocate the stack space
// space by moving FP -> SP.
emitFrameOffset(MBB, RestoreBegin, DL, AArch64::SP, AArch64::FP,
StackOffset::getScalable(-CalleeSavedSize), TII,
MachineInstr::FrameDestroy);
} else {
if (AFI->getSVECalleeSavedStackSize()) {
// Deallocate the non-SVE locals first before we can deallocate (and
// restore callee saves) from the SVE area.
emitFrameOffset(MBB, RestoreBegin, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(NumBytes), TII,
MachineInstr::FrameDestroy);
NumBytes = 0;
}
emitFrameOffset(MBB, RestoreBegin, DL, AArch64::SP, AArch64::SP,
DeallocateBefore, TII, MachineInstr::FrameDestroy);
emitFrameOffset(MBB, RestoreEnd, DL, AArch64::SP, AArch64::SP,
DeallocateAfter, TII, MachineInstr::FrameDestroy);
}
}
if (!hasFP(MF)) {
bool RedZone = canUseRedZone(MF);
// If this was a redzone leaf function, we don't need to restore the
// stack pointer (but we may need to pop stack args for fastcc).
if (RedZone && AfterCSRPopSize == 0)
return;
bool NoCalleeSaveRestore = PrologueSaveSize == 0;
int64_t StackRestoreBytes = RedZone ? 0 : NumBytes;
if (NoCalleeSaveRestore)
StackRestoreBytes += AfterCSRPopSize;
// If we were able to combine the local stack pop with the argument pop,
// then we're done.
bool Done = NoCalleeSaveRestore || AfterCSRPopSize == 0;
// If we're done after this, make sure to help the load store optimizer.
if (Done)
adaptForLdStOpt(MBB, MBB.getFirstTerminator(), LastPopI);
emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(StackRestoreBytes), TII,
MachineInstr::FrameDestroy, false, NeedsWinCFI, &HasWinCFI);
if (Done) {
if (HasWinCFI) {
BuildMI(MBB, MBB.getFirstTerminator(), DL,
TII->get(AArch64::SEH_EpilogEnd))
.setMIFlag(MachineInstr::FrameDestroy);
}
return;
}
NumBytes = 0;
}
// Restore the original stack pointer.
// FIXME: Rather than doing the math here, we should instead just use
// non-post-indexed loads for the restores if we aren't actually going to
// be able to save any instructions.
if (!IsFunclet && (MFI.hasVarSizedObjects() || AFI->isStackRealigned())) {
emitFrameOffset(
MBB, LastPopI, DL, AArch64::SP, AArch64::FP,
StackOffset::getFixed(-AFI->getCalleeSaveBaseToFrameRecordOffset()),
TII, MachineInstr::FrameDestroy, false, NeedsWinCFI);
} else if (NumBytes)
emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(NumBytes), TII,
MachineInstr::FrameDestroy, false, NeedsWinCFI);
// This must be placed after the callee-save restore code because that code
// assumes the SP is at the same location as it was after the callee-save save
// code in the prologue.
if (AfterCSRPopSize) {
// Find an insertion point for the first ldp so that it goes before the
// shadow call stack epilog instruction. This ensures that the restore of
// lr from x18 is placed after the restore from sp.
auto FirstSPPopI = MBB.getFirstTerminator();
while (FirstSPPopI != Begin) {
auto Prev = std::prev(FirstSPPopI);
if (Prev->getOpcode() != AArch64::LDRXpre ||
Prev->getOperand(0).getReg() == AArch64::SP)
break;
FirstSPPopI = Prev;
}
adaptForLdStOpt(MBB, FirstSPPopI, LastPopI);
emitFrameOffset(MBB, FirstSPPopI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed((int64_t)AfterCSRPopSize), TII,
MachineInstr::FrameDestroy, false, NeedsWinCFI, &HasWinCFI);
}
if (HasWinCFI)
BuildMI(MBB, MBB.getFirstTerminator(), DL, TII->get(AArch64::SEH_EpilogEnd))
.setMIFlag(MachineInstr::FrameDestroy);
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
/// debug info. It's the same as what we use for resolving the code-gen
/// references for now. FIXME: This can go wrong when references are
/// SP-relative and simple call frames aren't used.
StackOffset
AArch64FrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
Register &FrameReg) const {
return resolveFrameIndexReference(
MF, FI, FrameReg,
/*PreferFP=*/
MF.getFunction().hasFnAttribute(Attribute::SanitizeHWAddress),
/*ForSimm=*/false);
}
StackOffset
AArch64FrameLowering::getNonLocalFrameIndexReference(const MachineFunction &MF,
int FI) const {
return StackOffset::getFixed(getSEHFrameIndexOffset(MF, FI));
}
static StackOffset getFPOffset(const MachineFunction &MF,
int64_t ObjectOffset) {
const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
bool IsWin64 =
Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
unsigned FixedObject =
getFixedObjectSize(MF, AFI, IsWin64, /*IsFunclet=*/false);
int64_t CalleeSaveSize = AFI->getCalleeSavedStackSize(MF.getFrameInfo());
int64_t FPAdjust =
CalleeSaveSize - AFI->getCalleeSaveBaseToFrameRecordOffset();
return StackOffset::getFixed(ObjectOffset + FixedObject + FPAdjust);
}
static StackOffset getStackOffset(const MachineFunction &MF,
int64_t ObjectOffset) {
const auto &MFI = MF.getFrameInfo();
return StackOffset::getFixed(ObjectOffset + (int64_t)MFI.getStackSize());
}
// TODO: This function currently does not work for scalable vectors.
int AArch64FrameLowering::getSEHFrameIndexOffset(const MachineFunction &MF,
int FI) const {
const auto *RegInfo = static_cast<const AArch64RegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
int ObjectOffset = MF.getFrameInfo().getObjectOffset(FI);
return RegInfo->getLocalAddressRegister(MF) == AArch64::FP
? getFPOffset(MF, ObjectOffset).getFixed()
: getStackOffset(MF, ObjectOffset).getFixed();
}
StackOffset AArch64FrameLowering::resolveFrameIndexReference(
const MachineFunction &MF, int FI, Register &FrameReg, bool PreferFP,
bool ForSimm) const {
const auto &MFI = MF.getFrameInfo();
int64_t ObjectOffset = MFI.getObjectOffset(FI);
bool isFixed = MFI.isFixedObjectIndex(FI);
bool isSVE = MFI.getStackID(FI) == TargetStackID::ScalableVector;
return resolveFrameOffsetReference(MF, ObjectOffset, isFixed, isSVE, FrameReg,
PreferFP, ForSimm);
}
StackOffset AArch64FrameLowering::resolveFrameOffsetReference(
const MachineFunction &MF, int64_t ObjectOffset, bool isFixed, bool isSVE,
Register &FrameReg, bool PreferFP, bool ForSimm) const {
const auto &MFI = MF.getFrameInfo();
const auto *RegInfo = static_cast<const AArch64RegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
int64_t FPOffset = getFPOffset(MF, ObjectOffset).getFixed();
int64_t Offset = getStackOffset(MF, ObjectOffset).getFixed();
bool isCSR =
!isFixed && ObjectOffset >= -((int)AFI->getCalleeSavedStackSize(MFI));
const StackOffset &SVEStackSize = getSVEStackSize(MF);
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs or a dynamically realigned SP (and thus the SP isn't
// reliable as a base). Make sure useFPForScavengingIndex() does the
// right thing for the emergency spill slot.
bool UseFP = false;
if (AFI->hasStackFrame() && !isSVE) {
// We shouldn't prefer using the FP when there is an SVE area
// in between the FP and the non-SVE locals/spills.
PreferFP &= !SVEStackSize;
// Note: Keeping the following as multiple 'if' statements rather than
// merging to a single expression for readability.
//
// Argument access should always use the FP.
if (isFixed) {
UseFP = hasFP(MF);
} else if (isCSR && RegInfo->needsStackRealignment(MF)) {
// References to the CSR area must use FP if we're re-aligning the stack
// since the dynamically-sized alignment padding is between the SP/BP and
// the CSR area.
assert(hasFP(MF) && "Re-aligned stack must have frame pointer");
UseFP = true;
} else if (hasFP(MF) && !RegInfo->needsStackRealignment(MF)) {
// If the FPOffset is negative and we're producing a signed immediate, we
// have to keep in mind that the available offset range for negative
// offsets is smaller than for positive ones. If an offset is available
// via the FP and the SP, use whichever is closest.
bool FPOffsetFits = !ForSimm || FPOffset >= -256;
PreferFP |= Offset > -FPOffset;
if (MFI.hasVarSizedObjects()) {
// If we have variable sized objects, we can use either FP or BP, as the
// SP offset is unknown. We can use the base pointer if we have one and
// FP is not preferred. If not, we're stuck with using FP.
bool CanUseBP = RegInfo->hasBasePointer(MF);
if (FPOffsetFits && CanUseBP) // Both are ok. Pick the best.
