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Output a contorted sequence of instructions to make sure that we don't access 

off the bottom of the stack.  This fixes PR#41

llvm-svn: 9114
This commit is contained in:
Chris Lattner 2003-10-14 19:09:05 +00:00
parent 97c7a8ed1a
commit fdfe370406
1 changed files with 20 additions and 8 deletions
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28
llvm/lib/Target/X86/X86RegisterInfo.cpp
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@ -161,12 +161,24 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
int EBPOffset = MFI->getObjectOffset(MFI->getObjectIndexEnd()-1)+4;
if (NumBytes) { // adjust stack pointer: ESP -= numbytes
MI= BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
MBBI = MBB.insert(MBBI, MI)+1;
}
// Save EBP into the appropriate stack slot...
MI = addRegOffset(BuildMI(X86::MOVrm32, 5), // mov [ESP-<offset>], EBP
X86::ESP, EBPOffset).addReg(X86::EBP);
X86::ESP, EBPOffset+NumBytes).addReg(X86::EBP);
MBBI = MBB.insert(MBBI, MI)+1;
MI = BuildMI(X86::MOVrr32, 2, X86::EBP).addReg(X86::ESP);
// Update EBP with the new base value...
if (NumBytes == 0) // mov EBP, ESP
MI = BuildMI(X86::MOVrr32, 2, X86::EBP).addReg(X86::ESP);
else // lea EBP, [ESP+StackSize]
MI = addRegOffset(BuildMI(X86::LEAr32, 5, X86::EBP), X86::ESP, NumBytes);
MBBI = MBB.insert(MBBI, MI)+1;
} else {
// When we have no frame pointer, we reserve argument space for call sites
// in the function immediately on entry to the current function. This
@ -181,12 +193,12 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
// Update frame info to pretend that this is part of the stack...
MFI->setStackSize(NumBytes);
}
if (NumBytes) {
// adjust stack pointer: ESP -= numbytes
MI = BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
MBBI = 1+MBB.insert(MBBI, MI);
if (NumBytes) {
// adjust stack pointer: ESP -= numbytes
MI= BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
MBB.insert(MBBI, MI);
}
}
}