Reland parts of 'Use weak cells in map checks in polymorphic ICs'

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index 8129470e158cfa719501209d5fa601f20646e56b..240b8f6df13cd61de3cfc5ae87430eab7d69dedc 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -5019,7 +5019,6 @@ void LCodeGen::DoDeclareGlobals(LDeclareGlobals* instr) {
   Register scratch2 = x6;
   DCHECK(instr->IsMarkedAsCall());
 
-  ASM_UNIMPLEMENTED_BREAK("DoDeclareGlobals");

[mvstanton, 2014/12/02 13:45:20]

What is this about?

[ulan, 2014/12/02 13:56:06]

DoDeclareGlobals is actually implemented. The assert was there as a guard
because DoDeclareGlobals wasn't used in any of our tests. It starts triggering
in one of the tests if maps polymorphic ICs are weak.

   // TODO(all): if Mov could handle object in new space then it could be used
   // here.
   __ LoadHeapObject(scratch1, instr->hydrogen()->pairs());