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

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 5d7354a6515c3be3e2e3230ca07ea514954238c5..4834e70ed9544a96cf855da4987f552938ced426 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -462,17 +462,6 @@ void AllocateHeapNumberStub::GenerateAssembly(
   assembler->Return(result);
 }
 
-void AllocateMutableHeapNumberStub::GenerateAssembly(
-    CodeStubAssembler* assembler) const {
-  typedef compiler::Node Node;
-
-  Node* result = assembler->Allocate(HeapNumber::kSize);
-  assembler->StoreMapNoWriteBarrier(
-      result,
-      assembler->HeapConstant(isolate()->factory()->mutable_heap_number_map()));
-  assembler->Return(result);
-}
-
 #define SIMD128_GEN_ASM(TYPE, Type, type, lane_count, lane_type)            \
   void Allocate##Type##Stub::GenerateAssembly(CodeStubAssembler* assembler) \
       const {                                                               \
@@ -4042,11 +4031,6 @@ void AllocateHeapNumberStub::InitializeDescriptor(
 }
 
 
-void AllocateMutableHeapNumberStub::InitializeDescriptor(
-    CodeStubDescriptor* descriptor) {
-  descriptor->Initialize();
-}
-
 #define SIMD128_INIT_DESC(TYPE, Type, type, lane_count, lane_type) \
   void Allocate##Type##Stub::InitializeDescriptor(                 \
       CodeStubDescriptor* descriptor) {                            \