[crankshaft] Fragmentation-free allocation folding.

src/arm64/macro-assembler-arm64.h

 // Copyright 2013 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.
 
 #ifndef V8_ARM64_MACRO_ASSEMBLER_ARM64_H_
 #define V8_ARM64_MACRO_ASSEMBLER_ARM64_H_
 
 #include <vector>
 
 #include "src/arm64/assembler-arm64.h"
@@ skipping 1294 matching lines @@
 
   // ---------------------------------------------------------------------------
   // Allocation support
 
   // Allocate an object in new space or old space. The object_size is
   // specified either in bytes or in words if the allocation flag SIZE_IN_WORDS
   // is passed. The allocated object is returned in result.
   //
   // If the new space is exhausted control continues at the gc_required label.
   // In this case, the result and scratch registers may still be clobbered.
-  // If flags includes TAG_OBJECT, the result is tagged as as a heap object.
   void Allocate(Register object_size, Register result, Register result_end,
                 Register scratch, Label* gc_required, AllocationFlags flags);
 
   void Allocate(int object_size,
                 Register result,
                 Register scratch1,
                 Register scratch2,
                 Label* gc_required,
                 AllocationFlags flags);
 
+  // FastAllocate is right now only used for folded allocations. It just
+  // increments the top pointer without checking against limit. This can only
+  // be done if it was proved earlier that the allocation will succeed.
+  void FastAllocate(Register object_size, Register result, Register result_end,
+                    Register scratch, AllocationFlags flags);
+
+  void FastAllocate(int object_size, Register result, Register scratch1,
+                    Register scratch2, AllocationFlags flags);
+
   void AllocateTwoByteString(Register result,
                              Register length,
                              Register scratch1,
                              Register scratch2,
                              Register scratch3,
                              Label* gc_required);
   void AllocateOneByteString(Register result, Register length,
                              Register scratch1, Register scratch2,
                              Register scratch3, Label* gc_required);
   void AllocateTwoByteConsString(Register result,
@@ skipping 942 matching lines @@
 #error "Unsupported option"
 #define CODE_COVERAGE_STRINGIFY(x) #x
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 #endif  // V8_ARM64_MACRO_ASSEMBLER_ARM64_H_