Refactor and improve inlined double-aligned allocations

src/x64/macro-assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3740 matching lines @@
   }
 }
 
 
 void MacroAssembler::AllocateInNewSpace(int object_size,
                                         Register result,
                                         Register result_end,
                                         Register scratch,
                                         Label* gc_required,
                                         AllocationFlags flags) {
+  ASSERT((flags & (RESULT_CONTAINS_TOP | SIZE_IN_WORDS)) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       movl(result, Immediate(0x7091));
       if (result_end.is_valid()) {
         movl(result_end, Immediate(0x7191));
       }
       if (scratch.is_valid()) {
         movl(scratch, Immediate(0x7291));
       }
     }
     jmp(gc_required);
     return;
   }
   ASSERT(!result.is(result_end));
 
   // Load address of new object into result.
   LoadAllocationTopHelper(result, scratch, flags);
 
+  // Align the next allocation. Storing the filler map without checking top is
+  // always safe because the limit of the heap is always aligned.
+  if (((flags & DOUBLE_ALIGNMENT) != 0) && FLAG_debug_code) {
+    testq(result, Immediate(kDoubleAlignmentMask));
+    Check(zero, "Allocation is not double aligned");
+  }
+
   // Calculate new top and bail out if new space is exhausted.
   ExternalReference new_space_allocation_limit =
       ExternalReference::new_space_allocation_limit_address(isolate());
 
   Register top_reg = result_end.is_valid() ? result_end : result;
 
   if (!top_reg.is(result)) {
     movq(top_reg, result);
   }
   addq(top_reg, Immediate(object_size));
   j(carry, gc_required);
   Operand limit_operand = ExternalOperand(new_space_allocation_limit);
   cmpq(top_reg, limit_operand);
   j(above, gc_required);
 
   // Update allocation top.
   UpdateAllocationTopHelper(top_reg, scratch);
 
+  bool tag_result = (flags & TAG_OBJECT) != 0;
   if (top_reg.is(result)) {
-    if ((flags & TAG_OBJECT) != 0) {
+    if (tag_result) {
       subq(result, Immediate(object_size - kHeapObjectTag));
     } else {
       subq(result, Immediate(object_size));
     }
-  } else if ((flags & TAG_OBJECT) != 0) {
+  } else if (tag_result) {
     // Tag the result if requested.
-    addq(result, Immediate(kHeapObjectTag));
+    ASSERT(kHeapObjectTag == 1);
+    incq(result);
   }
 }
 
 
 void MacroAssembler::AllocateInNewSpace(int header_size,
                                         ScaleFactor element_size,
                                         Register element_count,
                                         Register result,
                                         Register result_end,
                                         Register scratch,
                                         Label* gc_required,
                                         AllocationFlags flags) {
+  ASSERT((flags & SIZE_IN_WORDS) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       movl(result, Immediate(0x7091));
       movl(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         movl(scratch, Immediate(0x7291));
       }
       // Register element_count is not modified by the function.
     }
     jmp(gc_required);
     return;
   }
   ASSERT(!result.is(result_end));
 
   // Load address of new object into result.
   LoadAllocationTopHelper(result, scratch, flags);
 
+  // Align the next allocation. Storing the filler map without checking top is
+  // always safe because the limit of the heap is always aligned.
+  if (((flags & DOUBLE_ALIGNMENT) != 0) && FLAG_debug_code) {
+    testq(result, Immediate(kDoubleAlignmentMask));
+    Check(zero, "Allocation is not double aligned");
+  }
+
   // Calculate new top and bail out if new space is exhausted.
   ExternalReference new_space_allocation_limit =
       ExternalReference::new_space_allocation_limit_address(isolate());
 
   // We assume that element_count*element_size + header_size does not
   // overflow.
   lea(result_end, Operand(element_count, element_size, header_size));
   addq(result_end, result);
   j(carry, gc_required);
   Operand limit_operand = ExternalOperand(new_space_allocation_limit);
   cmpq(result_end, limit_operand);
   j(above, gc_required);
 
   // Update allocation top.
   UpdateAllocationTopHelper(result_end, scratch);
 
   // Tag the result if requested.
   if ((flags & TAG_OBJECT) != 0) {
-    addq(result, Immediate(kHeapObjectTag));
+    ASSERT(kHeapObjectTag == 1);
+    incq(result);
   }
 }
 
 
 void MacroAssembler::AllocateInNewSpace(Register object_size,
                                         Register result,
                                         Register result_end,
                                         Register scratch,
                                         Label* gc_required,
                                         AllocationFlags flags) {
+  ASSERT((flags & (DOUBLE_ALIGNMENT | RESULT_CONTAINS_TOP |
+                   SIZE_IN_WORDS)) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       movl(result, Immediate(0x7091));
       movl(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         movl(scratch, Immediate(0x7291));
       }
       // object_size is left unchanged by this function.
     }
@@ skipping 709 matching lines @@
 
   movq(rcx, FieldOperand(rbx, Map::kPrototypeOffset));
   cmpq(rcx, null_value);
   j(not_equal, &next);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64