UseFP = PreferFP;
else if (!CanUseBP) // Can't use BP. Forced to use FP.
UseFP = true;
// else we can use BP and FP, but the offset from FP won't fit.
// That will make us scavenge registers which we can probably avoid by
// using BP. If it won't fit for BP either, we'll scavenge anyway.
} else if (FPOffset >= 0) {
// Use SP or FP, whichever gives us the best chance of the offset
// being in range for direct access. If the FPOffset is positive,
// that'll always be best, as the SP will be even further away.
UseFP = true;
} else if (MF.hasEHFunclets() && !RegInfo->hasBasePointer(MF)) {
// Funclets access the locals contained in the parent's stack frame
// via the frame pointer, so we have to use the FP in the parent
// function.
(void) Subtarget;
assert(
Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv()) &&
"Funclets should only be present on Win64");
UseFP = true;
} else {
// We have the choice between FP and (SP or BP).
if (FPOffsetFits && PreferFP) // If FP is the best fit, use it.
UseFP = true;
}
}
}
assert(((isFixed || isCSR) || !RegInfo->needsStackRealignment(MF) || !UseFP) &&
"In the presence of dynamic stack pointer realignment, "
"non-argument/CSR objects cannot be accessed through the frame pointer");
if (isSVE) {
StackOffset FPOffset =
StackOffset::get(-AFI->getCalleeSaveBaseToFrameRecordOffset(), ObjectOffset);
StackOffset SPOffset =
SVEStackSize +
StackOffset::get(MFI.getStackSize() - AFI->getCalleeSavedStackSize(),
ObjectOffset);
// Always use the FP for SVE spills if available and beneficial.
if (hasFP(MF) &&
(SPOffset.getFixed() ||
FPOffset.getScalable() < SPOffset.getScalable() ||
RegInfo->needsStackRealignment(MF))) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
FrameReg = RegInfo->hasBasePointer(MF) ? RegInfo->getBaseRegister()
: (unsigned)AArch64::SP;
return SPOffset;
}
StackOffset ScalableOffset = {};
if (UseFP && !(isFixed || isCSR))
ScalableOffset = -SVEStackSize;
if (!UseFP && (isFixed || isCSR))
ScalableOffset = SVEStackSize;
if (UseFP) {
FrameReg = RegInfo->getFrameRegister(MF);
return StackOffset::getFixed(FPOffset) + ScalableOffset;
}
// Use the base pointer if we have one.
if (RegInfo->hasBasePointer(MF))
FrameReg = RegInfo->getBaseRegister();
else {
assert(!MFI.hasVarSizedObjects() &&
"Can't use SP when we have var sized objects.");
FrameReg = AArch64::SP;
// If we're using the red zone for this function, the SP won't actually
// be adjusted, so the offsets will be negative. They're also all
// within range of the signed 9-bit immediate instructions.
if (canUseRedZone(MF))
Offset -= AFI->getLocalStackSize();
}
return StackOffset::getFixed(Offset) + ScalableOffset;
}
static unsigned getPrologueDeath(MachineFunction &MF, unsigned Reg) {
// Do not set a kill flag on values that are also marked as live-in. This
// happens with the @llvm-returnaddress intrinsic and with arguments passed in
// callee saved registers.
// Omitting the kill flags is conservatively correct even if the live-in
// is not used after all.
bool IsLiveIn = MF.getRegInfo().isLiveIn(Reg);
return getKillRegState(!IsLiveIn);
}
static bool produceCompactUnwindFrame(MachineFunction &MF) {
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
AttributeList Attrs = MF.getFunction().getAttributes();
return Subtarget.isTargetMachO() &&
!(Subtarget.getTargetLowering()->supportSwiftError() &&
Attrs.hasAttrSomewhere(Attribute::SwiftError));
}
static bool invalidateWindowsRegisterPairing(unsigned Reg1, unsigned Reg2,
bool NeedsWinCFI, bool IsFirst) {
// If we are generating register pairs for a Windows function that requires
// EH support, then pair consecutive registers only. There are no unwind
// opcodes for saves/restores of non-consectuve register pairs.
// The unwind opcodes are save_regp, save_regp_x, save_fregp, save_frepg_x,
// save_lrpair.
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
if (Reg2 == AArch64::FP)
return true;
if (!NeedsWinCFI)
return false;
if (Reg2 == Reg1 + 1)
return false;
// If pairing a GPR with LR, the pair can be described by the save_lrpair
// opcode. If this is the first register pair, it would end up with a
// predecrement, but there's no save_lrpair_x opcode, so we can only do this
// if LR is paired with something else than the first register.
// The save_lrpair opcode requires the first register to be an odd one.
if (Reg1 >= AArch64::X19 && Reg1 <= AArch64::X27 &&
(Reg1 - AArch64::X19) % 2 == 0 && Reg2 == AArch64::LR && !IsFirst)
return false;
return true;
}
/// Returns true if Reg1 and Reg2 cannot be paired using a ldp/stp instruction.
/// WindowsCFI requires that only consecutive registers can be paired.
/// LR and FP need to be allocated together when the frame needs to save
/// the frame-record. This means any other register pairing with LR is invalid.
static bool invalidateRegisterPairing(unsigned Reg1, unsigned Reg2,
bool UsesWinAAPCS, bool NeedsWinCFI,
bool NeedsFrameRecord, bool IsFirst) {
if (UsesWinAAPCS)
return invalidateWindowsRegisterPairing(Reg1, Reg2, NeedsWinCFI, IsFirst);
// If we need to store the frame record, don't pair any register
// with LR other than FP.
if (NeedsFrameRecord)
return Reg2 == AArch64::LR;
return false;
}
namespace {
struct RegPairInfo {
unsigned Reg1 = AArch64::NoRegister;
unsigned Reg2 = AArch64::NoRegister;
int FrameIdx;
int Offset;
enum RegType { GPR, FPR64, FPR128, PPR, ZPR } Type;
RegPairInfo() = default;
bool isPaired() const { return Reg2 != AArch64::NoRegister; }
unsigned getScale() const {
switch (Type) {
case PPR:
return 2;
case GPR:
case FPR64:
return 8;
case ZPR:
case FPR128:
return 16;
}
llvm_unreachable("Unsupported type");
}
bool isScalable() const { return Type == PPR || Type == ZPR; }
};
} // end anonymous namespace
static void computeCalleeSaveRegisterPairs(
MachineFunction &MF, ArrayRef<CalleeSavedInfo> CSI,
const TargetRegisterInfo *TRI, SmallVectorImpl<RegPairInfo> &RegPairs,
bool &NeedShadowCallStackProlog, bool NeedsFrameRecord) {
if (CSI.empty())
return;
bool IsWindows = isTargetWindows(MF);
bool NeedsWinCFI = needsWinCFI(MF);
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
MachineFrameInfo &MFI = MF.getFrameInfo();
CallingConv::ID CC = MF.getFunction().getCallingConv();
unsigned Count = CSI.size();
(void)CC;
// MachO's compact unwind format relies on all registers being stored in
// pairs.
assert((!produceCompactUnwindFrame(MF) ||
CC == CallingConv::PreserveMost ||
(Count & 1) == 0) &&
"Odd number of callee-saved regs to spill!");
int ByteOffset = AFI->getCalleeSavedStackSize();
int StackFillDir = -1;
int RegInc = 1;
unsigned FirstReg = 0;
if (NeedsWinCFI) {
// For WinCFI, fill the stack from the bottom up.
ByteOffset = 0;
StackFillDir = 1;
// As the CSI array is reversed to match PrologEpilogInserter, iterate
// backwards, to pair up registers starting from lower numbered registers.
