implement a TODO by teaching jump threading about "xor x, 1".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86739 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 36cc1fa..cbd8702 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -299,8 +299,20 @@
return !Result.empty();
}
- // TODO: Should handle the NOT form of XOR.
-
+ // Handle the NOT form of XOR.
+ if (I->getOpcode() == Instruction::Xor &&
+ isa<ConstantInt>(I->getOperand(1)) &&
+ cast<ConstantInt>(I->getOperand(1))->isOne()) {
+ ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result);
+ if (Result.empty())
+ return false;
+
+ // Invert the known values.
+ for (unsigned i = 0, e = Result.size(); i != e; ++i)
+ Result[i].first =
+ cast<ConstantInt>(ConstantExpr::getNot(Result[i].first));
+ return true;
+ }
}
// Handle compare with phi operand, where the PHI is defined in this block.