Implement tracking and optimizations of packed arrays

src/x64/lithium-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1994 matching lines @@
   ASSERT(instr->value()->representation().IsTagged());
 
   LStoreKeyedGeneric* result =
       new(zone()) LStoreKeyedGeneric(object, key, value);
   return MarkAsCall(result, instr);
 }
 
 
 LInstruction* LChunkBuilder::DoTransitionElementsKind(
     HTransitionElementsKind* instr) {
-  if (instr->original_map()->elements_kind() == FAST_SMI_ONLY_ELEMENTS &&
-      instr->transitioned_map()->elements_kind() == FAST_ELEMENTS) {
+  ElementsKind from_kind = instr->original_map()->elements_kind();
+  ElementsKind to_kind = instr->transitioned_map()->elements_kind();
+  bool simple_map_change = (GetHoleyElementsKind(from_kind) == to_kind) ||

[Jakob Kummerow, 2012/05/22 17:36:49]

This computation is used often enough that it would be nice to factor it out
into elements-kind.h:

bool IsSimpleMapChange(ElementsKind from_kind, ElementsKind to_kind) {
  return (GetHoleyElementsKind(from_kind) == to_kind) ||
      (IsFastSmiElementsKind(from_kind) &&
      IsFastObjectElementsKind(to_kind));
}

But then again, this CL is large enough as it is, so feel free to postpone such
cleanup.

[danno, 2012/05/23 14:25:36]

Done.

+      (IsFastSmiElementsKind(from_kind) &&
+       IsFastObjectElementsKind(to_kind));
+  if (simple_map_change) {
     LOperand* object = UseRegister(instr->object());
     LOperand* new_map_reg = TempRegister();
     LOperand* temp_reg = TempRegister();
     LTransitionElementsKind* result =
         new(zone()) LTransitionElementsKind(object, new_map_reg, temp_reg);
     return DefineSameAsFirst(result);
   } else {
     LOperand* object = UseFixed(instr->object(), rax);
     LOperand* fixed_object_reg = FixedTemp(rdx);
     LOperand* new_map_reg = FixedTemp(rbx);
@@ skipping 288 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64