Add complete ElementKind information directly to Map for objects with elements.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index 3736ecd8ab53a60dcaee72949d9ab17afa1bcd70..d4d66d277c0f46c9b418b04d5d4d921045d581ea 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -1676,6 +1676,15 @@ void MacroAssembler::CompareRoot(Register obj,
 }
 
 
+void MacroAssembler::CheckFastElements(Register map,
+                                       Register scratch,
+                                       Label* fail) {
+  ldrb(scratch, FieldMemOperand(map, Map::kInstanceTypeOffset));
+  cmp(scratch, Operand(Map::kMaximumBitField2FastElementValue));

[Mads Ager (chromium), 2011/05/30 11:14:24]

Can we add some sort of STATIC_ASSERT here that will trigger if we change the
order of stuff so that it will no longer be safe to only check the top value?

Something like FAST_ELEMENTS == 0?

[danno, 2011/06/01 22:29:54]

Done.

+  b(hi, fail);
+}
+
+
 void MacroAssembler::CheckMap(Register obj,
                               Register scratch,
                               Handle<Map> map,