[llvm] r207302 - RecursivelyDeleteTriviallyDeadInstructions() could remove

[Gerolf Hoflehner]

Author: ghoflehner
Date: Fri Apr 25 20:19:16 2014
New Revision: 207302

URL: http://llvm.org/viewvc/llvm-project?rev=207302&view=rev
Log:
RecursivelyDeleteTriviallyDeadInstructions() could remove
more than 1 instruction. The caller need to be aware of this
and adjust instruction iterators accordingly.

rdar://16679376


Added:
    llvm/trunk/test/Transforms/InstSimplify/dead-code-removal.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
    llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp?rev=207302&r1=207301&r2=207302&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp Fri Apr 25 20:19:16 2014
@@ -127,7 +127,15 @@ bool LoopInstSimplify::runOnLoop(Loop *L
             ++NumSimplified;
           }
         }
-        LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
+        bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
+        if (res) {
+          // RecursivelyDeleteTriviallyDeadInstruction can remove
+          // more than one instruction, so simply incrementing the
+          // iterator does not work. When instructions get deleted
+          // re-iterate instead.
+          BI = BB->begin(); BE = BB->end();
+          LocalChanged |= res;
+        }
 
         if (IsSubloopHeader && !isa<PHINode>(I))
           break;

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp?rev=207302&r1=207301&r2=207302&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp Fri Apr 25 20:19:16 2014
@@ -76,7 +76,15 @@ namespace {
                 ++NumSimplified;
                 Changed = true;
               }
-            Changed |= RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
+            bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
+            if (res)  {
+              // RecursivelyDeleteTriviallyDeadInstruction can remove
+              // more than one instruction, so simply incrementing the
+              // iterator does not work. When instructions get deleted
+              // re-iterate instead.
+              BI = BB->begin(); BE = BB->end();
+              Changed |= res;
+            }
           }
 
         // Place the list of instructions to simplify on the next loop iteration

Added: llvm/trunk/test/Transforms/InstSimplify/dead-code-removal.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/dead-code-removal.ll?rev=207302&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/dead-code-removal.ll (added)
+++ llvm/trunk/test/Transforms/InstSimplify/dead-code-removal.ll Fri Apr 25 20:19:16 2014
@@ -0,0 +1,15 @@
+; RUN: opts -instsimplify -S < %s | FileCheck %s
+
+define void @foo() nounwind {
+  br i1 undef, label %1, label %4
+
+; <label>:1                                       ; preds = %1, %0
+; CHECK-NOT: phi
+; CHECK-NOT: sub
+  %2 = phi i32 [ %3, %1 ], [ undef, %0 ]
+  %3 = sub i32 0, undef
+  br label %1
+
+; <label>:4                                       ; preds = %0
+  ret void
+}