RegInc = -1;
FirstReg = Count - 1;
}
int ScalableByteOffset = AFI->getSVECalleeSavedStackSize();
// When iterating backwards, the loop condition relies on unsigned wraparound.
for (unsigned i = FirstReg; i < Count; i += RegInc) {
RegPairInfo RPI;
RPI.Reg1 = CSI[i].getReg();
if (AArch64::GPR64RegClass.contains(RPI.Reg1))
RPI.Type = RegPairInfo::GPR;
else if (AArch64::FPR64RegClass.contains(RPI.Reg1))
RPI.Type = RegPairInfo::FPR64;
else if (AArch64::FPR128RegClass.contains(RPI.Reg1))
RPI.Type = RegPairInfo::FPR128;
else if (AArch64::ZPRRegClass.contains(RPI.Reg1))
RPI.Type = RegPairInfo::ZPR;
else if (AArch64::PPRRegClass.contains(RPI.Reg1))
RPI.Type = RegPairInfo::PPR;
else
llvm_unreachable("Unsupported register class.");
// Add the next reg to the pair if it is in the same register class.
if (unsigned(i + RegInc) < Count) {
unsigned NextReg = CSI[i + RegInc].getReg();
bool IsFirst = i == FirstReg;
switch (RPI.Type) {
case RegPairInfo::GPR:
if (AArch64::GPR64RegClass.contains(NextReg) &&
!invalidateRegisterPairing(RPI.Reg1, NextReg, IsWindows,
NeedsWinCFI, NeedsFrameRecord, IsFirst))
RPI.Reg2 = NextReg;
break;
case RegPairInfo::FPR64:
if (AArch64::FPR64RegClass.contains(NextReg) &&
!invalidateWindowsRegisterPairing(RPI.Reg1, NextReg, NeedsWinCFI,
IsFirst))
RPI.Reg2 = NextReg;
break;
case RegPairInfo::FPR128:
if (AArch64::FPR128RegClass.contains(NextReg))
RPI.Reg2 = NextReg;
break;
case RegPairInfo::PPR:
case RegPairInfo::ZPR:
break;
}
}
// If either of the registers to be saved is the lr register, it means that
// we also need to save lr in the shadow call stack.
if ((RPI.Reg1 == AArch64::LR || RPI.Reg2 == AArch64::LR) &&
MF.getFunction().hasFnAttribute(Attribute::ShadowCallStack)) {
if (!MF.getSubtarget<AArch64Subtarget>().isXRegisterReserved(18))
report_fatal_error("Must reserve x18 to use shadow call stack");
NeedShadowCallStackProlog = true;
}
// GPRs and FPRs are saved in pairs of 64-bit regs. We expect the CSI
// list to come in sorted by frame index so that we can issue the store
// pair instructions directly. Assert if we see anything otherwise.
//
// The order of the registers in the list is controlled by
// getCalleeSavedRegs(), so they will always be in-order, as well.
assert((!RPI.isPaired() ||
(CSI[i].getFrameIdx() + RegInc == CSI[i + RegInc].getFrameIdx())) &&
"Out of order callee saved regs!");
assert((!RPI.isPaired() || !NeedsFrameRecord || RPI.Reg2 != AArch64::FP ||
RPI.Reg1 == AArch64::LR) &&
"FrameRecord must be allocated together with LR");
// Windows AAPCS has FP and LR reversed.
assert((!RPI.isPaired() || !NeedsFrameRecord || RPI.Reg1 != AArch64::FP ||
RPI.Reg2 == AArch64::LR) &&
"FrameRecord must be allocated together with LR");
// MachO's compact unwind format relies on all registers being stored in
// adjacent register pairs.
assert((!produceCompactUnwindFrame(MF) ||
CC == CallingConv::PreserveMost ||
(RPI.isPaired() &&
((RPI.Reg1 == AArch64::LR && RPI.Reg2 == AArch64::FP) ||
RPI.Reg1 + 1 == RPI.Reg2))) &&
"Callee-save registers not saved as adjacent register pair!");
RPI.FrameIdx = CSI[i].getFrameIdx();
if (NeedsWinCFI &&
RPI.isPaired()) // RPI.FrameIdx must be the lower index of the pair
RPI.FrameIdx = CSI[i + RegInc].getFrameIdx();
int Scale = RPI.getScale();
int OffsetPre = RPI.isScalable() ? ScalableByteOffset : ByteOffset;
assert(OffsetPre % Scale == 0);
if (RPI.isScalable())
ScalableByteOffset += StackFillDir * Scale;
else
ByteOffset += StackFillDir * (RPI.isPaired() ? 2 * Scale : Scale);
assert(!(RPI.isScalable() && RPI.isPaired()) &&
"Paired spill/fill instructions don't exist for SVE vectors");
// Round up size of non-pair to pair size if we need to pad the
// callee-save area to ensure 16-byte alignment.
if (AFI->hasCalleeSaveStackFreeSpace() && !NeedsWinCFI &&
!RPI.isScalable() && RPI.Type != RegPairInfo::FPR128 &&
!RPI.isPaired()) {
ByteOffset += 8 * StackFillDir;
assert(ByteOffset % 16 == 0);
assert(MFI.getObjectAlign(RPI.FrameIdx) <= Align(16));
// A stack frame with a gap looks like this, bottom up:
// d9, d8. x21, gap, x20, x19.
// Set extra alignment on the x21 object (the only unpaired register)
// to create the gap above it.
MFI.setObjectAlignment(RPI.FrameIdx, Align(16));
}
int OffsetPost = RPI.isScalable() ? ScalableByteOffset : ByteOffset;
assert(OffsetPost % Scale == 0);
// If filling top down (default), we want the offset after incrementing it.
// If fillibg bootom up (WinCFI) we need the original offset.
int Offset = NeedsWinCFI ? OffsetPre : OffsetPost;
RPI.Offset = Offset / Scale;
assert(((!RPI.isScalable() && RPI.Offset >= -64 && RPI.Offset <= 63) ||
(RPI.isScalable() && RPI.Offset >= -256 && RPI.Offset <= 255)) &&
"Offset out of bounds for LDP/STP immediate");
// Save the offset to frame record so that the FP register can point to the
// innermost frame record (spilled FP and LR registers).
if (NeedsFrameRecord && ((!IsWindows && RPI.Reg1 == AArch64::LR &&
RPI.Reg2 == AArch64::FP) ||
(IsWindows && RPI.Reg1 == AArch64::FP &&
RPI.Reg2 == AArch64::LR)))
AFI->setCalleeSaveBaseToFrameRecordOffset(Offset);
RegPairs.push_back(RPI);
if (RPI.isPaired())
i += RegInc;
}
if (NeedsWinCFI) {
// If we need an alignment gap in the stack, align the topmost stack
// object. A stack frame with a gap looks like this, bottom up:
// x19, d8. d9, gap.
// Set extra alignment on the topmost stack object (the first element in
// CSI, which goes top down), to create the gap above it.
if (AFI->hasCalleeSaveStackFreeSpace())
MFI.setObjectAlignment(CSI[0].getFrameIdx(), Align(16));
// We iterated bottom up over the registers; flip RegPairs back to top
// down order.
std::reverse(RegPairs.begin(), RegPairs.end());
}
}
bool AArch64FrameLowering::spillCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
bool NeedsWinCFI = needsWinCFI(MF);
DebugLoc DL;
SmallVector<RegPairInfo, 8> RegPairs;
bool NeedShadowCallStackProlog = false;
computeCalleeSaveRegisterPairs(MF, CSI, TRI, RegPairs,
NeedShadowCallStackProlog, hasFP(MF));
const MachineRegisterInfo &MRI = MF.getRegInfo();
if (NeedShadowCallStackProlog) {
// Shadow call stack prolog: str x30, [x18], #8
BuildMI(MBB, MI, DL, TII.get(AArch64::STRXpost))
.addReg(AArch64::X18, RegState::Define)
.addReg(AArch64::LR)
.addReg(AArch64::X18)
.addImm(8)
.setMIFlag(MachineInstr::FrameSetup);
if (NeedsWinCFI)
BuildMI(MBB, MI, DL, TII.get(AArch64::SEH_Nop))
.setMIFlag(MachineInstr::FrameSetup);
if (!MF.getFunction().hasFnAttribute(Attribute::NoUnwind)) {
// Emit a CFI instruction that causes 8 to be subtracted from the value of
// x18 when unwinding past this frame.
static const char CFIInst[] = {
dwarf::DW_CFA_val_expression,
18, // register
2, // length
static_cast<char>(unsigned(dwarf::DW_OP_breg18)),
static_cast<char>(-8) & 0x7f, // addend (sleb128)
};
unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createEscape(
nullptr, StringRef(CFIInst, sizeof(CFIInst))));
BuildMI(MBB, MI, DL, TII.get(AArch64::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlag(MachineInstr::FrameSetup);
}
// This instruction also makes x18 live-in to the entry block.
MBB.addLiveIn(AArch64::X18);
}
for (auto RPII = RegPairs.rbegin(), RPIE = RegPairs.rend(); RPII != RPIE;
++RPII) {
RegPairInfo RPI = *RPII;
unsigned Reg1 = RPI.Reg1;
unsigned Reg2 = RPI.Reg2;
unsigned StrOpc;
// Issue sequence of spills for cs regs. The first spill may be converted
// to a pre-decrement store later by emitPrologue if the callee-save stack
// area allocation can't be combined with the local stack area allocation.
// For example:
// stp x22, x21, [sp, #0] // addImm(+0)
// stp x20, x19, [sp, #16] // addImm(+2)
// stp fp, lr, [sp, #32] // addImm(+4)
// Rationale: This sequence saves uop updates compared to a sequence of
// pre-increment spills like stp xi,xj,[sp,#-16]!
