Revert of Provide a tagged allocation top pointer.

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 ff3a0c961018db55b192a5df01e4d49981619f0b..0dd37dd4aebdf3e113bdf385cc201024dea01506 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -2032,7 +2032,7 @@
     // Align the next allocation. Storing the filler map without checking top is
     // safe in new-space because the limit of the heap is aligned there.
     STATIC_ASSERT(kPointerAlignment * 2 == kDoubleAlignment);
-    and_(result_end, result, Operand(kDoubleAlignmentMaskTagged), SetCC);
+    and_(result_end, result, Operand(kDoubleAlignmentMask), SetCC);
     Label aligned;
     b(eq, &aligned);
     if ((flags & PRETENURE) != 0) {
@@ -2040,8 +2040,7 @@
       b(hs, gc_required);
     }
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
-    str(result_end, MemOperand(result, -kHeapObjectTag));
-    add(result_end, result_end, Operand(kDoubleSize / 2));
+    str(result_end, MemOperand(result, kDoubleSize / 2, PostIndex));
     bind(&aligned);
   }
 
@@ -2074,6 +2073,9 @@
     // The top pointer is not updated for allocation folding dominators.
     str(result_end, MemOperand(top_address));
   }
+
+  // Tag object.
+  add(result, result, Operand(kHeapObjectTag));
 }
 
 
@@ -2136,7 +2138,7 @@
     // Align the next allocation. Storing the filler map without checking top is
     // safe in new-space because the limit of the heap is aligned there.
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
-    and_(result_end, result, Operand(kDoubleAlignmentMaskTagged), SetCC);
+    and_(result_end, result, Operand(kDoubleAlignmentMask), SetCC);
     Label aligned;
     b(eq, &aligned);
     if ((flags & PRETENURE) != 0) {
@@ -2144,8 +2146,7 @@
       b(hs, gc_required);
     }
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
-    str(result_end, MemOperand(result, -kHeapObjectTag));
-    add(result_end, result_end, Operand(kDoubleSize / 2));
+    str(result_end, MemOperand(result, kDoubleSize / 2, PostIndex));
     bind(&aligned);
   }
 
@@ -2164,12 +2165,15 @@
   // Update allocation top. result temporarily holds the new top.
   if (emit_debug_code()) {
     tst(result_end, Operand(kObjectAlignmentMask));
-    Check(ne, kUnalignedAllocationInNewSpace);
+    Check(eq, kUnalignedAllocationInNewSpace);
   }
   if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
     // The top pointer is not updated for allocation folding dominators.
     str(result_end, MemOperand(top_address));
   }
+
+  // Tag object.
+  add(result, result, Operand(kHeapObjectTag));
 }
 
 void MacroAssembler::FastAllocate(Register object_size, Register result,
@@ -2192,12 +2196,11 @@
     // Align the next allocation. Storing the filler map without checking top is
     // safe in new-space because the limit of the heap is aligned there.
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
-    and_(result_end, result, Operand(kDoubleAlignmentMaskTagged), SetCC);
+    and_(result_end, result, Operand(kDoubleAlignmentMask), SetCC);
     Label aligned;
     b(eq, &aligned);
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
-    str(result_end, MemOperand(result, -kHeapObjectTag));
-    add(result_end, result_end, Operand(kDoubleSize / 2));
+    str(result_end, MemOperand(result, kDoubleSize / 2, PostIndex));
     bind(&aligned);
   }
 
@@ -2212,10 +2215,12 @@
   // Update allocation top. result temporarily holds the new top.
   if (emit_debug_code()) {
     tst(result_end, Operand(kObjectAlignmentMask));
-    Check(ne, kUnalignedAllocationInNewSpace);
+    Check(eq, kUnalignedAllocationInNewSpace);
   }
   // The top pointer is not updated for allocation folding dominators.
   str(result_end, MemOperand(top_address));
+
+  add(result, result, Operand(kHeapObjectTag));
 }
 
 void MacroAssembler::FastAllocate(int object_size, Register result,
@@ -2243,12 +2248,11 @@
     // Align the next allocation. Storing the filler map without checking top is
     // safe in new-space because the limit of the heap is aligned there.
     STATIC_ASSERT(kPointerAlignment * 2 == kDoubleAlignment);
-    and_(result_end, result, Operand(kDoubleAlignmentMaskTagged), SetCC);
+    and_(result_end, result, Operand(kDoubleAlignmentMask), SetCC);
     Label aligned;
     b(eq, &aligned);
     mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
-    str(result_end, MemOperand(result, -kHeapObjectTag));
-    add(result_end, result_end, Operand(kDoubleSize / 2));
+    str(result_end, MemOperand(result, kDoubleSize / 2, PostIndex));
     bind(&aligned);
   }
 
@@ -2276,6 +2280,8 @@
 
   // The top pointer is not updated for allocation folding dominators.
   str(result_end, MemOperand(top_address));
+
+  add(result, result, Operand(kHeapObjectTag));
 }
 
 void MacroAssembler::AllocateTwoByteString(Register result,