Instcombine this:

%shortcirc_val = select bool %tmp.1, bool true, bool %tmp.4             ; <bool> [#uses=1]
        %tmp.6 = cast bool %shortcirc_val to int                ; <int> [#uses=1]

into this:

        %shortcirc_val = or bool %tmp.1, %tmp.4         ; <bool> [#uses=1]
        %tmp.6 = cast bool %shortcirc_val to int                ; <int> [#uses=1]

not this:

        %tmp.4.cast = cast bool %tmp.4 to int           ; <int> [#uses=1]
        %tmp.6 = select bool %tmp.1, int 1, int %tmp.4.cast             ; <int> [#uses=1]

llvm-svn: 21389

llvm/lib/Transforms/Scalar/InstructionCombining.cpp

@@ -548,6 +548,9 @@ static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
   Value *FV = SI->getOperand(2);
 
   if (isa<Constant>(TV) || isa<Constant>(FV)) {
+    // Bool selects with constant operands can be folded to logical ops.
+    if (SI->getType() == Type::BoolTy) return 0;
+
     Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, IC);
     Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, IC);