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

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: chandlerc, davide, efriedma.

We do the same thing in rewriteSingleStoreAlloca.

Fixes PR37632.


https://reviews.llvm.org/D47825

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


Index: test/Transforms/Mem2Reg/pr37632-unreachable-list-of-stores.ll
===================================================================
--- /dev/null
+++ 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: lib/Transforms/Utils/PromoteMemoryToRegister.cpp
===================================================================
--- lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ 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);
     }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D47825.150131.patch
Type: text/x-patch
Size: 1243 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180606/cbd65e53/attachment.bin>