457 lines
19 KiB
C
457 lines
19 KiB
C
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//===-- llvm/CodeGen/TargetFrameLowering.h ----------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Interface to describe the layout of a stack frame on the target machine.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_TARGETFRAMELOWERING_H
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#define LLVM_CODEGEN_TARGETFRAMELOWERING_H
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/Support/TypeSize.h"
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#include <vector>
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namespace llvm {
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class BitVector;
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class CalleeSavedInfo;
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class MachineFunction;
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class RegScavenger;
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namespace TargetStackID {
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enum Value {
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Default = 0,
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SGPRSpill = 1,
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ScalableVector = 2,
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NoAlloc = 255
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};
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}
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/// Information about stack frame layout on the target. It holds the direction
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/// of stack growth, the known stack alignment on entry to each function, and
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/// the offset to the locals area.
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///
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/// The offset to the local area is the offset from the stack pointer on
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/// function entry to the first location where function data (local variables,
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/// spill locations) can be stored.
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class TargetFrameLowering {
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public:
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enum StackDirection {
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StackGrowsUp, // Adding to the stack increases the stack address
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StackGrowsDown // Adding to the stack decreases the stack address
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};
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// Maps a callee saved register to a stack slot with a fixed offset.
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struct SpillSlot {
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unsigned Reg;
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int Offset; // Offset relative to stack pointer on function entry.
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};
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struct DwarfFrameBase {
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// The frame base may be either a register (the default), the CFA,
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// or a WebAssembly-specific location description.
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enum FrameBaseKind { Register, CFA, WasmFrameBase } Kind;
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struct WasmFrameBase {
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unsigned Kind; // Wasm local, global, or value stack
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unsigned Index;
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};
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union {
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unsigned Reg;
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struct WasmFrameBase WasmLoc;
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} Location;
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};
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private:
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StackDirection StackDir;
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Align StackAlignment;
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Align TransientStackAlignment;
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int LocalAreaOffset;
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bool StackRealignable;
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public:
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TargetFrameLowering(StackDirection D, Align StackAl, int LAO,
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Align TransAl = Align(1), bool StackReal = true)
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: StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
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LocalAreaOffset(LAO), StackRealignable(StackReal) {}
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virtual ~TargetFrameLowering();
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// These methods return information that describes the abstract stack layout
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// of the target machine.
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/// getStackGrowthDirection - Return the direction the stack grows
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///
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StackDirection getStackGrowthDirection() const { return StackDir; }
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/// getStackAlignment - This method returns the number of bytes to which the
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/// stack pointer must be aligned on entry to a function. Typically, this
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/// is the largest alignment for any data object in the target.
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///
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unsigned getStackAlignment() const { return StackAlignment.value(); }
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/// getStackAlignment - This method returns the number of bytes to which the
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/// stack pointer must be aligned on entry to a function. Typically, this
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/// is the largest alignment for any data object in the target.
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///
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Align getStackAlign() const { return StackAlignment; }
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/// alignSPAdjust - This method aligns the stack adjustment to the correct
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/// alignment.
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///
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int alignSPAdjust(int SPAdj) const {
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if (SPAdj < 0) {
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SPAdj = -alignTo(-SPAdj, StackAlignment);
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} else {
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SPAdj = alignTo(SPAdj, StackAlignment);
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}
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return SPAdj;
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}
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/// getTransientStackAlignment - This method returns the number of bytes to
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/// which the stack pointer must be aligned at all times, even between
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/// calls.
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///
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LLVM_ATTRIBUTE_DEPRECATED(unsigned getTransientStackAlignment() const,
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"Use getTransientStackAlign instead") {
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return TransientStackAlignment.value();
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}
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/// getTransientStackAlignment - This method returns the number of bytes to
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/// which the stack pointer must be aligned at all times, even between
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/// calls.
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///
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Align getTransientStackAlign() const { return TransientStackAlignment; }
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/// isStackRealignable - This method returns whether the stack can be
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/// realigned.
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bool isStackRealignable() const {
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return StackRealignable;
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}
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/// Return the skew that has to be applied to stack alignment under
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/// certain conditions (e.g. stack was adjusted before function \p MF
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/// was called).
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virtual unsigned getStackAlignmentSkew(const MachineFunction &MF) const;
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/// This method returns whether or not it is safe for an object with the
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/// given stack id to be bundled into the local area.