// Note: Similar rationale and sequence for restores in epilog.
unsigned Size;
Align Alignment;
switch (RPI.Type) {
case RegPairInfo::GPR:
StrOpc = RPI.isPaired() ? AArch64::STPXi : AArch64::STRXui;
Size = 8;
Alignment = Align(8);
break;
case RegPairInfo::FPR64:
StrOpc = RPI.isPaired() ? AArch64::STPDi : AArch64::STRDui;
Size = 8;
Alignment = Align(8);
break;
case RegPairInfo::FPR128:
StrOpc = RPI.isPaired() ? AArch64::STPQi : AArch64::STRQui;
Size = 16;
Alignment = Align(16);
break;
case RegPairInfo::ZPR:
StrOpc = AArch64::STR_ZXI;
Size = 16;
Alignment = Align(16);
break;
case RegPairInfo::PPR:
StrOpc = AArch64::STR_PXI;
Size = 2;
Alignment = Align(2);
break;
}
LLVM_DEBUG(dbgs() << "CSR spill: (" << printReg(Reg1, TRI);
if (RPI.isPaired()) dbgs() << ", " << printReg(Reg2, TRI);
dbgs() << ") -> fi#(" << RPI.FrameIdx;
if (RPI.isPaired()) dbgs() << ", " << RPI.FrameIdx + 1;
dbgs() << ")\n");
assert((!NeedsWinCFI || !(Reg1 == AArch64::LR && Reg2 == AArch64::FP)) &&
"Windows unwdinding requires a consecutive (FP,LR) pair");
// Windows unwind codes require consecutive registers if registers are
// paired. Make the switch here, so that the code below will save (x,x+1)
// and not (x+1,x).
unsigned FrameIdxReg1 = RPI.FrameIdx;
unsigned FrameIdxReg2 = RPI.FrameIdx + 1;
if (NeedsWinCFI && RPI.isPaired()) {
std::swap(Reg1, Reg2);
std::swap(FrameIdxReg1, FrameIdxReg2);
}
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StrOpc));
if (!MRI.isReserved(Reg1))
MBB.addLiveIn(Reg1);
if (RPI.isPaired()) {
if (!MRI.isReserved(Reg2))
MBB.addLiveIn(Reg2);
MIB.addReg(Reg2, getPrologueDeath(MF, Reg2));
MIB.addMemOperand(MF.getMachineMemOperand(
MachinePointerInfo::getFixedStack(MF, FrameIdxReg2),
MachineMemOperand::MOStore, Size, Alignment));
}
MIB.addReg(Reg1, getPrologueDeath(MF, Reg1))
.addReg(AArch64::SP)
.addImm(RPI.Offset) // [sp, #offset*scale],
// where factor*scale is implicit
.setMIFlag(MachineInstr::FrameSetup);
MIB.addMemOperand(MF.getMachineMemOperand(
MachinePointerInfo::getFixedStack(MF, FrameIdxReg1),
MachineMemOperand::MOStore, Size, Alignment));
if (NeedsWinCFI)
InsertSEH(MIB, TII, MachineInstr::FrameSetup);
// Update the StackIDs of the SVE stack slots.
MachineFrameInfo &MFI = MF.getFrameInfo();
if (RPI.Type == RegPairInfo::ZPR || RPI.Type == RegPairInfo::PPR)
MFI.setStackID(RPI.FrameIdx, TargetStackID::ScalableVector);
}
return true;
}
bool AArch64FrameLowering::restoreCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
DebugLoc DL;
SmallVector<RegPairInfo, 8> RegPairs;
bool NeedsWinCFI = needsWinCFI(MF);
if (MI != MBB.end())
DL = MI->getDebugLoc();
bool NeedShadowCallStackProlog = false;
computeCalleeSaveRegisterPairs(MF, CSI, TRI, RegPairs,
NeedShadowCallStackProlog, hasFP(MF));
auto EmitMI = [&](const RegPairInfo &RPI) {
unsigned Reg1 = RPI.Reg1;
unsigned Reg2 = RPI.Reg2;
// Issue sequence of restores for cs regs. The last restore may be converted
// to a post-increment load later by emitEpilogue if the callee-save stack
// area allocation can't be combined with the local stack area allocation.
// For example:
// ldp fp, lr, [sp, #32] // addImm(+4)
// ldp x20, x19, [sp, #16] // addImm(+2)
// ldp x22, x21, [sp, #0] // addImm(+0)
// Note: see comment in spillCalleeSavedRegisters()
unsigned LdrOpc;
unsigned Size;
Align Alignment;
switch (RPI.Type) {
case RegPairInfo::GPR:
LdrOpc = RPI.isPaired() ? AArch64::LDPXi : AArch64::LDRXui;
Size = 8;
Alignment = Align(8);
break;
case RegPairInfo::FPR64:
LdrOpc = RPI.isPaired() ? AArch64::LDPDi : AArch64::LDRDui;
Size = 8;
Alignment = Align(8);
break;
case RegPairInfo::FPR128:
LdrOpc = RPI.isPaired() ? AArch64::LDPQi : AArch64::LDRQui;
Size = 16;
Alignment = Align(16);
break;
case RegPairInfo::ZPR:
LdrOpc = AArch64::LDR_ZXI;
Size = 16;
Alignment = Align(16);
break;
case RegPairInfo::PPR:
LdrOpc = AArch64::LDR_PXI;
Size = 2;
Alignment = Align(2);
break;
}
LLVM_DEBUG(dbgs() << "CSR restore: (" << printReg(Reg1, TRI);
if (RPI.isPaired()) dbgs() << ", " << printReg(Reg2, TRI);
dbgs() << ") -> fi#(" << RPI.FrameIdx;
if (RPI.isPaired()) dbgs() << ", " << RPI.FrameIdx + 1;
dbgs() << ")\n");
// Windows unwind codes require consecutive registers if registers are
// paired. Make the switch here, so that the code below will save (x,x+1)
// and not (x+1,x).
unsigned FrameIdxReg1 = RPI.FrameIdx;
unsigned FrameIdxReg2 = RPI.FrameIdx + 1;
if (NeedsWinCFI && RPI.isPaired()) {
std::swap(Reg1, Reg2);
std::swap(FrameIdxReg1, FrameIdxReg2);
}
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(LdrOpc));
if (RPI.isPaired()) {
MIB.addReg(Reg2, getDefRegState(true));
MIB.addMemOperand(MF.getMachineMemOperand(
MachinePointerInfo::getFixedStack(MF, FrameIdxReg2),
MachineMemOperand::MOLoad, Size, Alignment));
}
MIB.addReg(Reg1, getDefRegState(true))
.addReg(AArch64::SP)
.addImm(RPI.Offset) // [sp, #offset*scale]
// where factor*scale is implicit
.setMIFlag(MachineInstr::FrameDestroy);
MIB.addMemOperand(MF.getMachineMemOperand(
MachinePointerInfo::getFixedStack(MF, FrameIdxReg1),
MachineMemOperand::MOLoad, Size, Alignment));
if (NeedsWinCFI)
InsertSEH(MIB, TII, MachineInstr::FrameDestroy);
};
// SVE objects are always restored in reverse order.
for (const RegPairInfo &RPI : reverse(RegPairs))
if (RPI.isScalable())
EmitMI(RPI);
if (ReverseCSRRestoreSeq) {
for (const RegPairInfo &RPI : reverse(RegPairs))
if (!RPI.isScalable())
EmitMI(RPI);
} else
for (const RegPairInfo &RPI : RegPairs)
if (!RPI.isScalable())
EmitMI(RPI);
if (NeedShadowCallStackProlog) {
// Shadow call stack epilog: ldr x30, [x18, #-8]!
BuildMI(MBB, MI, DL, TII.get(AArch64::LDRXpre))
.addReg(AArch64::X18, RegState::Define)
.addReg(AArch64::LR, RegState::Define)
.addReg(AArch64::X18)
.addImm(-8)
.setMIFlag(MachineInstr::FrameDestroy);
}
return true;
}
void AArch64FrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
const AArch64RegisterInfo *RegInfo = static_cast<const AArch64RegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
unsigned UnspilledCSGPR = AArch64::NoRegister;
unsigned UnspilledCSGPRPaired = AArch64::NoRegister;
MachineFrameInfo &MFI = MF.getFrameInfo();
const MCPhysReg *CSRegs = MF.getRegInfo().getCalleeSavedRegs();
unsigned BasePointerReg = RegInfo->hasBasePointer(MF)
? RegInfo->getBaseRegister()
: (unsigned)AArch64::NoRegister;
unsigned ExtraCSSpill = 0;
// Figure out which callee-saved registers to save/restore.
for (unsigned i = 0; CSRegs[i]; ++i) {
const unsigned Reg = CSRegs[i];
// Add the base pointer register to SavedRegs if it is callee-save.
if (Reg == BasePointerReg)
SavedRegs.set(Reg);
bool RegUsed = SavedRegs.test(Reg);
unsigned PairedReg = AArch64::NoRegister;
if (AArch64::GPR64RegClass.contains(Reg) ||
AArch64::FPR64RegClass.contains(Reg) ||
AArch64::FPR128RegClass.contains(Reg))
PairedReg = CSRegs[i ^ 1];
if (!RegUsed) {
if (AArch64::GPR64RegClass.contains(Reg) &&
!RegInfo->isReservedReg(MF, Reg)) {
UnspilledCSGPR = Reg;
UnspilledCSGPRPaired = PairedReg;
}
continue;
}
// MachO's compact unwind format relies on all registers being stored in
// pairs.
