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Change the fp to integer code to not perform 2-byte stores followed by

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1 byte loads and other operations.  This is bad for store-forwarding on
common CPUs.  We now do this:

fnstcw WORD PTR [%ESP]
mov %AX, WORD PTR [%ESP]

instead of:

fnstcw WORD PTR [%ESP]
mov %AL, BYTE PTR [%ESP + 1]

llvm-svn: 22559
This commit is contained in:
Chris Lattner 2005-07-30 00:17:52 +00:00
parent 454caae5bd
commit a681fc64d6
1 changed files with 4 additions and 7 deletions
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11
lib/Target/X86/X86ISelPattern.cpp
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@ -4332,20 +4332,17 @@ void ISel::Select(SDOperand N) {
addFrameReference(BuildMI(BB, X86::FNSTCW16m, 4), CWFrameIdx);
// Load the old value of the high byte of the control word...
unsigned HighPartOfCW = MakeReg(MVT::i8);
addFrameReference(BuildMI(BB, X86::MOV8rm, 4, HighPartOfCW),
CWFrameIdx, 1);
unsigned OldCW = MakeReg(MVT::i16);
addFrameReference(BuildMI(BB, X86::MOV16rm, 4, OldCW), CWFrameIdx);
// Set the high part to be round to zero...
addFrameReference(BuildMI(BB, X86::MOV8mi, 5),
CWFrameIdx, 1).addImm(12);
addFrameReference(BuildMI(BB, X86::MOV16mi, 5), CWFrameIdx).addImm(0xB7F);
// Reload the modified control word now...
addFrameReference(BuildMI(BB, X86::FLDCW16m, 4), CWFrameIdx);
// Restore the memory image of control word to original value
addFrameReference(BuildMI(BB, X86::MOV8mr, 5),
CWFrameIdx, 1).addReg(HighPartOfCW);
addFrameReference(BuildMI(BB, X86::MOV16mr, 5), CWFrameIdx).addReg(OldCW);
// Get the X86 opcode to use.
switch (N.getOpcode()) {