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

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
diff --git a/runtime/vm/stub_code_arm.cc b/runtime/vm/stub_code_arm.cc
index 14fe95c825941b3af74f1d20de70111b6b6f4d30..00d0201ae4c10de83e2913410d5ebfc826a6a620 100644
--- a/runtime/vm/stub_code_arm.cc
+++ b/runtime/vm/stub_code_arm.cc
@@ -703,9 +703,8 @@ void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
 
   // R9: Allocation size.
   Heap::Space space = Heap::kNew;
-  __ ldr(R8, Address(THR, Thread::heap_offset()));
   // Potential new object start.
-  __ ldr(R0, Address(R8, Heap::TopOffset(space)));
+  __ ldr(R0, Address(THR, Thread::top_offset()));
   __ adds(NOTFP, R0, Operand(R9));  // Potential next object start.
   __ b(&slow_case, CS);             // Branch if unsigned overflow.
 
@@ -713,14 +712,14 @@ void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
   // R0: potential new object start.
   // NOTFP: potential next object start.
   // R9: allocation size.
-  __ ldr(R3, Address(R8, Heap::EndOffset(space)));
+  __ ldr(R3, Address(THR, Thread::end_offset()));
   __ cmp(NOTFP, Operand(R3));
   __ b(&slow_case, CS);
 
   // Successfully allocated the object(s), now update top to point to
   // next object start and initialize the object.
   NOT_IN_PRODUCT(__ LoadAllocationStatsAddress(R3, cid));
-  __ str(NOTFP, Address(R8, Heap::TopOffset(space)));
+  __ str(R7, Address(THR, Thread::top_offset()));
   __ add(R0, R0, Operand(kHeapObjectTag));
 
   // Initialize the tags.
@@ -930,8 +929,7 @@ void StubCode::GenerateAllocateContextStub(Assembler* assembler) {
     // R2: object size.
     const intptr_t cid = kContextCid;
     Heap::Space space = Heap::kNew;
-    __ ldr(R9, Address(THR, Thread::heap_offset()));
-    __ ldr(R0, Address(R9, Heap::TopOffset(space)));
+    __ ldr(R0, Address(THR, Thread::top_offset()));
     __ add(R3, R2, Operand(R0));
     // Check if the allocation fits into the remaining space.
     // R0: potential new object.
@@ -939,7 +937,7 @@ void StubCode::GenerateAllocateContextStub(Assembler* assembler) {
     // R2: object size.
     // R3: potential next object start.
     // R9: heap.
-    __ ldr(IP, Address(R9, Heap::EndOffset(space)));
+    __ ldr(IP, Address(THR, Thread::end_offset()));
     __ cmp(R3, Operand(IP));
     if (FLAG_use_slow_path) {
       __ b(&slow_case);
@@ -955,7 +953,7 @@ void StubCode::GenerateAllocateContextStub(Assembler* assembler) {
     // R3: next object start.
     // R9: heap.
     NOT_IN_PRODUCT(__ LoadAllocationStatsAddress(R4, cid));
-    __ str(R3, Address(R9, Heap::TopOffset(space)));
+    __ str(R3, Address(THR, Thread::top_offset()));
     __ add(R0, R0, Operand(kHeapObjectTag));
 
     // Calculate the size tag.
@@ -1128,21 +1126,20 @@ void StubCode::GenerateAllocationStubForClass(Assembler* assembler,
     // Allocate the object and update top to point to
     // next object start and initialize the allocated object.
     Heap::Space space = Heap::kNew;
-    __ ldr(R9, Address(THR, Thread::heap_offset()));
-    __ ldr(R0, Address(R9, Heap::TopOffset(space)));
+    __ ldr(R0, Address(THR, Thread::top_offset()));
     __ AddImmediate(R1, R0, instance_size);
     // Check if the allocation fits into the remaining space.
     // R0: potential new object start.
     // R1: potential next object start.
     // R9: heap.
-    __ ldr(IP, Address(R9, Heap::EndOffset(space)));
+    __ ldr(IP, Address(THR, Thread::end_offset()));
     __ cmp(R1, Operand(IP));
     if (FLAG_use_slow_path) {
       __ b(&slow_case);
     } else {
       __ b(&slow_case, CS);  // Unsigned higher or equal.
     }
-    __ str(R1, Address(R9, Heap::TopOffset(space)));
+    __ str(R1, Address(THR, Thread::top_offset()));
 
     // Load the address of the allocation stats table. We split up the load
     // and the increment so that the dependent load is not too nearby.