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Try to not emit the dead side of ?: if the condition is a constant. 

llvm-svn: 59061
This commit is contained in:
Chris Lattner 2008-11-11 18:56:45 +00:00
parent c3b41e31fb
commit d53e23328e
1 changed files with 21 additions and 4 deletions
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25
clang/lib/CodeGen/CGExprScalar.cpp
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@ -1110,14 +1110,31 @@ Value *ScalarExprEmitter::VisitBinComma(const BinaryOperator *E) {
Value *ScalarExprEmitter:: Value *ScalarExprEmitter::
VisitConditionalOperator(const ConditionalOperator *E) { VisitConditionalOperator(const ConditionalOperator *E) {
llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.?");
llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.:");
llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.cont");
// Evaluate the conditional, then convert it to bool. We do this explicitly // Evaluate the conditional, then convert it to bool. We do this explicitly
// because we need the unconverted value if this is a GNU ?: expression with // because we need the unconverted value if this is a GNU ?: expression with
// missing middle value. // missing middle value.
Value *CondVal = CGF.EmitScalarExpr(E->getCond()); Value *CondVal = CGF.EmitScalarExpr(E->getCond());
// If the condition folded to a constant, try to elide the dead side. We
// can't do this if the dead side contains a label.
if (llvm::ConstantInt *CondCI = dyn_cast<llvm::ConstantInt>(CondVal)) {
Expr *Live = E->getLHS(), *Dead = E->getRHS();
if (CondCI->getZExtValue() == 0)
std::swap(Live, Dead);
if (!Dead || !CGF.ContainsLabel(Dead)) {
// Emit the live side.
if (Live)
return Visit(Live);
// Perform promotions, to handle cases like "short ?: int"
return EmitScalarConversion(CondVal, E->getCond()->getType(),
E->getType());
}
}
llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.?");
llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.:");
llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.cont");
Value *CondBoolVal =CGF.EmitScalarConversion(CondVal, E->getCond()->getType(), Value *CondBoolVal =CGF.EmitScalarConversion(CondVal, E->getCond()->getType(),
CGF.getContext().BoolTy); CGF.getContext().BoolTy);
Builder.CreateCondBr(CondBoolVal, LHSBlock, RHSBlock); Builder.CreateCondBr(CondBoolVal, LHSBlock, RHSBlock);