PPC: Code cleanup in GenerateRecordCallTarget.

src/ppc/code-stubs-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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 2505 matching lines @@
 }
 
 
 static void CallStubInRecordCallTarget(MacroAssembler* masm, CodeStub* stub) {
   // r3 : number of arguments to the construct function
   // r5 : Feedback vector
   // r6 : slot in feedback vector (Smi)
   // r4 : the function to call
   FrameScope scope(masm, StackFrame::INTERNAL);
 
-  // Arguments register must be smi-tagged to call out.
+  // Number-of-arguments register must be smi-tagged to call out.
   __ SmiTag(r3);
   __ Push(r6, r5, r4, r3);
 
   __ CallStub(stub);
 
   __ Pop(r6, r5, r4, r3);
   __ SmiUntag(r3);
 }
 
 
@@ skipping 12 matching lines @@
   DCHECK_EQ(*TypeFeedbackVector::UninitializedSentinel(masm->isolate()),
             masm->isolate()->heap()->uninitialized_symbol());
 
   // Load the cache state into r7.
   __ SmiToPtrArrayOffset(r7, r6);
   __ add(r7, r5, r7);
   __ LoadP(r7, FieldMemOperand(r7, FixedArray::kHeaderSize));
 
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
+  // We don't know if r7 is a WeakCell or a Symbol, but it's harmless to read at
+  // this position in a symbol (see static asserts in type-feedback-vector.h).
   Label check_allocation_site;
   Register feedback_map = r8;
   Register weak_value = r9;
   __ LoadP(weak_value, FieldMemOperand(r7, WeakCell::kValueOffset));
   __ cmp(r4, weak_value);
   __ beq(&done);
   __ CompareRoot(r7, Heap::kmegamorphic_symbolRootIndex);
   __ beq(&done);
-  __ LoadP(feedback_map, FieldMemOperand(r7, 0));
+  __ LoadP(feedback_map, FieldMemOperand(r7, HeapObject::kMapOffset));
   __ CompareRoot(feedback_map, Heap::kWeakCellMapRootIndex);
   __ bne(FLAG_pretenuring_call_new ? &miss : &check_allocation_site);
 
-  // If r4 is not equal to the weak cell value, and the weak cell value is
-  // cleared, we have a new chance to become monomorphic.
+  // If the weak cell is cleared, we have a new chance to become monomorphic.
   __ JumpIfSmi(weak_value, &initialize);
   __ b(&megamorphic);
 
   if (!FLAG_pretenuring_call_new) {
     __ bind(&check_allocation_site);
     // If we came here, we need to see if we are the array function.
     // If we didn't have a matching function, and we didn't find the megamorph
     // sentinel, then we have in the slot either some other function or an
-    // AllocationSite. Do a map check on the object in ecx.
+    // AllocationSite.
     __ CompareRoot(feedback_map, Heap::kAllocationSiteMapRootIndex);
     __ bne(&miss);
 
     // Make sure the function is the Array() function
     __ LoadGlobalFunction(Context::ARRAY_FUNCTION_INDEX, r7);
     __ cmp(r4, r7);
     __ bne(&megamorphic);
     __ b(&done);
   }
 
@@ skipping 2998 matching lines @@
                            kStackUnwindSpace, NULL,
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_PPC