[PATCH] D47825: [Mem2Reg] Avoid replacing load with itself in promoteSingleBlockAlloca.

[Florian Hahn via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL334187: [Mem2Reg] Avoid replacing load with itself in promoteSingleBlockAlloca. (authored by fhahn, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D47825?vs=150131&id=150293#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D47825

Files:
  llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
  llvm/trunk/test/Transforms/Mem2Reg/pr37632-unreachable-list-of-stores.ll


Index: llvm/trunk/test/Transforms/Mem2Reg/pr37632-unreachable-list-of-stores.ll
===================================================================
--- llvm/trunk/test/Transforms/Mem2Reg/pr37632-unreachable-list-of-stores.ll
+++ llvm/trunk/test/Transforms/Mem2Reg/pr37632-unreachable-list-of-stores.ll
@@ -0,0 +1,20 @@
+; RUN: opt -mem2reg < %s -S | FileCheck %s
+
+
+; CHECK-LABEL: void @patatino()
+; CHECK-NEXT: ret void
+
+; CHECK-LABEL: cantreachme:
+; CHECK-NEXT: %dec = add nsw i32 undef, -1
+; CHECK-NEXT: br label %cantreachme
+
+define void @patatino() {
+  %a = alloca i32, align 4
+  ret void
+cantreachme:
+  %dec = add nsw i32 %tmp, -1
+  store i32 %dec, i32* %a
+  store i32 %tmp, i32* %a
+  %tmp = load i32, i32* %a
+  br label %cantreachme
+}
Index: llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -511,6 +511,11 @@
           !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
         addAssumeNonNull(AC, LI);
 
+      // If the replacement value is the load, this must occur in unreachable
+      // code.
+      if (ReplVal == LI)
+        ReplVal = UndefValue::get(LI->getType());
+
       LI->replaceAllUsesWith(ReplVal);
     }
 


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