PPC: Support fast-path allocation for subclass constructors with correctly initialized initial maps.

src/ppc/builtins-ppc.cc

 // Copyright 2014 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.
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 378 matching lines @@
     // the preconditions is not met, the code bails out to the runtime call.
     Label rt_call, allocated;
     if (FLAG_inline_new) {
       ExternalReference debug_step_in_fp =
           ExternalReference::debug_step_in_fp_address(isolate);
       __ mov(r5, Operand(debug_step_in_fp));
       __ LoadP(r5, MemOperand(r5));
       __ cmpi(r5, Operand::Zero());
       __ bne(&rt_call);
 
-      // Fall back to runtime if the original constructor and function differ.
-      __ cmp(r4, r6);
+      // Verify that the original constructor is a JSFunction.
+      __ CompareObjectType(r6, r8, r7, JS_FUNCTION_TYPE);
       __ bne(&rt_call);
 
       // Load the initial map and verify that it is in fact a map.
-      // r4: constructor function
+      // r6: original constructor
       __ LoadP(r5,
-               FieldMemOperand(r4, JSFunction::kPrototypeOrInitialMapOffset));
+               FieldMemOperand(r6, JSFunction::kPrototypeOrInitialMapOffset));
       __ JumpIfSmi(r5, &rt_call);
       __ CompareObjectType(r5, r8, r7, MAP_TYPE);
       __ bne(&rt_call);
 
+      // Fall back to runtime if the expected base constructor and base
+      // constructor differ.
+      __ LoadP(r8, FieldMemOperand(r5, Map::kConstructorOrBackPointerOffset));
+      __ cmp(r4, r8);
+      __ bne(&rt_call);
+
       // Check that the constructor is not constructing a JSFunction (see
       // comments in Runtime_NewObject in runtime.cc). In which case the
       // initial map's instance type would be JS_FUNCTION_TYPE.
       // r4: constructor function
       // r5: initial map
       __ CompareInstanceType(r5, r8, JS_FUNCTION_TYPE);
       __ beq(&rt_call);
 
       if (!is_api_function) {
         Label allocate;
         MemOperand bit_field3 = FieldMemOperand(r5, Map::kBitField3Offset);
         // Check if slack tracking is enabled.
         __ lwz(r7, bit_field3);
         __ DecodeField<Map::Counter>(r11, r7);
         __ cmpi(r11, Operand(Map::kSlackTrackingCounterEnd));
         __ blt(&allocate);
         // Decrease generous allocation count.
         __ Add(r7, r7, -(1 << Map::Counter::kShift), r0);
         __ stw(r7, bit_field3);
         __ cmpi(r11, Operand(Map::kSlackTrackingCounterEnd));
         __ bne(&allocate);
 
-        __ push(r4);
-
-        __ Push(r5, r4);  // r4 = constructor
+        __ Push(r4, r5, r5);  // r5 = initial map
         __ CallRuntime(Runtime::kFinalizeInstanceSize, 1);
 
         __ Pop(r4, r5);
 
         __ bind(&allocate);
       }
 
       // Now allocate the JSObject on the heap.
       // r4: constructor function
       // r5: initial map
@@ skipping 1527 matching lines @@
     __ bkpt(0);
   }
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_PPC