[compiler] Reduce the code size of the ToBoolean stub.

src/code-stubs.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/code-stubs.h"
 
 #include <sstream>
 
 #include "src/bootstrapper.h"
 #include "src/code-factory.h"
@@ skipping 1568 matching lines @@
 
     assembler->Bind(&if_valueiszero);
     assembler->Return(assembler->BooleanConstant(false));
 
     assembler->Bind(&if_valueisnotzero);
     assembler->Return(assembler->BooleanConstant(true));
   }
 
   assembler->Bind(&if_valueisnotsmi);
   {
-    Label if_valueisstring(assembler), if_valueisheapnumber(assembler),
-        if_valueisoddball(assembler), if_valueisother(assembler);
+    Label if_valueisstring(assembler), if_valueisnotstring(assembler),
+        if_valueisheapnumber(assembler), if_valueisoddball(assembler),
+        if_valueisother(assembler);
 
     // The {value} is a HeapObject, load its map.
     Node* value_map = assembler->LoadObjectField(value, HeapObject::kMapOffset);
 
     // Load the {value}s instance type.
     Node* value_instancetype = assembler->Load(
         MachineType::Uint8(), value_map,
         assembler->IntPtrConstant(Map::kInstanceTypeOffset - kHeapObjectTag));
 
     // Dispatch based on the instance type; we distinguish all String instance
     // types, the HeapNumber type and the Oddball type.
-    size_t const kNumCases = FIRST_NONSTRING_TYPE + 2;
+    assembler->Branch(
+        assembler->Int32LessThan(
+            value_instancetype, assembler->Int32Constant(FIRST_NONSTRING_TYPE)),
+        &if_valueisstring, &if_valueisnotstring);
+    assembler->Bind(&if_valueisnotstring);
+    size_t const kNumCases = 2;
     Label* case_labels[kNumCases];
     int32_t case_values[kNumCases];
-    for (int32_t i = 0; i < FIRST_NONSTRING_TYPE; ++i) {
-      case_labels[i] = new Label(assembler);
-      case_values[i] = i;
-    }
-    case_labels[FIRST_NONSTRING_TYPE + 0] = &if_valueisheapnumber;
-    case_values[FIRST_NONSTRING_TYPE + 0] = HEAP_NUMBER_TYPE;
-    case_labels[FIRST_NONSTRING_TYPE + 1] = &if_valueisoddball;
-    case_values[FIRST_NONSTRING_TYPE + 1] = ODDBALL_TYPE;
+    case_labels[0] = &if_valueisheapnumber;
+    case_values[0] = HEAP_NUMBER_TYPE;
+    case_labels[1] = &if_valueisoddball;
+    case_values[1] = ODDBALL_TYPE;
     assembler->Switch(value_instancetype, &if_valueisother, case_values,
                       case_labels, arraysize(case_values));
-    for (int32_t i = 0; i < FIRST_NONSTRING_TYPE; ++i) {
-      assembler->Bind(case_labels[i]);
-      assembler->Goto(&if_valueisstring);
-      delete case_labels[i];
-    }
 
     assembler->Bind(&if_valueisstring);
     {
       // Load the string length field of the {value}.
       Node* value_length =
           assembler->LoadObjectField(value, String::kLengthOffset);
 
       // Check if the {value} is the empty string.
       Label if_valueisempty(assembler), if_valueisnotempty(assembler);
       assembler->Branch(
           assembler->SmiEqual(value_length, assembler->SmiConstant(0)),
           &if_valueisempty, &if_valueisnotempty);
 
       assembler->Bind(&if_valueisempty);
       assembler->Return(assembler->BooleanConstant(false));

[Benedikt Meurer, 2016/04/21 18:04:13]

You could even further reduce code size by having shared return_true and
return_false labels, now that we do automatic-edge-split-form.

 
       assembler->Bind(&if_valueisnotempty);
       assembler->Return(assembler->BooleanConstant(true));
     }
 
     assembler->Bind(&if_valueisheapnumber);
     {
       Node* value_value = assembler->Load(
           MachineType::Float64(), value,
           assembler->IntPtrConstant(HeapNumber::kValueOffset - kHeapObjectTag));
@@ skipping 481 matching lines @@
   if (type->Is(Type::UntaggedPointer())) {
     return Representation::External();
   }
 
   DCHECK(!type->Is(Type::Untagged()));
   return Representation::Tagged();
 }
 
 }  // namespace internal
 }  // namespace v8