[Interpreter] Fix a register allocation bug and add a DCHECK.

test/cctest/interpreter/test-bytecode-generator.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-array-iterator.h"
 #include "src/interpreter/bytecode-generator.h"
 #include "src/interpreter/interpreter.h"
@@ skipping 2970 matching lines @@
 
 
 TEST(CountOperators) {
   InitializedHandleScope handle_scope;
   BytecodeGeneratorHelper helper;
   Zone zone;
 
   FeedbackVectorSpec feedback_spec(&zone);
   FeedbackVectorSlot slot1 = feedback_spec.AddLoadICSlot();
   FeedbackVectorSlot slot2 = feedback_spec.AddStoreICSlot();
-
   Handle<i::TypeFeedbackVector> vector =
       i::NewTypeFeedbackVector(helper.isolate(), &feedback_spec);
 
+  FeedbackVectorSpec store_feedback_spec(&zone);
+  FeedbackVectorSlot store_slot = store_feedback_spec.AddStoreICSlot();
+  Handle<i::TypeFeedbackVector> store_vector =
+      i::NewTypeFeedbackVector(helper.isolate(), &store_feedback_spec);
+
   int closure = Register::function_closure().index();
   int first_context_slot = Context::MIN_CONTEXT_SLOTS;
 
   int object_literal_flags =
       ObjectLiteral::kFastElements | ObjectLiteral::kDisableMementos;
+  int array_literal_flags =
+      ArrayLiteral::kDisableMementos | ArrayLiteral::kShallowElements;
 
   ExpectedSnippet<InstanceType> snippets[] = {
       {"var a = 1; return ++a;",
        1 * kPointerSize,
        1,
        11,
        {
            B(LdaSmi8), U8(1),  //
            B(Star), R(0),      //
            B(Ldar), R(0),      //
@@ skipping 162 matching lines @@
            B(LdaContextSlot), R(1), U8(first_context_slot),                //
            B(ToNumber),                                                    //
            B(Star), R(2),                                                  //
            B(Dec),                                                         //
            B(StaContextSlot), R(1), U8(first_context_slot),                //
            B(Ldar), R(2),                                                  //
            B(Return),                                                      //
        },
        1,
        {InstanceType::SHARED_FUNCTION_INFO_TYPE}},
+      {"var idx = 1; var a = [1, 2]; return a[idx++] = 2;",
+       3 * kPointerSize,
+       1,
+       26,
+       {
+           B(LdaSmi8), U8(1),                                              //
+           B(Star), R(0),                                                  //
+           B(LdaConstant), U8(0),                                          //
+           B(CreateArrayLiteral), U8(0), U8(array_literal_flags),          //
+           B(Star), R(1),                                                  //
+           B(Ldar), R(0),                                                  //
+           B(ToNumber),                                                    //
+           B(Star), R(2),                                                  //
+           B(Inc),                                                         //
+           B(Star), R(0),                                                  //
+           B(LdaSmi8), U8(2),                                              //
+           B(KeyedStoreICSloppy), R(1), R(2),                              //
+                                  U8(store_vector->GetIndex(store_slot)),  //
+           B(Return),                                                      //
+       },
+       1,
+       {InstanceType::FIXED_ARRAY_TYPE}},
   };
 
   for (size_t i = 0; i < arraysize(snippets); i++) {
     Handle<BytecodeArray> bytecode_array =
         helper.MakeBytecodeForFunctionBody(snippets[i].code_snippet);
     CheckBytecodeArrayEqual(snippets[i], bytecode_array);
   }
 }
 
 
@@ skipping 414 matching lines @@
   for (size_t i = 0; i < arraysize(snippets); i++) {
     Handle<BytecodeArray> bytecode_array =
         helper.MakeBytecodeForFunctionBody(snippets[i].code_snippet);
     CheckBytecodeArrayEqual(snippets[i], bytecode_array);
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8