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

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index c44297c9685b893dc1a15e0fd14a0fb300316540..4159ed455b27844576170a84d044560f9b857be7 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -47,7 +47,6 @@ class PlatformInterfaceDescriptor;
   V(RegExpConstructResult)                    \
   V(TransitionElementsKind)                   \
   V(AllocateHeapNumber)                       \
-  V(AllocateMutableHeapNumber)                \
   V(AllocateFloat32x4)                        \
   V(AllocateInt32x4)                          \
   V(AllocateUint32x4)                         \
@@ -582,12 +581,6 @@ class AllocateHeapNumberDescriptor : public CallInterfaceDescriptor {
 SIMD128_TYPES(SIMD128_ALLOC_DESC)
 #undef SIMD128_ALLOC_DESC
 
-class AllocateMutableHeapNumberDescriptor : public CallInterfaceDescriptor {
- public:
-  DECLARE_DESCRIPTOR(AllocateMutableHeapNumberDescriptor,
-                     CallInterfaceDescriptor)
-};
-
 class ArrayNoArgumentConstructorDescriptor : public CallInterfaceDescriptor {
  public:
   DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(