Provide a tagged allocation top pointer.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 45e1197f4ab2dd7491848740736a76ad06b71582..301d41f08d418b134abed715bd63bd884e589c1d 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1504,7 +1504,7 @@ void MacroAssembler::UpdateAllocationTopHelper(Register result_end,
                                                AllocationFlags flags) {
   if (emit_debug_code()) {
     test(result_end, Immediate(kObjectAlignmentMask));
-    Check(zero, kUnalignedAllocationInNewSpace);
+    Check(not_zero, kUnalignedAllocationInNewSpace);
   }
 
   ExternalReference allocation_top =
@@ -1555,13 +1555,13 @@ void MacroAssembler::Allocate(int object_size,
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMask));
+    test(result, Immediate(kDoubleAlignmentMaskTagged));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
-    mov(Operand(result, 0),
+    mov(Operand(result, -kHeapObjectTag),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
@@ -1583,11 +1583,7 @@ void MacroAssembler::Allocate(int object_size,
   }
 
   if (top_reg.is(result)) {
-    sub(result, Immediate(object_size - kHeapObjectTag));
-  } else {
-    // Tag the result.
-    DCHECK(kHeapObjectTag == 1);
-    inc(result);
+    sub(result, Immediate(object_size));
   }
 }
 
@@ -1630,13 +1626,13 @@ void MacroAssembler::Allocate(int header_size,
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMask));
+    test(result, Immediate(kDoubleAlignmentMaskTagged));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
-    mov(Operand(result, 0),
+    mov(Operand(result, -kHeapObjectTag),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
@@ -1661,10 +1657,6 @@ void MacroAssembler::Allocate(int header_size,
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
-  // Tag result.
-  DCHECK(kHeapObjectTag == 1);
-  inc(result);
-
   UpdateAllocationTopHelper(result_end, scratch, flags);
 }
 
@@ -1703,13 +1695,13 @@ void MacroAssembler::Allocate(Register object_size,
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMask));
+    test(result, Immediate(kDoubleAlignmentMaskTagged));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
-    mov(Operand(result, 0),
+    mov(Operand(result, -kHeapObjectTag),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
@@ -1723,10 +1715,6 @@ void MacroAssembler::Allocate(Register object_size,
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
-  // Tag result.
-  DCHECK(kHeapObjectTag == 1);
-  inc(result);
-
   if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
     // The top pointer is not updated for allocation folding dominators.
     UpdateAllocationTopHelper(result_end, scratch, flags);
@@ -1742,9 +1730,9 @@ void MacroAssembler::FastAllocate(int object_size, Register result,
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMask));
+    test(result, Immediate(kDoubleAlignmentMaskTagged));
     j(zero, &aligned, Label::kNear);
-    mov(Operand(result, 0),
+    mov(Operand(result, -kHeapObjectTag),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
@@ -1752,9 +1740,6 @@ void MacroAssembler::FastAllocate(int object_size, Register result,
 
   lea(result_end, Operand(result, object_size));
   UpdateAllocationTopHelper(result_end, no_reg, flags);
-
-  DCHECK(kHeapObjectTag == 1);
-  inc(result);
 }
 
 void MacroAssembler::FastAllocate(Register object_size, Register result,
@@ -1766,9 +1751,9 @@ void MacroAssembler::FastAllocate(Register object_size, Register result,
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMask));
+    test(result, Immediate(kDoubleAlignmentMaskTagged));
     j(zero, &aligned, Label::kNear);
-    mov(Operand(result, 0),
+    mov(Operand(result, -kHeapObjectTag),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
@@ -1776,9 +1761,6 @@ void MacroAssembler::FastAllocate(Register object_size, Register result,
 
   lea(result_end, Operand(result, object_size, times_1, 0));
   UpdateAllocationTopHelper(result_end, no_reg, flags);
-
-  DCHECK(kHeapObjectTag == 1);
-  inc(result);
 }