release/19.x: [InstCombine] Handle constant GEP expr in SimplifyDemandedUseBits (#116794)

[llvmbot]

Backport 03d8831

Requested by: @dtcxzyw

[llvmbot]

@nikic What do you think about merging this PR to the release branch?

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@llvm/pr-subscribers-llvm-transforms

Author: None (llvmbot)

Changes

Backport 03d8831

Requested by: @dtcxzyw

---

Full diff: https://github.com/llvm/llvm-project/pull/116814.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp (+1-1)
• (modified) llvm/test/Transforms/InstCombine/ptrmask.ll (+13)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 8a6ec3076ac621..b9d06b59368508 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1004,7 +1004,7 @@ Value *InstCombinerImpl::SimplifyDemandedUseBits(Instruction *I,
             uint64_t MaskedGEPIndex = HighBitsGEPIndex | MaskedLowBitsGEPIndex;
 
             if (MaskedGEPIndex != GEPIndex) {
-              auto *GEP = cast<GetElementPtrInst>(II->getArgOperand(0));
+              auto *GEP = cast<GEPOperator>(II->getArgOperand(0));
               Builder.SetInsertPoint(I);
               Type *GEPIndexType =
                   DL.getIndexType(GEP->getPointerOperand()->getType());
diff --git a/llvm/test/Transforms/InstCombine/ptrmask.ll b/llvm/test/Transforms/InstCombine/ptrmask.ll
index 4631b81cd1ce1f..cd998bac3f9f0d 100644
--- a/llvm/test/Transforms/InstCombine/ptrmask.ll
+++ b/llvm/test/Transforms/InstCombine/ptrmask.ll
@@ -578,3 +578,16 @@ define ptr @ptrmask_is_useless_fail1(i64 %i, i64 %m) {
   %r = call ptr @llvm.ptrmask.p0.i64(ptr %p0, i64 %m0)
   ret ptr %r
 }
+
+@GC_arrays = external global { i8, i8, i64 }
+
+define ptr @ptrmask_demandedbits_constantexpr() {
+; CHECK-LABEL: define ptr @ptrmask_demandedbits_constantexpr() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ALIGNED_RESULT:%.*]] = call align 8 ptr @llvm.ptrmask.p0.i64(ptr nonnull @GC_arrays, i64 -8)
+; CHECK-NEXT:    ret ptr [[ALIGNED_RESULT]]
+;
+entry:
+  %aligned_result = call ptr @llvm.ptrmask.p0.i64(ptr getelementptr inbounds (i8, ptr @GC_arrays, i64 1), i64 -8)
+  ret ptr %aligned_result
+}

[dtcxzyw]

@tstellar We should disable the greeter for PRs created by llvmbot.

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@dtcxzyw (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.