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virtual bool isStackIdSafeForLocalArea(unsigned StackId) const {
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return true;
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}
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/// getOffsetOfLocalArea - This method returns the offset of the local area
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/// from the stack pointer on entrance to a function.
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///
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int getOffsetOfLocalArea() const { return LocalAreaOffset; }
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/// isFPCloseToIncomingSP - Return true if the frame pointer is close to
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/// the incoming stack pointer, false if it is close to the post-prologue
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/// stack pointer.
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virtual bool isFPCloseToIncomingSP() const { return true; }
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/// assignCalleeSavedSpillSlots - Allows target to override spill slot
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/// assignment logic. If implemented, assignCalleeSavedSpillSlots() should
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/// assign frame slots to all CSI entries and return true. If this method
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/// returns false, spill slots will be assigned using generic implementation.
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/// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
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/// CSI.
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virtual bool
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assignCalleeSavedSpillSlots(MachineFunction &MF,
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const TargetRegisterInfo *TRI,
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std::vector<CalleeSavedInfo> &CSI) const {
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return false;
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}
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/// getCalleeSavedSpillSlots - This method returns a pointer to an array of
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/// pairs, that contains an entry for each callee saved register that must be
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/// spilled to a particular stack location if it is spilled.
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///
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/// Each entry in this array contains a <register,offset> pair, indicating the
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/// fixed offset from the incoming stack pointer that each register should be
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/// spilled at. If a register is not listed here, the code generator is
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/// allowed to spill it anywhere it chooses.
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///
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virtual const SpillSlot *
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getCalleeSavedSpillSlots(unsigned &NumEntries) const {
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NumEntries = 0;
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return nullptr;
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}
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/// targetHandlesStackFrameRounding - Returns true if the target is
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/// responsible for rounding up the stack frame (probably at emitPrologue
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/// time).
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virtual bool targetHandlesStackFrameRounding() const {
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return false;
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}
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/// Returns true if the target will correctly handle shrink wrapping.
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virtual bool enableShrinkWrapping(const MachineFunction &MF) const {
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return false;
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}
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/// Returns true if the stack slot holes in the fixed and callee-save stack
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/// area should be used when allocating other stack locations to reduce stack
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/// size.
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virtual bool enableStackSlotScavenging(const MachineFunction &MF) const {
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return false;
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}
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/// Returns true if the target can safely skip saving callee-saved registers
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/// for noreturn nounwind functions.
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virtual bool enableCalleeSaveSkip(const MachineFunction &MF) const;
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/// emitProlog/emitEpilog - These methods insert prolog and epilog code into
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/// the function.
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virtual void emitPrologue(MachineFunction &MF,
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MachineBasicBlock &MBB) const = 0;
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virtual void emitEpilogue(MachineFunction &MF,
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MachineBasicBlock &MBB) const = 0;
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/// With basic block sections, emit callee saved frame moves for basic blocks
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/// that are in a different section.
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virtual void
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emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI) const {}
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virtual void emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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bool IsPrologue) const {}
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/// Replace a StackProbe stub (if any) with the actual probe code inline
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virtual void inlineStackProbe(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// Adjust the prologue to have the function use segmented stacks. This works
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/// by adding a check even before the "normal" function prologue.
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virtual void adjustForSegmentedStacks(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// Adjust the prologue to add Erlang Run-Time System (ERTS) specific code in
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/// the assembly prologue to explicitly handle the stack.
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virtual void adjustForHiPEPrologue(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const {}
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/// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
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/// saved registers and returns true if it isn't possible / profitable to do
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/// so by issuing a series of store instructions via
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/// storeRegToStackSlot(). Returns false otherwise.
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virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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ArrayRef<CalleeSavedInfo> CSI,
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const TargetRegisterInfo *TRI) const {
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return false;
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}
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/// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
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/// saved registers and returns true if it isn't possible / profitable to do
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/// so by issuing a series of load instructions via loadRegToStackSlot().
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/// If it returns true, and any of the registers in CSI is not restored,
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/// it sets the corresponding Restored flag in CSI to false.
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/// Returns false otherwise.
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virtual bool
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restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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MutableArrayRef<CalleeSavedInfo> CSI,
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const TargetRegisterInfo *TRI) const {
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return false;
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}
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/// Return true if the target wants to keep the frame pointer regardless of
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/// the function attribute "frame-pointer".
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virtual bool keepFramePointer(const MachineFunction &MF) const {
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return false;
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}
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/// hasFP - Return true if the specified function should have a dedicated
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/// frame pointer register. For most targets this is true only if the function
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/// has variable sized allocas or if frame pointer elimination is disabled.
