246 lines
8.9 KiB
C++
246 lines
8.9 KiB
C++
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//===-- NVPTXPrologEpilogPass.cpp - NVPTX prolog/epilog inserter ----------===//
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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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// This file is a copy of the generic LLVM PrologEpilogInserter pass, modified
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// to remove unneeded functionality and to handle virtual registers. Most code
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// here is a copy of PrologEpilogInserter.cpp.
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//
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//===----------------------------------------------------------------------===//
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#include "NVPTX.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/TargetFrameLowering.h"
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#include "llvm/CodeGen/TargetRegisterInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DEBUG_TYPE "nvptx-prolog-epilog"
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namespace {
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class NVPTXPrologEpilogPass : public MachineFunctionPass {
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public:
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static char ID;
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NVPTXPrologEpilogPass() : MachineFunctionPass(ID) {}
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bool runOnMachineFunction(MachineFunction &MF) override;
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private:
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void calculateFrameObjectOffsets(MachineFunction &Fn);
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};
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}
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MachineFunctionPass *llvm::createNVPTXPrologEpilogPass() {
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return new NVPTXPrologEpilogPass();
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}
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char NVPTXPrologEpilogPass::ID = 0;
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bool NVPTXPrologEpilogPass::runOnMachineFunction(MachineFunction &MF) {
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const TargetSubtargetInfo &STI = MF.getSubtarget();
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const TargetFrameLowering &TFI = *STI.getFrameLowering();
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const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
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bool Modified = false;
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calculateFrameObjectOffsets(MF);
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for (MachineBasicBlock &MBB : MF) {
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for (MachineInstr &MI : MBB) {
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for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
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if (!MI.getOperand(i).isFI())
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continue;
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// Frame indices in debug values are encoded in a target independent
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// way with simply the frame index and offset rather than any
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// target-specific addressing mode.
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if (MI.isDebugValue()) {
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assert(i == 0 && "Frame indices can only appear as the first "
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"operand of a DBG_VALUE machine instruction");
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Register Reg;
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int64_t Offset =
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TFI.getFrameIndexReference(MF, MI.getOperand(0).getIndex(), Reg)
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.getFixed();
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MI.getOperand(0).ChangeToRegister(Reg, /*isDef=*/false);
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MI.getOperand(0).setIsDebug();
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auto *DIExpr = DIExpression::prepend(
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MI.getDebugExpression(), DIExpression::ApplyOffset, Offset);
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MI.getDebugExpressionOp().setMetadata(DIExpr);
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continue;
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}
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TRI.eliminateFrameIndex(MI, 0, i, nullptr);
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Modified = true;
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}
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}
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}
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// Add function prolog/epilog
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TFI.emitPrologue(MF, MF.front());
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
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// If last instruction is a return instruction, add an epilogue
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if (I->isReturnBlock())
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TFI.emitEpilogue(MF, *I);
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}
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return Modified;
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}
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/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
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static inline void AdjustStackOffset(MachineFrameInfo &MFI, int FrameIdx,
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bool StackGrowsDown, int64_t &Offset,
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Align &MaxAlign) {
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// If the stack grows down, add the object size to find the lowest address.
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if (StackGrowsDown)
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Offset += MFI.getObjectSize(FrameIdx);
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Align Alignment = MFI.getObjectAlign(FrameIdx);
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// If the alignment of this object is greater than that of the stack, then
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// increase the stack alignment to match.
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MaxAlign = std::max(MaxAlign, Alignment);
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// Adjust to alignment boundary.
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Offset = alignTo(Offset, Alignment);
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if (StackGrowsDown) {
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LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset
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<< "]\n");
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MFI.setObjectOffset(FrameIdx, -Offset); // Set the computed offset
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} else {
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LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset
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<< "]\n");
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MFI.setObjectOffset(FrameIdx, Offset);
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Offset += MFI.getObjectSize(FrameIdx);
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}
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}
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void
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NVPTXPrologEpilogPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
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const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
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const TargetRegisterInfo *RegInfo = Fn.getSubtarget().getRegisterInfo();
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bool StackGrowsDown =
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TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
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// Loop over all of the stack objects, assigning sequential addresses...
