Revert of Provide a tagged allocation top pointer.

src/code-stub-assembler.cc

Index: src/code-stub-assembler.cc
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index 610492f39126bf3819f88d3440c8aafe8595316a..27f39a7f1068e2006f26c5a42d0426687ea85c7c 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -375,7 +375,9 @@
   Node* no_runtime_result = top;
   StoreNoWriteBarrier(MachineType::PointerRepresentation(), top_address,
                       new_top);
-  result.Bind(BitcastWordToTagged(no_runtime_result));
+  no_runtime_result = BitcastWordToTagged(
+      IntPtrAdd(no_runtime_result, IntPtrConstant(kHeapObjectTag)));
+  result.Bind(no_runtime_result);
   Goto(&merge_runtime);
 
   Bind(&merge_runtime);
@@ -393,9 +395,8 @@
   if (flags & kDoubleAlignment) {
     // TODO(epertoso): Simd128 alignment.
     Label aligned(this), not_aligned(this), merge(this, &adjusted_size);
-    Branch(WordAnd(IntPtrSub(top, IntPtrConstant(kHeapObjectTag)),
-                   IntPtrConstant(kDoubleAlignmentMask)),
-           &not_aligned, &aligned);
+    Branch(WordAnd(top, IntPtrConstant(kDoubleAlignmentMask)), &not_aligned,
+           &aligned);
 
     Bind(&not_aligned);
     Node* not_aligned_size =
@@ -421,8 +422,7 @@
   // Store a filler and increase the address by kPointerSize.
   // TODO(epertoso): this code assumes that we only align to kDoubleSize. Change
   // it when Simd128 alignment is supported.
-  StoreNoWriteBarrier(MachineType::PointerRepresentation(),
-                      IntPtrSub(top, IntPtrConstant(1)),
+  StoreNoWriteBarrier(MachineType::PointerRepresentation(), top,
                       LoadRoot(Heap::kOnePointerFillerMapRootIndex));
   address.Bind(BitcastWordToTagged(
       IntPtrAdd(address.value(), IntPtrConstant(kPointerSize))));