diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp --- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp +++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp @@ -1932,7 +1932,7 @@ // If all preds provide undef, just nuke the xor, because it is undef too. BO->replaceAllUsesWith(UndefValue::get(BO->getType())); BO->eraseFromParent(); - } else if (SplitVal->isZero()) { + } else if (SplitVal->isZero() && BO != BO->getOperand(isLHS)) { // If all preds provide 0, replace the xor with the other input. BO->replaceAllUsesWith(BO->getOperand(isLHS)); BO->eraseFromParent(); diff --git a/llvm/test/Transforms/JumpThreading/phi-xor-branch.ll b/llvm/test/Transforms/JumpThreading/phi-xor-branch.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/JumpThreading/phi-xor-branch.ll @@ -0,0 +1,33 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -S -passes=jump-threading %s | FileCheck %s + +; https://github.com/llvm/llvm-project/issues/58812 + +define void @test() { +; CHECK-LABEL: @test( +; CHECK-NEXT: entry: +; CHECK-NEXT: br label [[EXIT:%.*]] +; CHECK: loop: +; CHECK-NEXT: [[DUMMY:%.*]] = phi i16 [ 0, [[LOOP:%.*]] ] +; CHECK-NEXT: [[CMP:%.*]] = icmp eq i16 0, 1 +; CHECK-NEXT: [[XOR:%.*]] = xor i1 false, [[XOR]] +; CHECK-NEXT: br i1 [[XOR]], label [[LOOP]], label [[EXIT]] +; CHECK: exit: +; CHECK-NEXT: ret void +; +entry: + br i1 false, label %loop, label %exit + +loop: + %bool = phi i1 [ %xor, %loop.latch ], [ false, %entry ] + %cmp = icmp eq i16 0, 1 + %xor = xor i1 %cmp, %bool + br i1 %bool, label %loop.latch, label %exit + +loop.latch: + %dummy = phi i16 [ 0, %loop ] + br label %loop + +exit: + ret void +}