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virtual bool hasFP(const MachineFunction &MF) const = 0;
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/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
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/// not required, we reserve argument space for call sites in the function
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/// immediately on entry to the current function. This eliminates the need for
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/// add/sub sp brackets around call sites. Returns true if the call frame is
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/// included as part of the stack frame.
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virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
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return !hasFP(MF);
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}
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/// canSimplifyCallFramePseudos - When possible, it's best to simplify the
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/// call frame pseudo ops before doing frame index elimination. This is
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/// possible only when frame index references between the pseudos won't
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/// need adjusting for the call frame adjustments. Normally, that's true
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/// if the function has a reserved call frame or a frame pointer. Some
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/// targets (Thumb2, for example) may have more complicated criteria,
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/// however, and can override this behavior.
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virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
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return hasReservedCallFrame(MF) || hasFP(MF);
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}
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// needsFrameIndexResolution - Do we need to perform FI resolution for
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// this function. Normally, this is required only when the function
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// has any stack objects. However, targets may want to override this.
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virtual bool needsFrameIndexResolution(const MachineFunction &MF) const;
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/// getFrameIndexReference - This method should return the base register
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/// and offset used to reference a frame index location. The offset is
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/// returned directly, and the base register is returned via FrameReg.
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virtual StackOffset getFrameIndexReference(const MachineFunction &MF, int FI,
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Register &FrameReg) const;
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/// Same as \c getFrameIndexReference, except that the stack pointer (as
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/// opposed to the frame pointer) will be the preferred value for \p
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/// FrameReg. This is generally used for emitting statepoint or EH tables that
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/// use offsets from RSP. If \p IgnoreSPUpdates is true, the returned
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/// offset is only guaranteed to be valid with respect to the value of SP at
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/// the end of the prologue.
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virtual StackOffset
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getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
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Register &FrameReg,
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bool IgnoreSPUpdates) const {
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// Always safe to dispatch to getFrameIndexReference.
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return getFrameIndexReference(MF, FI, FrameReg);
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}
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/// getNonLocalFrameIndexReference - This method returns the offset used to
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/// reference a frame index location. The offset can be from either FP/BP/SP
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/// based on which base register is returned by llvm.localaddress.
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virtual StackOffset getNonLocalFrameIndexReference(const MachineFunction &MF,
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int FI) const {
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// By default, dispatch to getFrameIndexReference. Interested targets can
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// override this.
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Register FrameReg;
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return getFrameIndexReference(MF, FI, FrameReg);
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}
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/// Returns the callee-saved registers as computed by determineCalleeSaves
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/// in the BitVector \p SavedRegs.
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virtual void getCalleeSaves(const MachineFunction &MF,
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BitVector &SavedRegs) const;
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/// This method determines which of the registers reported by
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/// TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.
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/// The default implementation checks populates the \p SavedRegs bitset with
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/// all registers which are modified in the function, targets may override
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/// this function to save additional registers.
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/// This method also sets up the register scavenger ensuring there is a free
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/// register or a frameindex available.
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/// This method should not be called by any passes outside of PEI, because
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/// it may change state passed in by \p MF and \p RS. The preferred
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/// interface outside PEI is getCalleeSaves.
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virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
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RegScavenger *RS = nullptr) const;
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/// processFunctionBeforeFrameFinalized - This method is called immediately
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/// before the specified function's frame layout (MF.getFrameInfo()) is
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/// finalized. Once the frame is finalized, MO_FrameIndex operands are
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/// replaced with direct constants. This method is optional.
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///
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virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF,
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RegScavenger *RS = nullptr) const {
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}
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/// processFunctionBeforeFrameIndicesReplaced - This method is called
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/// immediately before MO_FrameIndex operands are eliminated, but after the
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/// frame is finalized. This method is optional.
