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//===-- MachineFrameInfo.cpp ---------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
/// \file Implements MachineFrameInfo that manages the stack frame.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#define DEBUG_TYPE "codegen"
using namespace llvm;
void MachineFrameInfo::ensureMaxAlignment(Align Alignment) {
if (!StackRealignable)
assert(Alignment <= StackAlignment &&
"For targets without stack realignment, Alignment is out of limit!");
if (MaxAlignment < Alignment)
MaxAlignment = Alignment;
}
/// Clamp the alignment if requested and emit a warning.
static inline Align clampStackAlignment(bool ShouldClamp, Align Alignment,
Align StackAlignment) {
if (!ShouldClamp || Alignment <= StackAlignment)
return Alignment;
LLVM_DEBUG(dbgs() << "Warning: requested alignment " << DebugStr(Alignment)
<< " exceeds the stack alignment "
<< DebugStr(StackAlignment)
<< " when stack realignment is off" << '\n');
return StackAlignment;
}
int MachineFrameInfo::CreateStackObject(uint64_t Size, Align Alignment,
bool IsSpillSlot,
const AllocaInst *Alloca,
uint8_t StackID) {
assert(Size != 0 && "Cannot allocate zero size stack objects!");
Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
Objects.push_back(StackObject(Size, Alignment, 0, false, IsSpillSlot, Alloca,
!IsSpillSlot, StackID));
int Index = (int)Objects.size() - NumFixedObjects - 1;
assert(Index >= 0 && "Bad frame index!");
if (contributesToMaxAlignment(StackID))
ensureMaxAlignment(Alignment);
return Index;
}
int MachineFrameInfo::CreateSpillStackObject(uint64_t Size, Align Alignment) {
Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
CreateStackObject(Size, Alignment, true);
int Index = (int)Objects.size() - NumFixedObjects - 1;
ensureMaxAlignment(Alignment);
return Index;
}
int MachineFrameInfo::CreateVariableSizedObject(Align Alignment,
const AllocaInst *Alloca) {
HasVarSizedObjects = true;
Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca, true));
ensureMaxAlignment(Alignment);
return (int)Objects.size()-NumFixedObjects-1;
}
int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
bool IsImmutable, bool IsAliased) {
assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
// The alignment of the frame index can be determined from its offset from
// the incoming frame position. If the frame object is at offset 32 and
// the stack is guaranteed to be 16-byte aligned, then we know that the
// object is 16-byte aligned. Note that unlike the non-fixed case, if the
// stack needs realignment, we can't assume that the stack will in fact be
// aligned.
Align Alignment =
commonAlignment(ForcedRealign ? Align(1) : StackAlignment, SPOffset);
Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
Objects.insert(Objects.begin(),
StackObject(Size, Alignment, SPOffset, IsImmutable,
/*IsSpillSlot=*/false, /*Alloca=*/nullptr,
IsAliased));
return -++NumFixedObjects;
}
int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size,
int64_t SPOffset,
bool IsImmutable) {
Align Alignment =
commonAlignment(ForcedRealign ? Align(1) : StackAlignment, SPOffset);
Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
Objects.insert(Objects.begin(),
StackObject(Size, Alignment, SPOffset, IsImmutable,
/*IsSpillSlot=*/true, /*Alloca=*/nullptr,
/*IsAliased=*/false));
return -++NumFixedObjects;
}
BitVector MachineFrameInfo::getPristineRegs(const MachineFunction &MF) const {
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
BitVector BV(TRI->getNumRegs());
// Before CSI is calculated, no registers are considered pristine. They can be
// freely used and PEI will make sure they are saved.
if (!isCalleeSavedInfoValid())
return BV;
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR;
++CSR)
BV.set(*CSR);
// Saved CSRs are not pristine.
for (const auto &I : getCalleeSavedInfo())
for (MCSubRegIterator S(I.getReg(), TRI, true); S.isValid(); ++S)
BV.reset(*S);
return BV;
}
uint64_t MachineFrameInfo::estimateStackSize(const MachineFunction &MF) const {
const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
Align MaxAlign = getMaxAlign();
int64_t Offset = 0;
// This code is very, very similar to PEI::calculateFrameObjectOffsets().
