Fix issue 979.

src/hydrogen.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4515 matching lines @@
   ASSERT(var == NULL || prop == NULL);
   bool inc = expr->op() == Token::INC;
 
   if (var != NULL) {
     if (!var->is_global() && !var->IsStackAllocated()) {
       BAILOUT("non-stack/non-global variable in count operation");
     }
 
     VISIT_FOR_VALUE(target);
 
-    HValue* value = Pop();
-    HInstruction* instr = BuildIncrement(value, inc);
-    AddInstruction(instr);
-
-    if (expr->is_prefix()) {
-      Push(instr);
-    } else {
-      Push(value);
-    }
+    // Match the full code generator stack by simulating an extra stack
+    // element for postfix operations in a non-effect context.
+    bool has_extra = expr->is_postfix() && !ast_context()->IsEffect();
+    HValue* before = has_extra ? Top() : Pop();
+    HInstruction* after = BuildIncrement(before, inc);
+    AddInstruction(after);
+    Push(after);
 
     if (var->is_global()) {
       HandleGlobalVariableAssignment(var,
-                                     instr,
+                                     after,
                                      expr->position(),
                                      expr->AssignmentId());
     } else {
       ASSERT(var->IsStackAllocated());
-      Bind(var, instr);
+      Bind(var, after);
     }
-    ast_context()->ReturnValue(Pop());
+    Drop(has_extra ? 2 : 1);
+    ast_context()->ReturnValue(expr->is_postfix() ? before : after);
 
   } else if (prop != NULL) {
     prop->RecordTypeFeedback(oracle());
 
     if (prop->key()->IsPropertyName()) {
       // Named property.
 
       // Match the full code generator stack by simulating an extra stack
-      // element for postfix operations in a value context.
+      // element for postfix operations in a non-effect context.
       bool has_extra = expr->is_postfix() && !ast_context()->IsEffect();
       if (has_extra) Push(graph_->GetConstantUndefined());
 
       VISIT_FOR_VALUE(prop->obj());
       HValue* obj = Top();
 
       HInstruction* load = NULL;
       if (prop->IsMonomorphic()) {
         Handle<String> name = prop->key()->AsLiteral()->AsPropertyName();
         Handle<Map> map = prop->GetReceiverTypes()->first();
@@ skipping 20 matching lines @@
       if (has_extra) environment()->SetExpressionStackAt(1, before);
       if (store->HasSideEffects()) AddSimulate(expr->AssignmentId());
       Drop(has_extra ? 2 : 1);
 
       ast_context()->ReturnValue(expr->is_postfix() ? before : after);
 
     } else {
       // Keyed property.
 
       // Match the full code generator stack by simulate an extra stack element
-      // for postfix operations in a value context.
+      // for postfix operations in a non-effect context.
       bool has_extra = expr->is_postfix() && !ast_context()->IsEffect();
       if (has_extra) Push(graph_->GetConstantUndefined());
 
       VISIT_FOR_VALUE(prop->obj());
       VISIT_FOR_VALUE(prop->key());
       HValue* obj = environment()->ExpressionStackAt(1);
       HValue* key = environment()->ExpressionStackAt(0);
 
       bool is_fast_elements = prop->IsMonomorphic() &&
           prop->GetMonomorphicReceiverType()->has_fast_elements();
@@ skipping 1052 matching lines @@
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (chunk_ != NULL) chunk_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal