[llvm-commits] [llvm] r131847 - in /llvm/trunk: lib/Transforms/Scalar/GVN.cpp test/Transforms/GVN/crash.ll

[Chris Lattner]

Author: lattner
Date: Sun May 22 02:03:34 2011
New Revision: 131847

URL: http://llvm.org/viewvc/llvm-project?rev=131847&view=rev
Log:
fix PR9841 by having GVN not process dead loads.  This was
causing it to get into infinite loops when it would widen a 
load (which can necessarily leave around dead loads).

Modified:
    llvm/trunk/lib/Transforms/Scalar/GVN.cpp
    llvm/trunk/test/Transforms/GVN/crash.ll

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=131847&r1=131846&r2=131847&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Sun May 22 02:03:34 2011
@@ -1607,6 +1607,11 @@
   if (L->isVolatile())
     return false;
 
+  if (L->use_empty()) {
+    markInstructionForDeletion(L);
+    return true;
+  }
+  
   // ... to a pointer that has been loaded from before...
   MemDepResult Dep = MD->getDependency(L);
 

Modified: llvm/trunk/test/Transforms/GVN/crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/crash.ll?rev=131847&r1=131846&r2=131847&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/GVN/crash.ll (original)
+++ llvm/trunk/test/Transforms/GVN/crash.ll Sun May 22 02:03:34 2011
@@ -151,3 +151,15 @@
 dead2:
   ret i32 %A
 }
+
+
+; PR9841
+define fastcc i8 @test5(i8* %P) nounwind {
+entry:
+  %0 = load i8* %P, align 2
+
+  %Q = getelementptr i8* %P, i32 1
+  %1 = load i8* %Q, align 1
+  ret i8 %1
+}
+