Fix a deoptimization bug.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 5fc56462bb02dbdc6944c6c981f666d88484aa01..3f0cb0cd228812a0611af22caf143e4852ec5901 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -706,7 +706,9 @@ LInstruction* LChunkBuilder::DefineFixedDouble(
 
 LInstruction* LChunkBuilder::AssignEnvironment(LInstruction* instr) {
   HEnvironment* hydrogen_env = current_block_->last_environment();
-  instr->set_environment(CreateEnvironment(hydrogen_env));
+  int argument_index_accumulator = 0;
+  instr->set_environment(CreateEnvironment(hydrogen_env,
+                                           &argument_index_accumulator));
   return instr;
 }
 
@@ -989,10 +991,13 @@ void LChunkBuilder::VisitInstruction(HInstruction* current) {
 }
 
 
-LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
+LEnvironment* LChunkBuilder::CreateEnvironment(
+    HEnvironment* hydrogen_env,
+    int* argument_index_accumulator) {
   if (hydrogen_env == NULL) return NULL;
 
-  LEnvironment* outer = CreateEnvironment(hydrogen_env->outer());
+  LEnvironment* outer =
+      CreateEnvironment(hydrogen_env->outer(), argument_index_accumulator);
   int ast_id = hydrogen_env->ast_id();
   ASSERT(ast_id != AstNode::kNoNumber);
   int value_count = hydrogen_env->length();
@@ -1002,7 +1007,6 @@ LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
                                           argument_count_,
                                           value_count,
                                           outer);
-  int argument_index = 0;
   for (int i = 0; i < value_count; ++i) {
     if (hydrogen_env->is_special_index(i)) continue;
 
@@ -1011,7 +1015,7 @@ LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
     if (value->IsArgumentsObject()) {
       op = NULL;
     } else if (value->IsPushArgument()) {
-      op = new LArgument(argument_index++);
+      op = new LArgument((*argument_index_accumulator)++);
     } else {
       op = UseAny(value);
     }