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Force use of a frame-pointer if there is anything on the stack that is aligned 

more than the OS keeps the stack aligned.

llvm-svn: 27381
This commit is contained in:
Chris Lattner 2006-04-03 22:03:29 +00:00
parent b710a81e54
commit 5400727595
1 changed files with 18 additions and 7 deletions
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25
llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
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@ -196,8 +196,16 @@ MachineInstr *PPCRegisterInfo::foldMemoryOperand(MachineInstr *MI,
// pointer register. This is true if the function has variable sized allocas or // pointer register. This is true if the function has variable sized allocas or
// if frame pointer elimination is disabled. // if frame pointer elimination is disabled.
// //
static bool hasFP(MachineFunction &MF) { static bool hasFP(const MachineFunction &MF) {
return NoFramePointerElim || MF.getFrameInfo()->hasVarSizedObjects(); const MachineFrameInfo *MFI = MF.getFrameInfo();
unsigned TargetAlign = MF.getTarget().getFrameInfo()->getStackAlignment();
// If frame pointers are forced, if there are variable sized stack objects,
// or if there is an object on the stack that requires more alignment than is
// normally provided, use a frame pointer.
//
return NoFramePointerElim || MFI->hasVarSizedObjects() ||
MFI->getMaxAlignment() > TargetAlign;
} }
void PPCRegisterInfo:: void PPCRegisterInfo::
@ -331,9 +339,12 @@ void PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
MachineBasicBlock::iterator MBBI = MBB.begin(); MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo(); MachineFrameInfo *MFI = MF.getFrameInfo();
// Do we have a frame pointer for this function?
bool HasFP = hasFP(MF);
// Scan the first few instructions of the prolog, looking for an UPDATE_VRSAVE // Scan the prolog, looking for an UPDATE_VRSAVE instruction. If we find it,
// instruction. If we find it, process it. // process it.
for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) { for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) {
if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) { if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) {
HandleVRSaveUpdate(MBBI, MF.getUsedPhysregs()); HandleVRSaveUpdate(MBBI, MF.getUsedPhysregs());
@ -364,7 +375,7 @@ void PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
// If we are a leaf function, and use up to 224 bytes of stack space, // If we are a leaf function, and use up to 224 bytes of stack space,
// and don't have a frame pointer, then we do not need to adjust the stack // and don't have a frame pointer, then we do not need to adjust the stack
// pointer (we fit in the Red Zone). // pointer (we fit in the Red Zone).
if ((NumBytes == 0) || (NumBytes <= 224 && !hasFP(MF) && !MFI->hasCalls() && if ((NumBytes == 0) || (NumBytes <= 224 && !HasFP && !MFI->hasCalls() &&
MaxAlign <= TargetAlign)) { MaxAlign <= TargetAlign)) {
MFI->setStackSize(0); MFI->setStackSize(0);
return; return;
@ -374,7 +385,7 @@ void PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
// of the stack and round the size to a multiple of the alignment. // of the stack and round the size to a multiple of the alignment.
unsigned Align = std::max(TargetAlign, MaxAlign); unsigned Align = std::max(TargetAlign, MaxAlign);
unsigned GPRSize = 4; unsigned GPRSize = 4;
unsigned Size = hasFP(MF) ? GPRSize + GPRSize : GPRSize; unsigned Size = HasFP ? GPRSize + GPRSize : GPRSize;
NumBytes = (NumBytes+Size+Align-1)/Align*Align; NumBytes = (NumBytes+Size+Align-1)/Align*Align;
// Update frame info to pretend that this is part of the stack... // Update frame info to pretend that this is part of the stack...
@ -407,7 +418,7 @@ void PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
} }
// If there is a frame pointer, copy R1 (SP) into R31 (FP) // If there is a frame pointer, copy R1 (SP) into R31 (FP)
if (hasFP(MF)) { if (HasFP) {
BuildMI(MBB, MBBI, PPC::STW, 3) BuildMI(MBB, MBBI, PPC::STW, 3)
.addReg(PPC::R31).addSImm(GPRSize).addReg(PPC::R1); .addReg(PPC::R31).addSImm(GPRSize).addReg(PPC::R1);
BuildMI(MBB, MBBI, PPC::OR4, 2, PPC::R31).addReg(PPC::R1).addReg(PPC::R1); BuildMI(MBB, MBBI, PPC::OR4, 2, PPC::R31).addReg(PPC::R1).addReg(PPC::R1);