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Make comparisons against the null pointer as efficient as integer comparisons 

against zero.  In particular, don't emit:

        mov %ESI, 0
        cmp %ECX, %ESI

instead, emit:

       test %ECX, %ECX

llvm-svn: 13407
This commit is contained in:
Chris Lattner 2004-05-07 19:55:55 +00:00
parent cf5822a2be
commit cecf3f94a4
1 changed files with 8 additions and 1 deletions
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9
llvm/lib/Target/X86/InstSelectSimple.cpp
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@ -829,7 +829,14 @@ unsigned ISel::EmitComparison(unsigned OpNum, Value *Op0, Value *Op1,
unsigned Op0r = getReg(Op0, MBB, IP); unsigned Op0r = getReg(Op0, MBB, IP);
// Special case handling of: cmp R, i // Special case handling of: cmp R, i
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { if (isa<ConstantPointerNull>(Op1)) {
if (OpNum < 2) // seteq/setne -> test
BuildMI(*MBB, IP, X86::TEST32rr, 2).addReg(Op0r).addReg(Op0r);
else
BuildMI(*MBB, IP, X86::CMP32ri, 2).addReg(Op0r).addImm(0);
return OpNum;
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Class == cByte || Class == cShort || Class == cInt) { if (Class == cByte || Class == cShort || Class == cInt) {
unsigned Op1v = CI->getRawValue(); unsigned Op1v = CI->getRawValue();