[turbofan] Collect and use type feedback on ToNumber.

src/interpreter/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/interpreter/bytecode-generator.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-stubs.h"
@@ skipping 2958 matching lines @@
           property->obj()->AsSuperPropertyReference();
       VisitForRegisterValue(super_property->this_var(), load_super_args[0]);
       VisitForRegisterValue(super_property->home_object(), load_super_args[1]);
       VisitForRegisterValue(property->key(), load_super_args[2]);
       builder()->CallRuntime(Runtime::kLoadKeyedFromSuper, load_super_args);
       break;
     }
   }
 
   // Save result for postfix expressions.
+  FeedbackSlot count_slot = expr->CountBinaryOpFeedbackSlot();

[rmcilroy, 2017/04/06 11:21:31]

Hmm, we are now recording this type feedback twice. I guess this is fine for
now, but it suggests we should rework this since the only place we use either
the ToNumber or Count bytecodes is for count operations. Maybe we can think
about having a single bytecode for CountPostfix (need to think about how we
deopt though) ? WDYT?

[Benedikt Meurer, 2017/04/06 11:30:00]

I'd be in favor of that long-/middle-term. I'll put a TODO here.

   if (is_postfix) {
     // Convert old value into a number before saving it.
     old_value = register_allocator()->NewRegister();
     builder()
-        ->ConvertAccumulatorToNumber(old_value)
+        ->ConvertAccumulatorToNumber(old_value, feedback_index(count_slot))
         .LoadAccumulatorWithRegister(old_value);
   }
 
   // Perform +1/-1 operation.
-  FeedbackSlot slot = expr->CountBinaryOpFeedbackSlot();
-  builder()->CountOperation(expr->binary_op(), feedback_index(slot));
+  builder()->CountOperation(expr->binary_op(), feedback_index(count_slot));
 
   // Store the value.
   builder()->SetExpressionPosition(expr);
   FeedbackSlot feedback_slot = expr->CountSlot();
   switch (assign_type) {
     case VARIABLE: {
       VariableProxy* proxy = expr->expression()->AsVariableProxy();
       BuildVariableAssignment(proxy->var(), expr->op(), feedback_slot,
                               proxy->hole_check_mode());
       break;
@@ skipping 623 matching lines @@
 }
 
 Runtime::FunctionId BytecodeGenerator::StoreKeyedToSuperRuntimeId() {
   return is_strict(language_mode()) ? Runtime::kStoreKeyedToSuper_Strict
                                     : Runtime::kStoreKeyedToSuper_Sloppy;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8