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Use MOV instead of LEA to restore ESP if callee-saved frame size is 0; if previous instruction updates esp, fold it in. 

llvm-svn: 40018
This commit is contained in:
Evan Cheng 2007-07-18 21:26:06 +00:00
parent 68659280fa
commit 8941071ae1
1 changed files with 20 additions and 14 deletions
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34
llvm/lib/Target/X86/X86RegisterInfo.cpp
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@ -1361,17 +1361,7 @@ void X86RegisterInfo::emitEpilogue(MachineFunction &MF,
--MBBI; --MBBI;
} }
// If dynamic alloca is used, then reset esp to point to the last if (NumBytes || MFI->hasVarSizedObjects()) {
// callee-saved slot before popping them off!
if (MFI->hasVarSizedObjects()) {
unsigned Opc = Is64Bit ? X86::LEA64r : X86::LEA32r;
MachineInstr *MI = addRegOffset(BuildMI(TII.get(Opc), StackPtr),
FramePtr, -CSSize);
MBB.insert(MBBI, MI);
NumBytes = 0;
}
if (NumBytes) { // adjust stack pointer back: ESP += numbytes
// If there is an ADD32ri or SUB32ri of ESP immediately before this // If there is an ADD32ri or SUB32ri of ESP immediately before this
// instruction, merge the two instructions. // instruction, merge the two instructions.
if (MBBI != MBB.begin()) { if (MBBI != MBB.begin()) {
@ -1389,11 +1379,27 @@ void X86RegisterInfo::emitEpilogue(MachineFunction &MF,
MBB.erase(PI); MBB.erase(PI);
} }
} }
if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, NumBytes, Is64Bit, TII);
} }
// If dynamic alloca is used, then reset esp to point to the last
// callee-saved slot before popping them off!
if (MFI->hasVarSizedObjects()) {
unsigned Opc = Is64Bit ? X86::LEA64r : X86::LEA32r;
if (CSSize) {
MachineInstr *MI = addRegOffset(BuildMI(TII.get(Opc), StackPtr),
FramePtr, -CSSize);
MBB.insert(MBBI, MI);
} else
BuildMI(MBB, MBBI, TII.get(Is64Bit ? X86::MOV64rr : X86::MOV32rr),StackPtr).
addReg(FramePtr);
NumBytes = 0;
}
// adjust stack pointer back: ESP += numbytes
if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, NumBytes, Is64Bit, TII);
// We're returning from function via eh_return. // We're returning from function via eh_return.
if (RetOpcode == X86::EH_RETURN) { if (RetOpcode == X86::EH_RETURN) {
MBBI = prior(MBB.end()); MBBI = prior(MBB.end());