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virtual void
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|
|
processFunctionBeforeFrameIndicesReplaced(MachineFunction &MF,
|
||
|
|
RegScavenger *RS = nullptr) const {}
|
||
|
|
|
||
|
|
virtual unsigned getWinEHParentFrameOffset(const MachineFunction &MF) const {
|
||
|
|
report_fatal_error("WinEH not implemented for this target");
|
||
|
|
}
|
||
|
|
|
||
|
|
/// This method is called during prolog/epilog code insertion to eliminate
|
||
|
|
/// call frame setup and destroy pseudo instructions (but only if the Target
|
||
|
|
/// is using them). It is responsible for eliminating these instructions,
|
||
|
|
/// replacing them with concrete instructions. This method need only be
|
||
|
|
/// implemented if using call frame setup/destroy pseudo instructions.
|
||
|
|
/// Returns an iterator pointing to the instruction after the replaced one.
|
||
|
|
virtual MachineBasicBlock::iterator
|
||
|
|
eliminateCallFramePseudoInstr(MachineFunction &MF,
|
||
|
|
MachineBasicBlock &MBB,
|
||
|
|
MachineBasicBlock::iterator MI) const {
|
||
|
|
llvm_unreachable("Call Frame Pseudo Instructions do not exist on this "
|
||
|
|
"target!");
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
/// Order the symbols in the local stack frame.
|
||
|
|
/// The list of objects that we want to order is in \p objectsToAllocate as
|
||
|
|
/// indices into the MachineFrameInfo. The array can be reordered in any way
|
||
|
|
/// upon return. The contents of the array, however, may not be modified (i.e.
|
||
|
|
/// only their order may be changed).
|
||
|
|
/// By default, just maintain the original order.
|
||
|
|
virtual void
|
||
|
|
orderFrameObjects(const MachineFunction &MF,
|
||
|
|
SmallVectorImpl<int> &objectsToAllocate) const {
|
||
|
|
}
|
||
|
|
|
||
|
|
/// Check whether or not the given \p MBB can be used as a prologue
|
||
|
|
/// for the target.
|
||
|
|
/// The prologue will be inserted first in this basic block.
|
||
|
|
/// This method is used by the shrink-wrapping pass to decide if
|
||
|
|
/// \p MBB will be correctly handled by the target.
|
||
|
|
/// As soon as the target enable shrink-wrapping without overriding
|
||
|
|
/// this method, we assume that each basic block is a valid
|
||
|
|
/// prologue.
|
||
|
|
virtual bool canUseAsPrologue(const MachineBasicBlock &MBB) const {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
/// Check whether or not the given \p MBB can be used as a epilogue
|
||
|
|
/// for the target.
|
||
|
|
/// The epilogue will be inserted before the first terminator of that block.
|
||
|
|
/// This method is used by the shrink-wrapping pass to decide if
|
||
|
|
/// \p MBB will be correctly handled by the target.
|
||
|
|
/// As soon as the target enable shrink-wrapping without overriding
|
||
|
|
/// this method, we assume that each basic block is a valid
|
||
|
|
/// epilogue.
|
||
|
|
virtual bool canUseAsEpilogue(const MachineBasicBlock &MBB) const {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
/// Returns the StackID that scalable vectors should be associated with.
|
||
|
|
virtual TargetStackID::Value getStackIDForScalableVectors() const {
|
||
|
|
return TargetStackID::Default;
|
||
|
|
}
|
||
|
|
|
||
|
|
virtual bool isSupportedStackID(TargetStackID::Value ID) const {
|
||
|
|
switch (ID) {
|
||
|
|
default:
|
||
|
|
return false;
|
||
|
|
case TargetStackID::Default:
|
||
|
|
case TargetStackID::NoAlloc:
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/// Check if given function is safe for not having callee saved registers.
|
||
|
|
/// This is used when interprocedural register allocation is enabled.
|
||
|
|
static bool isSafeForNoCSROpt(const Function &F);
|
||
|
|
|
||
|
|
/// Check if the no-CSR optimisation is profitable for the given function.
|
||
|
|
virtual bool isProfitableForNoCSROpt(const Function &F) const {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
/// Return initial CFA offset value i.e. the one valid at the beginning of the
|
||
|
|
/// function (before any stack operations).
|
||
|
|
virtual int getInitialCFAOffset(const MachineFunction &MF) const;
|
||
|
|
|
||
|
|
/// Return initial CFA register value i.e. the one valid at the beginning of
|
||
|
|
/// the function (before any stack operations).
|
||
|
|
virtual Register getInitialCFARegister(const MachineFunction &MF) const;
|
||
|
|
|
||
|
|
/// Return the frame base information to be encoded in the DWARF subprogram
|
||
|
|
/// debug info.
|
||
|
|
virtual DwarfFrameBase getDwarfFrameBase(const MachineFunction &MF) const;
|
||
|
|
};
|
||
|
|
|
||
|
|
} // End llvm namespace
|
||
|
|
|
||
|
|
#endif
|