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Fold prologue esp update when possible. 

llvm-svn: 39984
This commit is contained in:
Evan Cheng 2007-07-17 21:26:42 +00:00
parent 7c14110757
commit 97b5dc63d7
1 changed files with 22 additions and 1 deletions
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23
llvm/lib/Target/X86/X86RegisterInfo.cpp
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@ -1236,7 +1236,28 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
MBB.insert(MBBI, MI);
}
} else {
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
// If there is an ADD32ri or SUB32ri of ESP immediately after this
// instruction, merge the two instructions.
if (MBBI != MBB.end()) {
MachineBasicBlock::iterator NI = next(MBBI);
unsigned Opc = MBBI->getOpcode();
if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
Opc == X86::ADD32ri || Opc == X86::ADD32ri8) &&
MBBI->getOperand(0).getReg() == StackPtr) {
NumBytes -= MBBI->getOperand(2).getImm();
MBB.erase(MBBI);
MBBI = NI;
} else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
MBBI->getOperand(0).getReg() == StackPtr) {
NumBytes += MBBI->getOperand(2).getImm();
MBB.erase(MBBI);
MBBI = NI;
}
}
if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
}
}