X87: [crankshaft] Fragmentation-free allocation folding.

src/x87/macro-assembler-x87.h

 // 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.
 
 #ifndef V8_X87_MACRO_ASSEMBLER_X87_H_
 #define V8_X87_MACRO_ASSEMBLER_X87_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/frames.h"
@@ skipping 611 matching lines @@
                 Register scratch, Label* gc_required, AllocationFlags flags);
 
   void Allocate(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);
 
   void Allocate(Register object_size, Register result, Register result_end,
                 Register scratch, 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(int object_size, Register result, Register result_end,
                     AllocationFlags flags);
   void FastAllocate(Register object_size, Register result, Register result_end,
                     AllocationFlags flags);
 
   // Allocate a heap number in new space with undefined value. The
   // register scratch2 can be passed as no_reg; the others must be
   // valid registers. Returns tagged pointer in result register, or
   // jumps to gc_required if new space is full.
   void AllocateHeapNumber(Register result, Register scratch1, Register scratch2,
@@ skipping 408 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_X87_MACRO_ASSEMBLER_X87_H_