// FIXME: the usual format is actually better if unwinding isn't needed.
if (produceCompactUnwindFrame(MF) && PairedReg != AArch64::NoRegister &&
!SavedRegs.test(PairedReg)) {
SavedRegs.set(PairedReg);
if (AArch64::GPR64RegClass.contains(PairedReg) &&
!RegInfo->isReservedReg(MF, PairedReg))
ExtraCSSpill = PairedReg;
}
}
if (MF.getFunction().getCallingConv() == CallingConv::Win64 &&
!Subtarget.isTargetWindows()) {
// For Windows calling convention on a non-windows OS, where X18 is treated
// as reserved, back up X18 when entering non-windows code (marked with the
// Windows calling convention) and restore when returning regardless of
// whether the individual function uses it - it might call other functions
// that clobber it.
SavedRegs.set(AArch64::X18);
}
// Calculates the callee saved stack size.
unsigned CSStackSize = 0;
unsigned SVECSStackSize = 0;
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (unsigned Reg : SavedRegs.set_bits()) {
auto RegSize = TRI->getRegSizeInBits(Reg, MRI) / 8;
if (AArch64::PPRRegClass.contains(Reg) ||
AArch64::ZPRRegClass.contains(Reg))
SVECSStackSize += RegSize;
else
CSStackSize += RegSize;
}
// Save number of saved regs, so we can easily update CSStackSize later.
unsigned NumSavedRegs = SavedRegs.count();
// The frame record needs to be created by saving the appropriate registers
uint64_t EstimatedStackSize = MFI.estimateStackSize(MF);
if (hasFP(MF) ||
windowsRequiresStackProbe(MF, EstimatedStackSize + CSStackSize + 16)) {
SavedRegs.set(AArch64::FP);
SavedRegs.set(AArch64::LR);
}
LLVM_DEBUG(dbgs() << "*** determineCalleeSaves\nSaved CSRs:";
for (unsigned Reg
: SavedRegs.set_bits()) dbgs()
<< ' ' << printReg(Reg, RegInfo);
dbgs() << "\n";);
// If any callee-saved registers are used, the frame cannot be eliminated.
int64_t SVEStackSize =
alignTo(SVECSStackSize + estimateSVEStackObjectOffsets(MFI), 16);
bool CanEliminateFrame = (SavedRegs.count() == 0) && !SVEStackSize;
// The CSR spill slots have not been allocated yet, so estimateStackSize
// won't include them.
unsigned EstimatedStackSizeLimit = estimateRSStackSizeLimit(MF);
// Conservatively always assume BigStack when there are SVE spills.
bool BigStack = SVEStackSize ||
(EstimatedStackSize + CSStackSize) > EstimatedStackSizeLimit;
if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF))
AFI->setHasStackFrame(true);
// Estimate if we might need to scavenge a register at some point in order
// to materialize a stack offset. If so, either spill one additional
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. If we already spilled an extra callee-saved register
// above to keep the number of spills even, we don't need to do anything else
// here.
if (BigStack) {
if (!ExtraCSSpill && UnspilledCSGPR != AArch64::NoRegister) {
LLVM_DEBUG(dbgs() << "Spilling " << printReg(UnspilledCSGPR, RegInfo)
<< " to get a scratch register.\n");
SavedRegs.set(UnspilledCSGPR);
// MachO's compact unwind format relies on all registers being stored in
// pairs, so if we need to spill one extra for BigStack, then we need to
// store the pair.
if (produceCompactUnwindFrame(MF))
SavedRegs.set(UnspilledCSGPRPaired);
ExtraCSSpill = UnspilledCSGPR;
}
// If we didn't find an extra callee-saved register to spill, create
// an emergency spill slot.
if (!ExtraCSSpill || MF.getRegInfo().isPhysRegUsed(ExtraCSSpill)) {
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
const TargetRegisterClass &RC = AArch64::GPR64RegClass;
unsigned Size = TRI->getSpillSize(RC);
Align Alignment = TRI->getSpillAlign(RC);
int FI = MFI.CreateStackObject(Size, Alignment, false);
RS->addScavengingFrameIndex(FI);
LLVM_DEBUG(dbgs() << "No available CS registers, allocated fi#" << FI
<< " as the emergency spill slot.\n");
}
}
// Adding the size of additional 64bit GPR saves.
CSStackSize += 8 * (SavedRegs.count() - NumSavedRegs);
uint64_t AlignedCSStackSize = alignTo(CSStackSize, 16);
LLVM_DEBUG(dbgs() << "Estimated stack frame size: "
<< EstimatedStackSize + AlignedCSStackSize
<< " bytes.\n");
assert((!MFI.isCalleeSavedInfoValid() ||
AFI->getCalleeSavedStackSize() == AlignedCSStackSize) &&
"Should not invalidate callee saved info");
// Round up to register pair alignment to avoid additional SP adjustment
// instructions.
AFI->setCalleeSavedStackSize(AlignedCSStackSize);
AFI->setCalleeSaveStackHasFreeSpace(AlignedCSStackSize != CSStackSize);
AFI->setSVECalleeSavedStackSize(alignTo(SVECSStackSize, 16));
}
bool AArch64FrameLowering::assignCalleeSavedSpillSlots(
MachineFunction &MF, const TargetRegisterInfo *TRI,
std::vector<CalleeSavedInfo> &CSI) const {
bool NeedsWinCFI = needsWinCFI(MF);
// To match the canonical windows frame layout, reverse the list of
// callee saved registers to get them laid out by PrologEpilogInserter
// in the right order. (PrologEpilogInserter allocates stack objects top
// down. Windows canonical prologs store higher numbered registers at
// the top, thus have the CSI array start from the highest registers.)
if (NeedsWinCFI)
std::reverse(CSI.begin(), CSI.end());
// Let the generic code do the rest of the setup.
return false;
}
bool AArch64FrameLowering::enableStackSlotScavenging(
const MachineFunction &MF) const {
const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
return AFI->hasCalleeSaveStackFreeSpace();
}
/// returns true if there are any SVE callee saves.
static bool getSVECalleeSaveSlotRange(const MachineFrameInfo &MFI,
int &Min, int &Max) {
Min = std::numeric_limits<int>::max();
Max = std::numeric_limits<int>::min();
if (!MFI.isCalleeSavedInfoValid())
return false;
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
for (auto &CS : CSI) {
if (AArch64::ZPRRegClass.contains(CS.getReg()) ||
AArch64::PPRRegClass.contains(CS.getReg())) {
assert((Max == std::numeric_limits<int>::min() ||
Max + 1 == CS.getFrameIdx()) &&
"SVE CalleeSaves are not consecutive");
Min = std::min(Min, CS.getFrameIdx());
Max = std::max(Max, CS.getFrameIdx());
}
}
return Min != std::numeric_limits<int>::max();
}
// Process all the SVE stack objects and determine offsets for each
// object. If AssignOffsets is true, the offsets get assigned.
// Fills in the first and last callee-saved frame indices into
// Min/MaxCSFrameIndex, respectively.
// Returns the size of the stack.
static int64_t determineSVEStackObjectOffsets(MachineFrameInfo &MFI,
int &MinCSFrameIndex,
int &MaxCSFrameIndex,
bool AssignOffsets) {
#ifndef NDEBUG
// First process all fixed stack objects.
for (int I = MFI.getObjectIndexBegin(); I != 0; ++I)
assert(MFI.getStackID(I) != TargetStackID::ScalableVector &&
"SVE vectors should never be passed on the stack by value, only by "
"reference.");
#endif
auto Assign = [&MFI](int FI, int64_t Offset) {
LLVM_DEBUG(dbgs() << "alloc FI(" << FI << ") at SP[" << Offset << "]\n");
MFI.setObjectOffset(FI, Offset);
};
int64_t Offset = 0;
// Then process all callee saved slots.
if (getSVECalleeSaveSlotRange(MFI, MinCSFrameIndex, MaxCSFrameIndex)) {
// Assign offsets to the callee save slots.
for (int I = MinCSFrameIndex; I <= MaxCSFrameIndex; ++I) {
Offset += MFI.getObjectSize(I);
Offset = alignTo(Offset, MFI.getObjectAlign(I));
if (AssignOffsets)
Assign(I, -Offset);
}
}
// Ensure that the Callee-save area is aligned to 16bytes.
