Moves the top_ and end_ words of the Scavenger into mutator thread.

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
diff --git a/runtime/vm/intrinsifier_x64.cc b/runtime/vm/intrinsifier_x64.cc
index f0ca5913f9164fb4d092aecb7eee663df629afac..0473f2780802d18fa1f877cdd8aec848e33f41f0 100644
--- a/runtime/vm/intrinsifier_x64.cc
+++ b/runtime/vm/intrinsifier_x64.cc
@@ -175,8 +175,7 @@ void Intrinsifier::GrowableArray_add(Assembler* assembler) {
   __ leaq(RDI, Address(RDI, scale_factor, fixed_size_plus_alignment_padding)); \
   __ andq(RDI, Immediate(-kObjectAlignment));                                  \
   Heap::Space space = Heap::kNew;                                              \
-  __ movq(R13, Address(THR, Thread::heap_offset()));                           \
-  __ movq(RAX, Address(R13, Heap::TopOffset(space)));                          \
+  __ movq(RAX, Address(THR, Thread::top_offset()));                            \
   __ movq(RCX, RAX);                                                           \
                                                                                \
   /* RDI: allocation size. */                                                  \
@@ -188,12 +187,12 @@ void Intrinsifier::GrowableArray_add(Assembler* assembler) {
   /* RCX: potential next object start. */                                      \
   /* RDI: allocation size. */                                                  \
   /* R13: heap. */                                                             \
-  __ cmpq(RCX, Address(R13, Heap::EndOffset(space)));                          \
+  __ cmpq(RCX, Address(THR, Thread::end_offset()));                            \
   __ j(ABOVE_EQUAL, &fall_through);                                            \
                                                                                \
   /* Successfully allocated the object(s), now update top to point to */       \
   /* next object start and initialize the object. */                           \
-  __ movq(Address(R13, Heap::TopOffset(space)), RCX);                          \
+  __ movq(Address(THR, Thread::top_offset()), RCX);                            \
   __ addq(RAX, Immediate(kHeapObjectTag));                                     \
   NOT_IN_PRODUCT(__ UpdateAllocationStatsWithSize(cid, RDI, space));           \
   /* Initialize the tags. */                                                   \
@@ -2009,8 +2008,7 @@ static void TryAllocateOnebyteString(Assembler* assembler,
 
   const intptr_t cid = kOneByteStringCid;
   Heap::Space space = Heap::kNew;
-  __ movq(R13, Address(THR, Thread::heap_offset()));
-  __ movq(RAX, Address(R13, Heap::TopOffset(space)));
+  __ movq(RAX, Address(THR, Thread::top_offset()));
 
   // RDI: allocation size.
   __ movq(RCX, RAX);
@@ -2021,13 +2019,12 @@ static void TryAllocateOnebyteString(Assembler* assembler,
   // RAX: potential new object start.
   // RCX: potential next object start.
   // RDI: allocation size.
-  // R13: heap.
-  __ cmpq(RCX, Address(R13, Heap::EndOffset(space)));
+  __ cmpq(RCX, Address(THR, Thread::end_offset()));
   __ j(ABOVE_EQUAL, &pop_and_fail);
 
   // Successfully allocated the object(s), now update top to point to
   // next object start and initialize the object.
-  __ movq(Address(R13, Heap::TopOffset(space)), RCX);
+  __ movq(Address(THR, Thread::top_offset()), RCX);
   __ addq(RAX, Immediate(kHeapObjectTag));
   NOT_IN_PRODUCT(__ UpdateAllocationStatsWithSize(cid, RDI, space));