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MachineFrameInfo &MFI = Fn.getFrameInfo();
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// Start at the beginning of the local area.
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// The Offset is the distance from the stack top in the direction
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// of stack growth -- so it's always nonnegative.
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int LocalAreaOffset = TFI.getOffsetOfLocalArea();
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if (StackGrowsDown)
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LocalAreaOffset = -LocalAreaOffset;
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assert(LocalAreaOffset >= 0
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&& "Local area offset should be in direction of stack growth");
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int64_t Offset = LocalAreaOffset;
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// If there are fixed sized objects that are preallocated in the local area,
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// non-fixed objects can't be allocated right at the start of local area.
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// We currently don't support filling in holes in between fixed sized
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// objects, so we adjust 'Offset' to point to the end of last fixed sized
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// preallocated object.
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for (int i = MFI.getObjectIndexBegin(); i != 0; ++i) {
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int64_t FixedOff;
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if (StackGrowsDown) {
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// The maximum distance from the stack pointer is at lower address of
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// the object -- which is given by offset. For down growing stack
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// the offset is negative, so we negate the offset to get the distance.
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FixedOff = -MFI.getObjectOffset(i);
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} else {
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// The maximum distance from the start pointer is at the upper
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// address of the object.
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FixedOff = MFI.getObjectOffset(i) + MFI.getObjectSize(i);
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}
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if (FixedOff > Offset) Offset = FixedOff;
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}
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// NOTE: We do not have a call stack
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Align MaxAlign = MFI.getMaxAlign();
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// No scavenger
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// FIXME: Once this is working, then enable flag will change to a target
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// check for whether the frame is large enough to want to use virtual
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// frame index registers. Functions which don't want/need this optimization
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// will continue to use the existing code path.
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if (MFI.getUseLocalStackAllocationBlock()) {
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Align Alignment = MFI.getLocalFrameMaxAlign();
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// Adjust to alignment boundary.
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Offset = alignTo(Offset, Alignment);
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LLVM_DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
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// Resolve offsets for objects in the local block.
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for (unsigned i = 0, e = MFI.getLocalFrameObjectCount(); i != e; ++i) {
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std::pair<int, int64_t> Entry = MFI.getLocalFrameObjectMap(i);
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int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
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LLVM_DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" << FIOffset
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<< "]\n");
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MFI.setObjectOffset(Entry.first, FIOffset);
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}
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// Allocate the local block
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Offset += MFI.getLocalFrameSize();
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MaxAlign = std::max(Alignment, MaxAlign);
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}
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// No stack protector
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// Then assign frame offsets to stack objects that are not used to spill
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// callee saved registers.
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for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
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if (MFI.isObjectPreAllocated(i) &&
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MFI.getUseLocalStackAllocationBlock())
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continue;
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if (MFI.isDeadObjectIndex(i))
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continue;
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AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
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}
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// No scavenger
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if (!TFI.targetHandlesStackFrameRounding()) {
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// If we have reserved argument space for call sites in the function
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// immediately on entry to the current function, count it as part of the
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// overall stack size.
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if (MFI.adjustsStack() && TFI.hasReservedCallFrame(Fn))
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Offset += MFI.getMaxCallFrameSize();
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// Round up the size to a multiple of the alignment. If the function has
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// any calls or alloca's, align to the target's StackAlignment value to
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// ensure that the callee's frame or the alloca data is suitably aligned;
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// otherwise, for leaf functions, align to the TransientStackAlignment
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// value.
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Align StackAlign;
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if (MFI.adjustsStack() || MFI.hasVarSizedObjects() ||
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(RegInfo->needsStackRealignment(Fn) && MFI.getObjectIndexEnd() != 0))
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StackAlign = TFI.getStackAlign();
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else
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StackAlign = TFI.getTransientStackAlign();
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// If the frame pointer is eliminated, all frame offsets will be relative to
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// SP not FP. Align to MaxAlign so this works.
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Offset = alignTo(Offset, std::max(StackAlign, MaxAlign));
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}
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// Update frame info to pretend that this is part of the stack...
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int64_t StackSize = Offset - LocalAreaOffset;
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MFI.setStackSize(StackSize);
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}
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