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 5dbf000c9286a012383f291f6699f1e793ab6f6f..9aa67811cd6733900a64535e097cdee9448d6fe8 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -367,7 +367,9 @@
   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);
@@ -385,9 +387,8 @@
   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 =