Fold ((1 << a) & 1) to (a == 0).
llvm-svn: 53276
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index 675f7ec..27af3c3 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/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)))
diff --git a/llvm/test/Transforms/InstCombine/2008-07-08-ShiftOneAndOne.ll b/llvm/test/Transforms/InstCombine/2008-07-08-ShiftOneAndOne.ll
new file mode 100644
index 0000000..956b9a6
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/2008-07-08-ShiftOneAndOne.ll
@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {icmp ne i32 \%a}
+; PR2330
+
+define i1 @foo(i32 %a) nounwind {
+entry:
+ %tmp15 = shl i32 1, %a ; <i32> [#uses=1]
+ %tmp237 = and i32 %tmp15, 1 ; <i32> [#uses=1]
+ %toBool = icmp eq i32 %tmp237, 0 ; <i1> [#uses=1]
+ ret i1 %toBool
+}