Fold ((1 << a) & 1) to (a == 0).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53276 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 675f7ec..27af3c3 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3473,6 +3473,18 @@
}
break;
+
+ case Instruction::Shl:
+ case Instruction::LShr:
+ // (1 << x) & 1 --> zext(x == 0)
+ // (1 >> x) & 1 --> zext(x == 0)
+ if (AndRHSMask.getLimitedValue() == 1 && Op0LHS == AndRHS) {
+ Instruction *NewICmp = new ICmpInst(ICmpInst::ICMP_EQ, Op0RHS,
+ Constant::getNullValue(I.getType()));
+ InsertNewInstBefore(NewICmp, I);
+ return new ZExtInst(NewICmp, I.getType());
+ }
+ break;
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))