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Implement InstCombine/select.ll:test13* 

llvm-svn: 12821
This commit is contained in:
Chris Lattner 2004-04-10 22:21:27 +00:00
parent 1f99df6d27
commit 623fba1107
1 changed files with 22 additions and 0 deletions
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22
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2209,6 +2209,28 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return new CastInst(NotCond, SI.getType());
}
}
// See if we are selecting two values based on a comparison of the two values.
if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
// Transform (X == Y) ? X : Y -> Y
if (SCI->getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(SI, FalseVal);
// Transform (X != Y) ? X : Y -> X
if (SCI->getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SI, TrueVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
} else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
// Transform (X == Y) ? Y : X -> X
if (SCI->getOpcode() == Instruction::SetEQ)
return ReplaceInstUsesWith(SI, TrueVal);
// Transform (X != Y) ? Y : X -> Y
if (SCI->getOpcode() == Instruction::SetNE)
return ReplaceInstUsesWith(SI, FalseVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
}
}
// See if we can fold the select into one of our operands.
if (SI.getType()->isInteger()) {