vendor/llvm-project/llvmorg-18.1.0-rc2-0-gc6c86965d967

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index a8a5f9831e15..79873a9b4cbb 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -802,6 +802,9 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
         return InsertNewInstWith(LShr, I->getIterator());
       } else if (Known.One[BitWidth-ShiftAmt-1]) { // New bits are known one.
         Known.One |= HighBits;
+        // SignBits may be out-of-sync with Known.countMinSignBits(). Mask out
+        // high bits of Known.Zero to avoid conflicts.
+        Known.Zero &= ~HighBits;
       }
     } else {
       computeKnownBits(I, Known, Depth, CxtI);