Revert of Provide a tagged allocation top pointer.

src/ia32/macro-assembler-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 1486 matching lines @@
     mov(result, Operand(scratch, 0));
   }
 }
 
 
 void MacroAssembler::UpdateAllocationTopHelper(Register result_end,
                                                Register scratch,
                                                AllocationFlags flags) {
   if (emit_debug_code()) {
     test(result_end, Immediate(kObjectAlignmentMask));
-    Check(not_zero, kUnalignedAllocationInNewSpace);
+    Check(zero, kUnalignedAllocationInNewSpace);
   }
 
   ExternalReference allocation_top =
       AllocationUtils::GetAllocationTopReference(isolate(), flags);
 
   // Update new top. Use scratch if available.
   if (scratch.is(no_reg)) {
     mov(Operand::StaticVariable(allocation_top), result_end);
   } else {
     mov(Operand(scratch, 0), result_end);
@@ skipping 30 matching lines @@
   LoadAllocationTopHelper(result, scratch, flags);
 
   ExternalReference allocation_limit =
       AllocationUtils::GetAllocationLimitReference(isolate(), flags);
 
   // 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.
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMaskTagged));
+    test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
     mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   // Calculate new top and bail out if space is exhausted.
   Register top_reg = result_end.is_valid() ? result_end : result;
 
   if (!top_reg.is(result)) {
     mov(top_reg, result);
   }
   add(top_reg, Immediate(object_size));
   cmp(top_reg, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
   if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
     // The top pointer is not updated for allocation folding dominators.
     UpdateAllocationTopHelper(top_reg, scratch, flags);
   }
 
   if (top_reg.is(result)) {
-    sub(result, Immediate(object_size));
+    sub(result, Immediate(object_size - kHeapObjectTag));
+  } else {
+    // Tag the result.
+    DCHECK(kHeapObjectTag == 1);
+    inc(result);
   }
 }
 
 
 void MacroAssembler::Allocate(int header_size,
                               ScaleFactor element_size,
                               Register element_count,
                               RegisterValueType element_count_type,
                               Register result,
                               Register result_end,
@@ skipping 22 matching lines @@
   LoadAllocationTopHelper(result, scratch, flags);
 
   ExternalReference allocation_limit =
       AllocationUtils::GetAllocationLimitReference(isolate(), flags);
 
   // 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.
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMaskTagged));
+    test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
-    mov(Operand(result, -kHeapObjectTag),
+    mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   // Calculate new top and bail out if space is exhausted.
   // We assume that element_count*element_size + header_size does not
   // overflow.
   if (element_count_type == REGISTER_VALUE_IS_SMI) {
     STATIC_ASSERT(static_cast<ScaleFactor>(times_2 - 1) == times_1);
     STATIC_ASSERT(static_cast<ScaleFactor>(times_4 - 1) == times_2);
     STATIC_ASSERT(static_cast<ScaleFactor>(times_8 - 1) == times_4);
     DCHECK(element_size >= times_2);
     DCHECK(kSmiTagSize == 1);
     element_size = static_cast<ScaleFactor>(element_size - 1);
   } else {
     DCHECK(element_count_type == REGISTER_VALUE_IS_INT32);
   }
 
   lea(result_end, Operand(element_count, element_size, header_size));
   add(result_end, result);
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
+  // Tag result.
+  DCHECK(kHeapObjectTag == 1);
+  inc(result);
+
   UpdateAllocationTopHelper(result_end, scratch, flags);
 }
 
 
 void MacroAssembler::Allocate(Register object_size,
                               Register result,
                               Register result_end,
                               Register scratch,
                               Label* gc_required,
                               AllocationFlags flags) {
@@ skipping 18 matching lines @@
   LoadAllocationTopHelper(result, scratch, flags);
 
   ExternalReference allocation_limit =
       AllocationUtils::GetAllocationLimitReference(isolate(), flags);
 
   // 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.
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMaskTagged));
+    test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
     if ((flags & PRETENURE) != 0) {
       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
-    mov(Operand(result, -kHeapObjectTag),
+    mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   // Calculate new top and bail out if space is exhausted.
   if (!object_size.is(result_end)) {
     mov(result_end, object_size);
   }
   add(result_end, result);
   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);
   }
 }
 
 void MacroAssembler::FastAllocate(int object_size, Register result,
                                   Register result_end, AllocationFlags flags) {
   DCHECK(!result.is(result_end));
   // Load address of new object into result.
   LoadAllocationTopHelper(result, no_reg, flags);
 
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMaskTagged));
+    test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
-    mov(Operand(result, -kHeapObjectTag),
+    mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   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,
                                   Register result_end, AllocationFlags flags) {
   DCHECK(!result.is(result_end));
   // Load address of new object into result.
   LoadAllocationTopHelper(result, no_reg, flags);
 
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
-    test(result, Immediate(kDoubleAlignmentMaskTagged));
+    test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
-    mov(Operand(result, -kHeapObjectTag),
+    mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   lea(result_end, Operand(result, object_size, times_1, 0));
   UpdateAllocationTopHelper(result_end, no_reg, flags);
+
+  DCHECK(kHeapObjectTag == 1);
+  inc(result);
 }
 
 
 void MacroAssembler::AllocateHeapNumber(Register result,
                                         Register scratch1,
                                         Register scratch2,
                                         Label* gc_required,
                                         MutableMode mode) {
   // Allocate heap number in new space.
   Allocate(HeapNumber::kSize, result, scratch1, scratch2, gc_required,
@@ skipping 1663 matching lines @@
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32