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Implement select.ll:test[3-6]

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12544 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-03-30 19:37:13 +00:00
parent 6d0996866c
commit c32b30a429
1 changed files with 32 additions and 4 deletions
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36
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1994,14 +1994,42 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
}
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (ConstantBool *C = dyn_cast<ConstantBool>(SI.getCondition()))
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
// select true, X, Y -> X
// select false, X, Y -> Y
if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
if (C == ConstantBool::True)
return ReplaceInstUsesWith(SI, SI.getTrueValue());
return ReplaceInstUsesWith(SI, TrueVal);
else {
assert(C == ConstantBool::False);
return ReplaceInstUsesWith(SI, SI.getFalseValue());
return ReplaceInstUsesWith(SI, FalseVal);
}
// select C, X, X -> X
if (TrueVal == FalseVal)
return ReplaceInstUsesWith(SI, TrueVal);
// Selecting between two constants?
if (Constant *TrueValC = dyn_cast<Constant>(TrueVal))
if (Constant *FalseValC = dyn_cast<Constant>(FalseVal)) {
if (SI.getType() == Type::BoolTy &&
isa<ConstantBool>(TrueValC) && isa<ConstantBool>(FalseValC)) {
// select C, true, false -> C
if (TrueValC == ConstantBool::True)
return ReplaceInstUsesWith(SI, CondVal);
// select C, false, true -> !C
return BinaryOperator::createNot(CondVal);
}
// If the true constant is a 1 and the false is a zero, turn this into a
// cast from bool.
if (FalseValC->isNullValue() && isa<ConstantInt>(TrueValC) &&
cast<ConstantInt>(TrueValC)->getRawValue() == 1)
return new CastInst(CondVal, SI.getType());
}
// Other transformations are possible!
return 0;
}