Try to not emit the dead side of ?: if the condition is a constant.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59061 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 82f0cc7..bf22902 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1110,14 +1110,31 @@
Value *ScalarExprEmitter::
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
// because we need the unconverted value if this is a GNU ?: expression with
// missing middle value.
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(),
CGF.getContext().BoolTy);
Builder.CreateCondBr(CondBoolVal, LHSBlock, RHSBlock);