Offset = alignTo(Offset, Align(16U));
// Create a buffer of SVE objects to allocate and sort it.
SmallVector<int, 8> ObjectsToAllocate;
for (int I = 0, E = MFI.getObjectIndexEnd(); I != E; ++I) {
unsigned StackID = MFI.getStackID(I);
if (StackID != TargetStackID::ScalableVector)
continue;
if (MaxCSFrameIndex >= I && I >= MinCSFrameIndex)
continue;
if (MFI.isDeadObjectIndex(I))
continue;
ObjectsToAllocate.push_back(I);
}
// Allocate all SVE locals and spills
for (unsigned FI : ObjectsToAllocate) {
Align Alignment = MFI.getObjectAlign(FI);
// FIXME: Given that the length of SVE vectors is not necessarily a power of
// two, we'd need to align every object dynamically at runtime if the
// alignment is larger than 16. This is not yet supported.
if (Alignment > Align(16))
report_fatal_error(
"Alignment of scalable vectors > 16 bytes is not yet supported");
Offset = alignTo(Offset + MFI.getObjectSize(FI), Alignment);
if (AssignOffsets)
Assign(FI, -Offset);
}
return Offset;
}
int64_t AArch64FrameLowering::estimateSVEStackObjectOffsets(
MachineFrameInfo &MFI) const {
int MinCSFrameIndex, MaxCSFrameIndex;
return determineSVEStackObjectOffsets(MFI, MinCSFrameIndex, MaxCSFrameIndex, false);
}
int64_t AArch64FrameLowering::assignSVEStackObjectOffsets(
MachineFrameInfo &MFI, int &MinCSFrameIndex, int &MaxCSFrameIndex) const {
return determineSVEStackObjectOffsets(MFI, MinCSFrameIndex, MaxCSFrameIndex,
true);
}
void AArch64FrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF, RegScavenger *RS) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
assert(getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown &&
"Upwards growing stack unsupported");
int MinCSFrameIndex, MaxCSFrameIndex;
int64_t SVEStackSize =
assignSVEStackObjectOffsets(MFI, MinCSFrameIndex, MaxCSFrameIndex);
AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
AFI->setStackSizeSVE(alignTo(SVEStackSize, 16U));
AFI->setMinMaxSVECSFrameIndex(MinCSFrameIndex, MaxCSFrameIndex);
// If this function isn't doing Win64-style C++ EH, we don't need to do
// anything.
if (!MF.hasEHFunclets())
return;
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
WinEHFuncInfo &EHInfo = *MF.getWinEHFuncInfo();
MachineBasicBlock &MBB = MF.front();
auto MBBI = MBB.begin();
while (MBBI != MBB.end() && MBBI->getFlag(MachineInstr::FrameSetup))
++MBBI;
// Create an UnwindHelp object.
// The UnwindHelp object is allocated at the start of the fixed object area
int64_t FixedObject =
getFixedObjectSize(MF, AFI, /*IsWin64*/ true, /*IsFunclet*/ false);
int UnwindHelpFI = MFI.CreateFixedObject(/*Size*/ 8,
/*SPOffset*/ -FixedObject,
/*IsImmutable=*/false);
EHInfo.UnwindHelpFrameIdx = UnwindHelpFI;
// We need to store -2 into the UnwindHelp object at the start of the
// function.
DebugLoc DL;
RS->enterBasicBlockEnd(MBB);
RS->backward(std::prev(MBBI));
unsigned DstReg = RS->FindUnusedReg(&AArch64::GPR64commonRegClass);
assert(DstReg && "There must be a free register after frame setup");
BuildMI(MBB, MBBI, DL, TII.get(AArch64::MOVi64imm), DstReg).addImm(-2);
BuildMI(MBB, MBBI, DL, TII.get(AArch64::STURXi))
.addReg(DstReg, getKillRegState(true))
.addFrameIndex(UnwindHelpFI)
.addImm(0);
}
namespace {
struct TagStoreInstr {
MachineInstr *MI;
int64_t Offset, Size;
explicit TagStoreInstr(MachineInstr *MI, int64_t Offset, int64_t Size)
: MI(MI), Offset(Offset), Size(Size) {}
};
class TagStoreEdit {
MachineFunction *MF;
MachineBasicBlock *MBB;
MachineRegisterInfo *MRI;
// Tag store instructions that are being replaced.
SmallVector<TagStoreInstr, 8> TagStores;
// Combined memref arguments of the above instructions.
SmallVector<MachineMemOperand *, 8> CombinedMemRefs;
// Replace allocation tags in [FrameReg + FrameRegOffset, FrameReg +
// FrameRegOffset + Size) with the address tag of SP.
Register FrameReg;
StackOffset FrameRegOffset;
int64_t Size;
// If not None, move FrameReg to (FrameReg + FrameRegUpdate) at the end.
Optional<int64_t> FrameRegUpdate;
// MIFlags for any FrameReg updating instructions.
unsigned FrameRegUpdateFlags;
// Use zeroing instruction variants.
bool ZeroData;
DebugLoc DL;
void emitUnrolled(MachineBasicBlock::iterator InsertI);
void emitLoop(MachineBasicBlock::iterator InsertI);
public:
TagStoreEdit(MachineBasicBlock *MBB, bool ZeroData)
: MBB(MBB), ZeroData(ZeroData) {
MF = MBB->getParent();
MRI = &MF->getRegInfo();
}
// Add an instruction to be replaced. Instructions must be added in the
// ascending order of Offset, and have to be adjacent.
void addInstruction(TagStoreInstr I) {
assert((TagStores.empty() ||
TagStores.back().Offset + TagStores.back().Size == I.Offset) &&
"Non-adjacent tag store instructions.");
TagStores.push_back(I);
}
void clear() { TagStores.clear(); }
// Emit equivalent code at the given location, and erase the current set of
// instructions. May skip if the replacement is not profitable. May invalidate
// the input iterator and replace it with a valid one.
void emitCode(MachineBasicBlock::iterator &InsertI,
const AArch64FrameLowering *TFI, bool IsLast);
};
void TagStoreEdit::emitUnrolled(MachineBasicBlock::iterator InsertI) {
const AArch64InstrInfo *TII =
MF->getSubtarget<AArch64Subtarget>().getInstrInfo();
const int64_t kMinOffset = -256 * 16;
const int64_t kMaxOffset = 255 * 16;
Register BaseReg = FrameReg;
int64_t BaseRegOffsetBytes = FrameRegOffset.getFixed();
if (BaseRegOffsetBytes < kMinOffset ||
BaseRegOffsetBytes + (Size - Size % 32) > kMaxOffset) {
Register ScratchReg = MRI->createVirtualRegister(&AArch64::GPR64RegClass);
emitFrameOffset(*MBB, InsertI, DL, ScratchReg, BaseReg,
StackOffset::getFixed(BaseRegOffsetBytes), TII);
BaseReg = ScratchReg;
BaseRegOffsetBytes = 0;
}
MachineInstr *LastI = nullptr;
while (Size) {
int64_t InstrSize = (Size > 16) ? 32 : 16;
unsigned Opcode =
InstrSize == 16
? (ZeroData ? AArch64::STZGOffset : AArch64::STGOffset)
: (ZeroData ? AArch64::STZ2GOffset : AArch64::ST2GOffset);
MachineInstr *I = BuildMI(*MBB, InsertI, DL, TII->get(Opcode))
.addReg(AArch64::SP)
.addReg(BaseReg)
.addImm(BaseRegOffsetBytes / 16)
.setMemRefs(CombinedMemRefs);
// A store to [BaseReg, #0] should go last for an opportunity to fold the
// final SP adjustment in the epilogue.
if (BaseRegOffsetBytes == 0)
LastI = I;
BaseRegOffsetBytes += InstrSize;
Size -= InstrSize;
}
if (LastI)
MBB->splice(InsertI, MBB, LastI);
}
void TagStoreEdit::emitLoop(MachineBasicBlock::iterator InsertI) {
const AArch64InstrInfo *TII =
MF->getSubtarget<AArch64Subtarget>().getInstrInfo();
Register BaseReg = FrameRegUpdate
? FrameReg
: MRI->createVirtualRegister(&AArch64::GPR64RegClass);
Register SizeReg = MRI->createVirtualRegister(&AArch64::GPR64RegClass);
emitFrameOffset(*MBB, InsertI, DL, BaseReg, FrameReg, FrameRegOffset, TII);
int64_t LoopSize = Size;
// If the loop size is not a multiple of 32, split off one 16-byte store at
// the end to fold BaseReg update into.
if (FrameRegUpdate && *FrameRegUpdate)
LoopSize -= LoopSize % 32;
MachineInstr *LoopI = BuildMI(*MBB, InsertI, DL,
TII->get(ZeroData ? AArch64::STZGloop_wback
: AArch64::STGloop_wback))
.addDef(SizeReg)
.addDef(BaseReg)
.addImm(LoopSize)
.addReg(BaseReg)
.setMemRefs(CombinedMemRefs);
if (FrameRegUpdate)
LoopI->setFlags(FrameRegUpdateFlags);
int64_t ExtraBaseRegUpdate =
FrameRegUpdate ? (*FrameRegUpdate - FrameRegOffset.getFixed() - Size) : 0;
if (LoopSize < Size) {
assert(FrameRegUpdate);
assert(Size - LoopSize == 16);
// Tag 16 more bytes at BaseReg and update BaseReg.
