Refactor and improve inlined double-aligned allocations

src/ia32/macro-assembler-ia32.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 1223 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.
       mov(result, Immediate(0x7091));
       if (result_end.is_valid()) {
         mov(result_end, Immediate(0x7191));
       }
       if (scratch.is_valid()) {
         mov(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) {

[Yang, 2012/12/28 10:03:48]

Maybe add an assert saying that this works because kPointerAlignment * 2 ==
kDoubleAlignment

[danno, 2012/12/28 15:44:55]

Done.

+    Label aligned;
+    test(result, Immediate(kDoubleAlignmentMask));
+    j(zero, &aligned, Label::kNear);
+    mov(Operand(result, 0),
+        Immediate(isolate()->factory()->one_pointer_filler_map()));
+    add(result, Immediate(kDoubleSize / 2));
+    bind(&aligned);
+  }
+
   Register top_reg = result_end.is_valid() ? result_end : result;
 
   // Calculate new top and bail out if new space is exhausted.
   ExternalReference new_space_allocation_limit =
       ExternalReference::new_space_allocation_limit_address(isolate());
 
   if (!top_reg.is(result)) {
     mov(top_reg, result);
   }
   add(top_reg, Immediate(object_size));
   j(carry, gc_required);
   cmp(top_reg, Operand::StaticVariable(new_space_allocation_limit));
   j(above, gc_required);
 
   // Update allocation top.
   UpdateAllocationTopHelper(top_reg, scratch);
 
   // Tag result if requested.
+  bool tag_result = (flags & TAG_OBJECT) != 0;
   if (top_reg.is(result)) {
-    if ((flags & TAG_OBJECT) != 0) {
+    if (tag_result) {
       sub(result, Immediate(object_size - kHeapObjectTag));
     } else {
       sub(result, Immediate(object_size));
     }
-  } else if ((flags & TAG_OBJECT) != 0) {
-    add(result, Immediate(kHeapObjectTag));
+  } else if (tag_result) {
+    ASSERT(kHeapObjectTag == 1);
+    inc(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) {
+void MacroAssembler::AllocateInNewSpace(
+    int header_size,
+    ScaleFactor element_size,
+    Register element_count,
+    RegisterValueType element_count_type,
+    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.
       mov(result, Immediate(0x7091));
       mov(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         mov(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) {
+    Label aligned;
+    test(result, Immediate(kDoubleAlignmentMask));
+    j(zero, &aligned, Label::kNear);
+    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 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.
+  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);

[Yang, 2012/12/28 10:03:48]

Also assert that kSmiTagSize == 1.

[danno, 2012/12/28 15:44:55]

Done.

+    ASSERT(element_size >= times_2);
+    element_size = static_cast<ScaleFactor>(element_size - 1);
+  } else {
+    ASSERT(element_count_type == REGISTER_VALUE_IS_INT32);
+  }
   lea(result_end, Operand(element_count, element_size, header_size));
   add(result_end, result);
   j(carry, gc_required);
   cmp(result_end, Operand::StaticVariable(new_space_allocation_limit));
   j(above, gc_required);
 
-  // Tag result if requested.
   if ((flags & TAG_OBJECT) != 0) {
-    lea(result, Operand(result, kHeapObjectTag));
+    ASSERT(kHeapObjectTag == 1);
+    inc(result);
   }
 
   // Update allocation top.
   UpdateAllocationTopHelper(result_end, scratch);
 }
 
 
 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.
       mov(result, Immediate(0x7091));
       mov(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         mov(scratch, Immediate(0x7291));
       }
       // object_size is left unchanged by this function.
     }
@@ skipping 69 matching lines @@
   ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) == 0);
   ASSERT(kShortSize == 2);
   // scratch1 = length * 2 + kObjectAlignmentMask.
   lea(scratch1, Operand(length, length, times_1, kObjectAlignmentMask));
   and_(scratch1, Immediate(~kObjectAlignmentMask));
 
   // Allocate two byte string in new space.
   AllocateInNewSpace(SeqTwoByteString::kHeaderSize,
                      times_1,
                      scratch1,
+                     REGISTER_VALUE_IS_INT32,
                      result,
                      scratch2,
                      scratch3,
                      gc_required,
                      TAG_OBJECT);
 
   // Set the map, length and hash field.
   mov(FieldOperand(result, HeapObject::kMapOffset),
       Immediate(isolate()->factory()->string_map()));
   mov(scratch1, length);
@@ skipping 15 matching lines @@
   ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) == 0);
   mov(scratch1, length);
   ASSERT(kCharSize == 1);
   add(scratch1, Immediate(kObjectAlignmentMask));
   and_(scratch1, Immediate(~kObjectAlignmentMask));
 
   // Allocate ASCII string in new space.
   AllocateInNewSpace(SeqOneByteString::kHeaderSize,
                      times_1,
                      scratch1,
+                     REGISTER_VALUE_IS_INT32,
                      result,
                      scratch2,
                      scratch3,
                      gc_required,
                      TAG_OBJECT);
 
   // Set the map, length and hash field.
   mov(FieldOperand(result, HeapObject::kMapOffset),
       Immediate(isolate()->factory()->ascii_string_map()));
   mov(scratch1, length);
@@ skipping 1520 matching lines @@
   j(not_equal, call_runtime);
 
   mov(ecx, FieldOperand(ebx, Map::kPrototypeOffset));
   cmp(ecx, isolate()->factory()->null_value());
   j(not_equal, &next);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32