[crankshaft] Fragmentation-free allocation folding.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 223e4647a11d39ba38f8e81c8cb2cc9062aa34eb..013d0f13b5dc391e6f08e78dac277a27a2ee88cd 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -1307,6 +1307,15 @@ class MacroAssembler: public Assembler {
                 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. Returns
   // tagged pointer in result register, or jumps to gc_required if new
   // space is full.