[turbofan] Initial version of allocation folding and write barrier elimination.

src/arm64/builtins-arm64.cc

Index: src/arm64/builtins-arm64.cc
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index d4b76046562abfa32422d074a2503ec54d3eec2a..3f0a070df97b9ba25a519b68e37834216d2dbd46 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -2758,11 +2758,6 @@ void Builtins::Generate_AllocateInNewSpace(MacroAssembler* masm) {
   //  -- x1 : requested object size (untagged)
   //  -- lr : return address
   // -----------------------------------
-  Label runtime;
-  __ Allocate(x1, x0, x2, x3, &runtime, NO_ALLOCATION_FLAGS);
-  __ Ret();
-
-  __ Bind(&runtime);
   __ SmiTag(x1);
   __ Push(x1);
   __ Move(cp, Smi::FromInt(0));
@@ -2776,11 +2771,6 @@ void Builtins::Generate_AllocateInOldSpace(MacroAssembler* masm) {
   //  -- x1 : requested object size (untagged)
   //  -- lr : return address
   // -----------------------------------
-  Label runtime;
-  __ Allocate(x1, x0, x2, x3, &runtime, PRETENURE);
-  __ Ret();
-
-  __ Bind(&runtime);
   __ SmiTag(x1);
   __ Move(x2, Smi::FromInt(AllocateTargetSpace::encode(OLD_SPACE)));
   __ Push(x1, x2);