BuildMI(*MBB, InsertI, DL,
TII->get(ZeroData ? AArch64::STZGPostIndex : AArch64::STGPostIndex))
.addDef(BaseReg)
.addReg(BaseReg)
.addReg(BaseReg)
.addImm(1 + ExtraBaseRegUpdate / 16)
.setMemRefs(CombinedMemRefs)
.setMIFlags(FrameRegUpdateFlags);
} else if (ExtraBaseRegUpdate) {
// Update BaseReg.
BuildMI(
*MBB, InsertI, DL,
TII->get(ExtraBaseRegUpdate > 0 ? AArch64::ADDXri : AArch64::SUBXri))
.addDef(BaseReg)
.addReg(BaseReg)
.addImm(std::abs(ExtraBaseRegUpdate))
.addImm(0)
.setMIFlags(FrameRegUpdateFlags);
}
}
// Check if *II is a register update that can be merged into STGloop that ends
// at (Reg + Size). RemainingOffset is the required adjustment to Reg after the
// end of the loop.
bool canMergeRegUpdate(MachineBasicBlock::iterator II, unsigned Reg,
int64_t Size, int64_t *TotalOffset) {
MachineInstr &MI = *II;
if ((MI.getOpcode() == AArch64::ADDXri ||
MI.getOpcode() == AArch64::SUBXri) &&
MI.getOperand(0).getReg() == Reg && MI.getOperand(1).getReg() == Reg) {
unsigned Shift = AArch64_AM::getShiftValue(MI.getOperand(3).getImm());
int64_t Offset = MI.getOperand(2).getImm() << Shift;
if (MI.getOpcode() == AArch64::SUBXri)
Offset = -Offset;
int64_t AbsPostOffset = std::abs(Offset - Size);
const int64_t kMaxOffset =
0xFFF; // Max encoding for unshifted ADDXri / SUBXri
if (AbsPostOffset <= kMaxOffset && AbsPostOffset % 16 == 0) {
*TotalOffset = Offset;
return true;
}
}
return false;
}
void mergeMemRefs(const SmallVectorImpl<TagStoreInstr> &TSE,
SmallVectorImpl<MachineMemOperand *> &MemRefs) {
MemRefs.clear();
for (auto &TS : TSE) {
MachineInstr *MI = TS.MI;
// An instruction without memory operands may access anything. Be
// conservative and return an empty list.
if (MI->memoperands_empty()) {
MemRefs.clear();
return;
}
MemRefs.append(MI->memoperands_begin(), MI->memoperands_end());
}
}
void TagStoreEdit::emitCode(MachineBasicBlock::iterator &InsertI,
const AArch64FrameLowering *TFI, bool IsLast) {
if (TagStores.empty())
return;
TagStoreInstr &FirstTagStore = TagStores[0];
TagStoreInstr &LastTagStore = TagStores[TagStores.size() - 1];
Size = LastTagStore.Offset - FirstTagStore.Offset + LastTagStore.Size;
DL = TagStores[0].MI->getDebugLoc();
Register Reg;
FrameRegOffset = TFI->resolveFrameOffsetReference(
*MF, FirstTagStore.Offset, false /*isFixed*/, false /*isSVE*/, Reg,
/*PreferFP=*/false, /*ForSimm=*/true);
FrameReg = Reg;
FrameRegUpdate = None;
mergeMemRefs(TagStores, CombinedMemRefs);
LLVM_DEBUG(dbgs() << "Replacing adjacent STG instructions:\n";
for (const auto &Instr
: TagStores) { dbgs() << " " << *Instr.MI; });
// Size threshold where a loop becomes shorter than a linear sequence of
// tagging instructions.
const int kSetTagLoopThreshold = 176;
if (Size < kSetTagLoopThreshold) {
if (TagStores.size() < 2)
return;
emitUnrolled(InsertI);
} else {
MachineInstr *UpdateInstr = nullptr;
int64_t TotalOffset;
if (IsLast) {
// See if we can merge base register update into the STGloop.
// This is done in AArch64LoadStoreOptimizer for "normal" stores,
// but STGloop is way too unusual for that, and also it only
// realistically happens in function epilogue. Also, STGloop is expanded
// before that pass.
if (InsertI != MBB->end() &&
canMergeRegUpdate(InsertI, FrameReg, FrameRegOffset.getFixed() + Size,
&TotalOffset)) {
UpdateInstr = &*InsertI++;
LLVM_DEBUG(dbgs() << "Folding SP update into loop:\n "
<< *UpdateInstr);
}
}
if (!UpdateInstr && TagStores.size() < 2)
return;
if (UpdateInstr) {
FrameRegUpdate = TotalOffset;
FrameRegUpdateFlags = UpdateInstr->getFlags();
}
emitLoop(InsertI);
if (UpdateInstr)
UpdateInstr->eraseFromParent();
}
for (auto &TS : TagStores)
TS.MI->eraseFromParent();
}
bool isMergeableStackTaggingInstruction(MachineInstr &MI, int64_t &Offset,
int64_t &Size, bool &ZeroData) {
MachineFunction &MF = *MI.getParent()->getParent();
const MachineFrameInfo &MFI = MF.getFrameInfo();
unsigned Opcode = MI.getOpcode();
ZeroData = (Opcode == AArch64::STZGloop || Opcode == AArch64::STZGOffset ||
Opcode == AArch64::STZ2GOffset);
if (Opcode == AArch64::STGloop || Opcode == AArch64::STZGloop) {
if (!MI.getOperand(0).isDead() || !MI.getOperand(1).isDead())
return false;
if (!MI.getOperand(2).isImm() || !MI.getOperand(3).isFI())
return false;
Offset = MFI.getObjectOffset(MI.getOperand(3).getIndex());
Size = MI.getOperand(2).getImm();
return true;
}
if (Opcode == AArch64::STGOffset || Opcode == AArch64::STZGOffset)
Size = 16;
else if (Opcode == AArch64::ST2GOffset || Opcode == AArch64::STZ2GOffset)
Size = 32;
else
return false;
if (MI.getOperand(0).getReg() != AArch64::SP || !MI.getOperand(1).isFI())
return false;
Offset = MFI.getObjectOffset(MI.getOperand(1).getIndex()) +
16 * MI.getOperand(2).getImm();
return true;
}
// Detect a run of memory tagging instructions for adjacent stack frame slots,
// and replace them with a shorter instruction sequence:
// * replace STG + STG with ST2G
// * replace STGloop + STGloop with STGloop
// This code needs to run when stack slot offsets are already known, but before
// FrameIndex operands in STG instructions are eliminated.
MachineBasicBlock::iterator tryMergeAdjacentSTG(MachineBasicBlock::iterator II,
const AArch64FrameLowering *TFI,
RegScavenger *RS) {
bool FirstZeroData;
int64_t Size, Offset;
MachineInstr &MI = *II;
MachineBasicBlock *MBB = MI.getParent();
MachineBasicBlock::iterator NextI = ++II;
if (&MI == &MBB->instr_back())
return II;
if (!isMergeableStackTaggingInstruction(MI, Offset, Size, FirstZeroData))
return II;
SmallVector<TagStoreInstr, 4> Instrs;
Instrs.emplace_back(&MI, Offset, Size);
constexpr int kScanLimit = 10;
int Count = 0;
for (MachineBasicBlock::iterator E = MBB->end();
NextI != E && Count < kScanLimit; ++NextI) {
MachineInstr &MI = *NextI;
bool ZeroData;
int64_t Size, Offset;
// Collect instructions that update memory tags with a FrameIndex operand
// and (when applicable) constant size, and whose output registers are dead
// (the latter is almost always the case in practice). Since these
// instructions effectively have no inputs or outputs, we are free to skip
// any non-aliasing instructions in between without tracking used registers.
if (isMergeableStackTaggingInstruction(MI, Offset, Size, ZeroData)) {
if (ZeroData != FirstZeroData)
break;
Instrs.emplace_back(&MI, Offset, Size);
continue;
}
// Only count non-transient, non-tagging instructions toward the scan
// limit.
if (!MI.isTransient())
++Count;
// Just in case, stop before the epilogue code starts.
if (MI.getFlag(MachineInstr::FrameSetup) ||
MI.getFlag(MachineInstr::FrameDestroy))
break;
// Reject anything that may alias the collected instructions.
if (MI.mayLoadOrStore() || MI.hasUnmodeledSideEffects())
break;
}
// New code will be inserted after the last tagging instruction we've found.
