Swap bitfield3 and backpointer.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 2012a5ad9d304b0c5c3ebb47c5c4c4283b64d4cc..21ba1d154040dc07c93feafc8ade302acdd2b482 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -669,6 +669,19 @@ void MacroAssembler::AbortIfNotSmi(Register object) {
 }
 
 
+void MacroAssembler::AbortIfNotFixedArray(Register object) {
+  Label ok, fail;
+  CheckMap(object,
+           isolate()->factory()->fixed_array_map(),
+           &fail,
+           DONT_DO_SMI_CHECK);
+  jmp(&ok);
+  bind(&fail);
+  Abort("Operand is not a fixed array");
+  bind(&ok);
+}
+
+
 void MacroAssembler::AbortIfNotString(Register object) {
   test(object, Immediate(kSmiTagMask));
   Assert(not_equal, "Operand is not a string");
@@ -2518,12 +2531,22 @@ void MacroAssembler::Abort(const char* msg) {
 
 void MacroAssembler::LoadInstanceDescriptors(Register map,
                                              Register descriptors) {
-  mov(descriptors,
-      FieldOperand(map, Map::kInstanceDescriptorsOrBitField3Offset));
-  Label not_smi;
-  JumpIfNotSmi(descriptors, &not_smi);
+  mov(descriptors, FieldOperand(map,
+                                Map::kInstanceDescriptorsOrBackPointerOffset));
+
+  Label ok, fail;
+  CheckMap(descriptors,
+           isolate()->factory()->fixed_array_map(),
+           &fail,
+           DONT_DO_SMI_CHECK);
+  jmp(&ok);
+  bind(&fail);
   mov(descriptors, isolate()->factory()->empty_descriptor_array());
-  bind(&not_smi);
+  bind(&ok);
+
+  if (emit_debug_code()) {
+    AbortIfNotFixedArray(descriptors);

[Jakob Kummerow, 2012/07/10 12:26:25]

This check is pretty pointless, don't you think? You only get here if you either
just passed the fixed_array_map() check, or after loading
empty_descriptor_array() (which we can probably trust to be a FixedArray; if you
think we can't, an
ASSERT(isolate->factory()->empty_descriptor_array()->IsFixedArray() at
crankshafting time would be quite sufficient).

[Toon Verwaest, 2012/07/10 13:28:28]

Done.

[Toon Verwaest, 2012/07/10 13:28:28]

Done.

+  }
 }
 
 
@@ -2886,8 +2909,15 @@ void MacroAssembler::CheckEnumCache(Label* call_runtime) {
   // check for an enum cache.  Leave the map in ebx for the subsequent
   // prototype load.
   mov(ebx, FieldOperand(ecx, HeapObject::kMapOffset));
-  mov(edx, FieldOperand(ebx, Map::kInstanceDescriptorsOrBitField3Offset));
-  JumpIfSmi(edx, call_runtime);
+  mov(edx, FieldOperand(ebx, Map::kInstanceDescriptorsOrBackPointerOffset));
+  CheckMap(edx,
+           isolate()->factory()->fixed_array_map(),
+           call_runtime,
+           DONT_DO_SMI_CHECK);
+
+  if (emit_debug_code()) {
+    AbortIfNotFixedArray(edx);

[Jakob Kummerow, 2012/07/10 12:26:25]

This check is entirely pointless. We just did a map check on edx.

[Toon Verwaest, 2012/07/10 13:28:28]

Done.

[Toon Verwaest, 2012/07/10 13:28:28]

Done.

+  }
 
   // Check that there is an enum cache in the non-empty instance
   // descriptors (edx).  This is the case if the next enumeration