[PATCH] D74278: [InstCombine] Fix infinite loop in min/max load/store bitcast combine (PR44835)

[Nikita Popov via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG23db9724d0e5: [InstCombine] Fix infinite loop in min/max load/store bitcast combine (PR44835) (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74278/new/

https://reviews.llvm.org/D74278

Files:
  llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/test/Transforms/InstCombine/pr44835.ll


Index: llvm/test/Transforms/InstCombine/pr44835.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/pr44835.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+; This test used to cause an infinite loop in the load/store min/max bitcast
+; transform.
+
+define void @test(i32* %p, i32* %p2) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:    [[V:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[V2:%.*]] = load i32, i32* [[P2:%.*]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[V2]], [[V]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[CMP]], i32 [[V2]], i32 [[V]]
+; CHECK-NEXT:    store i32 [[TMP1]], i32* [[P]], align 4
+; CHECK-NEXT:    ret void
+;
+  %v = load i32, i32* %p, align 4
+  %v2 = load i32, i32* %p2, align 4
+  %cmp = icmp ult i32 %v2, %v
+  %sel = select i1 %cmp, i32* %p2, i32* %p
+  %p8 = bitcast i32* %p to i8*
+  %sel8 = bitcast i32* %sel to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %p8, i8* align 4 %sel8, i64 4, i1 false)
+  ret void
+}
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0
+
+attributes #0 = { argmemonly nounwind willreturn }
Index: llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -1320,6 +1320,11 @@
   if (!isMinMaxWithLoads(LoadAddr, CmpLoadTy))
     return false;
 
+  // Make sure the type would actually change.
+  // This condition can be hit with chains of bitcasts.
+  if (LI->getType() == CmpLoadTy)
+    return false;
+
   // Make sure we're not changing the size of the load/store.
   const auto &DL = IC.getDataLayout();
   if (DL.getTypeStoreSizeInBits(LI->getType()) !=


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