[compiler] Verify that type feedback vector structure is the same on recompile.

src/compiler.cc

 // Copyright 2012 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/compiler.h"
 
 #include <algorithm>
 
 #include "src/ast-numbering.h"
 #include "src/bootstrapper.h"
@@ skipping 193 matching lines @@
 bool CompilationInfo::ShouldSelfOptimize() {
   return FLAG_crankshaft &&
          !(function()->flags() & AstProperties::kDontSelfOptimize) &&
          !function()->dont_optimize() &&
          function()->scope()->AllowsLazyCompilation() &&
          (!has_shared_info() || !shared_info()->optimization_disabled());
 }
 
 
 void CompilationInfo::EnsureFeedbackVector() {
-  if (feedback_vector_.is_null() ||
-      feedback_vector_->SpecDiffersFrom(function()->feedback_vector_spec())) {
+  if (feedback_vector_.is_null()) {
     feedback_vector_ = isolate()->factory()->NewTypeFeedbackVector(
         function()->feedback_vector_spec());
   }
+
+  // It's very important that recompiles do not alter the structure of the
+  // type feedback vector.
+  CHECK(!feedback_vector_->SpecDiffersFrom(function()->feedback_vector_spec()));
 }
 
 
 bool CompilationInfo::is_simple_parameter_list() {
   return scope()->is_simple_parameter_list();
 }
 
 
 bool CompilationInfo::MayUseThis() const {
   return scope()->has_this_declaration() && scope()->receiver()->is_used();
@@ skipping 1441 matching lines @@
 
 
 #if DEBUG
 void CompilationInfo::PrintAstForTesting() {
   PrintF("--- Source from AST ---\n%s\n",
          PrettyPrinter(isolate(), zone()).PrintProgram(function()));
 }
 #endif
 }  // namespace internal
 }  // namespace v8