Fix a representation change bug in the Hydrogen graph construction.

We could try to treat an HPhi as an HInstruction because the code did
not properly handle the case of a phi in a block with itself as one of
the predecessors.

BUG=v8:1134

Review URL: http://codereview.chromium.org/6471020

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6721 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -1813,17 +1813,15 @@ void HGraph::InsertRepresentationChangeForUse(HValue* value,
                                               bool is_truncating) {
   // Insert the representation change right before its use. For phi-uses we
   // insert at the end of the corresponding predecessor.
-  HBasicBlock* insert_block = use->block();
+  HInstruction* next = NULL;
   if (use->IsPhi()) {
     int index = 0;
     while (use->OperandAt(index) != value) ++index;
-    insert_block = insert_block->predecessors()->at(index);
+    next = use->block()->predecessors()->at(index)->end();
+  } else {
+    next = HInstruction::cast(use);
   }
 
-  HInstruction* next = (insert_block == use->block())
-      ? HInstruction::cast(use)
-      : insert_block->end();
-
   // For constants we try to make the representation change at compile
   // time. When a representation change is not possible without loss of
   // information we treat constants like normal instructions and insert the