// It really should be refactored to share code. Until then, changes
// should keep in mind that there's tight coupling between the two.
for (int i = getObjectIndexBegin(); i != 0; ++i) {
// Only estimate stack size of default stack.
if (getStackID(i) != TargetStackID::Default)
continue;
int64_t FixedOff = -getObjectOffset(i);
if (FixedOff > Offset) Offset = FixedOff;
}
for (unsigned i = 0, e = getObjectIndexEnd(); i != e; ++i) {
// Only estimate stack size of live objects on default stack.
if (isDeadObjectIndex(i) || getStackID(i) != TargetStackID::Default)
continue;
Offset += getObjectSize(i);
Align Alignment = getObjectAlign(i);
// Adjust to alignment boundary
Offset = alignTo(Offset, Alignment);
MaxAlign = std::max(Alignment, MaxAlign);
}
if (adjustsStack() && TFI->hasReservedCallFrame(MF))
Offset += getMaxCallFrameSize();
// Round up the size to a multiple of the alignment. If the function has
// any calls or alloca's, align to the target's StackAlignment value to
// ensure that the callee's frame or the alloca data is suitably aligned;
// otherwise, for leaf functions, align to the TransientStackAlignment
// value.
Align StackAlign;
if (adjustsStack() || hasVarSizedObjects() ||
(RegInfo->hasStackRealignment(MF) && getObjectIndexEnd() != 0))
StackAlign = TFI->getStackAlign();
else
StackAlign = TFI->getTransientStackAlign();
// If the frame pointer is eliminated, all frame offsets will be relative to
// SP not FP. Align to MaxAlign so this works.
StackAlign = std::max(StackAlign, MaxAlign);
return alignTo(Offset, StackAlign);
}
void MachineFrameInfo::computeMaxCallFrameSize(const MachineFunction &MF) {
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u &&
"Can only compute MaxCallFrameSize if Setup/Destroy opcode are known");
MaxCallFrameSize = 0;
for (const MachineBasicBlock &MBB : MF) {
for (const MachineInstr &MI : MBB) {
unsigned Opcode = MI.getOpcode();
if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) {
unsigned Size = TII.getFrameSize(MI);
MaxCallFrameSize = std::max(MaxCallFrameSize, Size);
AdjustsStack = true;
} else if (MI.isInlineAsm()) {
// Some inline asm's need a stack frame, as indicated by operand 1.
unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
AdjustsStack = true;
}
}
}
}
void MachineFrameInfo::print(const MachineFunction &MF, raw_ostream &OS) const{
if (Objects.empty()) return;
const TargetFrameLowering *FI = MF.getSubtarget().getFrameLowering();
int ValOffset = (FI ? FI->getOffsetOfLocalArea() : 0);
OS << "Frame Objects:\n";
for (unsigned i = 0, e = Objects.size(); i != e; ++i) {
const StackObject &SO = Objects[i];
OS << " fi#" << (int)(i-NumFixedObjects) << ": ";
if (SO.StackID != 0)
OS << "id=" << static_cast<unsigned>(SO.StackID) << ' ';
if (SO.Size == ~0ULL) {
OS << "dead\n";
continue;
}
if (SO.Size == 0)
OS << "variable sized";
else
OS << "size=" << SO.Size;
OS << ", align=" << SO.Alignment.value();
if (i < NumFixedObjects)
OS << ", fixed";
if (i < NumFixedObjects || SO.SPOffset != -1) {
int64_t Off = SO.SPOffset - ValOffset;
OS << ", at location [SP";
if (Off > 0)
OS << "+" << Off;
else if (Off < 0)
OS << Off;
OS << "]";
}
OS << "\n";
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void MachineFrameInfo::dump(const MachineFunction &MF) const {
print(MF, dbgs());
}
#endif