MachineBasicBlock::iterator InsertI = Instrs.back().MI;
InsertI++;
llvm::stable_sort(Instrs,
[](const TagStoreInstr &Left, const TagStoreInstr &Right) {
return Left.Offset < Right.Offset;
});
// Make sure that we don't have any overlapping stores.
int64_t CurOffset = Instrs[0].Offset;
for (auto &Instr : Instrs) {
if (CurOffset > Instr.Offset)
return NextI;
CurOffset = Instr.Offset + Instr.Size;
}
// Find contiguous runs of tagged memory and emit shorter instruction
// sequencies for them when possible.
TagStoreEdit TSE(MBB, FirstZeroData);
Optional<int64_t> EndOffset;
for (auto &Instr : Instrs) {
if (EndOffset && *EndOffset != Instr.Offset) {
// Found a gap.
TSE.emitCode(InsertI, TFI, /*IsLast = */ false);
TSE.clear();
}
TSE.addInstruction(Instr);
EndOffset = Instr.Offset + Instr.Size;
}
TSE.emitCode(InsertI, TFI, /*IsLast = */ true);
return InsertI;
}
} // namespace
void AArch64FrameLowering::processFunctionBeforeFrameIndicesReplaced(
MachineFunction &MF, RegScavenger *RS = nullptr) const {
if (StackTaggingMergeSetTag)
for (auto &BB : MF)
for (MachineBasicBlock::iterator II = BB.begin(); II != BB.end();)
II = tryMergeAdjacentSTG(II, this, RS);
}
/// For Win64 AArch64 EH, the offset to the Unwind object is from the SP
/// before the update. This is easily retrieved as it is exactly the offset
/// that is set in processFunctionBeforeFrameFinalized.
StackOffset AArch64FrameLowering::getFrameIndexReferencePreferSP(
const MachineFunction &MF, int FI, Register &FrameReg,
bool IgnoreSPUpdates) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
if (IgnoreSPUpdates) {
LLVM_DEBUG(dbgs() << "Offset from the SP for " << FI << " is "
<< MFI.getObjectOffset(FI) << "\n");
FrameReg = AArch64::SP;
return StackOffset::getFixed(MFI.getObjectOffset(FI));
}
return getFrameIndexReference(MF, FI, FrameReg);
}
/// The parent frame offset (aka dispFrame) is only used on X86_64 to retrieve
/// the parent's frame pointer
unsigned AArch64FrameLowering::getWinEHParentFrameOffset(
const MachineFunction &MF) const {
return 0;
}
/// Funclets only need to account for space for the callee saved registers,
/// as the locals are accounted for in the parent's stack frame.
unsigned AArch64FrameLowering::getWinEHFuncletFrameSize(
const MachineFunction &MF) const {
// This is the size of the pushed CSRs.
unsigned CSSize =
MF.getInfo<AArch64FunctionInfo>()->getCalleeSavedStackSize();
// This is the amount of stack a funclet needs to allocate.
return alignTo(CSSize + MF.getFrameInfo().getMaxCallFrameSize(),
getStackAlign());
}
namespace {
struct FrameObject {
bool IsValid = false;
// Index of the object in MFI.
int ObjectIndex = 0;
// Group ID this object belongs to.
int GroupIndex = -1;
// This object should be placed first (closest to SP).
bool ObjectFirst = false;
// This object's group (which always contains the object with
// ObjectFirst==true) should be placed first.
bool GroupFirst = false;
};
class GroupBuilder {
SmallVector<int, 8> CurrentMembers;
int NextGroupIndex = 0;
std::vector<FrameObject> &Objects;
public:
GroupBuilder(std::vector<FrameObject> &Objects) : Objects(Objects) {}
void AddMember(int Index) { CurrentMembers.push_back(Index); }
void EndCurrentGroup() {
if (CurrentMembers.size() > 1) {
// Create a new group with the current member list. This might remove them
// from their pre-existing groups. That's OK, dealing with overlapping
// groups is too hard and unlikely to make a difference.
LLVM_DEBUG(dbgs() << "group:");
for (int Index : CurrentMembers) {
Objects[Index].GroupIndex = NextGroupIndex;
LLVM_DEBUG(dbgs() << " " << Index);
}
LLVM_DEBUG(dbgs() << "\n");
NextGroupIndex++;
}
CurrentMembers.clear();
}
};
bool FrameObjectCompare(const FrameObject &A, const FrameObject &B) {
// Objects at a lower index are closer to FP; objects at a higher index are
// closer to SP.
//
// For consistency in our comparison, all invalid objects are placed
// at the end. This also allows us to stop walking when we hit the
// first invalid item after it's all sorted.
//
// The "first" object goes first (closest to SP), followed by the members of
// the "first" group.
//
// The rest are sorted by the group index to keep the groups together.
// Higher numbered groups are more likely to be around longer (i.e. untagged
// in the function epilogue and not at some earlier point). Place them closer
// to SP.
//
// If all else equal, sort by the object index to keep the objects in the
// original order.
return std::make_tuple(!A.IsValid, A.ObjectFirst, A.GroupFirst, A.GroupIndex,
A.ObjectIndex) <
std::make_tuple(!B.IsValid, B.ObjectFirst, B.GroupFirst, B.GroupIndex,
B.ObjectIndex);
}
} // namespace
void AArch64FrameLowering::orderFrameObjects(
const MachineFunction &MF, SmallVectorImpl<int> &ObjectsToAllocate) const {
if (!OrderFrameObjects || ObjectsToAllocate.empty())
return;
const MachineFrameInfo &MFI = MF.getFrameInfo();
std::vector<FrameObject> FrameObjects(MFI.getObjectIndexEnd());
for (auto &Obj : ObjectsToAllocate) {
FrameObjects[Obj].IsValid = true;
FrameObjects[Obj].ObjectIndex = Obj;
}
// Identify stack slots that are tagged at the same time.
GroupBuilder GB(FrameObjects);
for (auto &MBB : MF) {
for (auto &MI : MBB) {
if (MI.isDebugInstr())
continue;
int OpIndex;
switch (MI.getOpcode()) {
case AArch64::STGloop:
case AArch64::STZGloop:
OpIndex = 3;
break;
case AArch64::STGOffset:
case AArch64::STZGOffset:
case AArch64::ST2GOffset:
case AArch64::STZ2GOffset:
OpIndex = 1;
break;
default:
OpIndex = -1;
}
int TaggedFI = -1;
if (OpIndex >= 0) {
const MachineOperand &MO = MI.getOperand(OpIndex);
if (MO.isFI()) {
int FI = MO.getIndex();
if (FI >= 0 && FI < MFI.getObjectIndexEnd() &&
FrameObjects[FI].IsValid)
TaggedFI = FI;
}
}
// If this is a stack tagging instruction for a slot that is not part of a
// group yet, either start a new group or add it to the current one.
if (TaggedFI >= 0)
GB.AddMember(TaggedFI);
else
GB.EndCurrentGroup();
}
// Groups should never span multiple basic blocks.
GB.EndCurrentGroup();
}
// If the function's tagged base pointer is pinned to a stack slot, we want to
// put that slot first when possible. This will likely place it at SP + 0,
// and save one instruction when generating the base pointer because IRG does
// not allow an immediate offset.
const AArch64FunctionInfo &AFI = *MF.getInfo<AArch64FunctionInfo>();
Optional<int> TBPI = AFI.getTaggedBasePointerIndex();
if (TBPI) {
FrameObjects[*TBPI].ObjectFirst = true;
FrameObjects[*TBPI].GroupFirst = true;
int FirstGroupIndex = FrameObjects[*TBPI].GroupIndex;
if (FirstGroupIndex >= 0)
for (FrameObject &Object : FrameObjects)
if (Object.GroupIndex == FirstGroupIndex)
Object.GroupFirst = true;
}
llvm::stable_sort(FrameObjects, FrameObjectCompare);
int i = 0;
for (auto &Obj : FrameObjects) {
// All invalid items are sorted at the end, so it's safe to stop.
if (!Obj.IsValid)
break;
ObjectsToAllocate[i++] = Obj.ObjectIndex;
}
LLVM_DEBUG(dbgs() << "Final frame order:\n"; for (auto &Obj
: FrameObjects) {
if (!Obj.IsValid)
break;
dbgs() << " " << Obj.ObjectIndex << ": group " << Obj.GroupIndex;
if (Obj.ObjectFirst)
dbgs() << ", first";
if (Obj.GroupFirst)
dbgs() << ", group-first";
dbgs() << "\n";
});
}
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