[turbofan] Remove access to FunctionType from call interface.

This removes the ability to directly access the {FunctionType} stored
within a {CallInterfaceDescriptor}. The field is in the process of being
deprecated and should no longer be accessed.

R=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/2191533002
Cr-Commit-Position: refs/heads/master@{#38107}

src/builtins/builtins.cc

@@ -102,7 +102,7 @@ Code* BuildWithCodeStubAssemblerCS(Isolate* isolate,
   // and this construction just queries the details from the descriptors table.
   CallInterfaceDescriptor descriptor(isolate, interface_descriptor);
   // Ensure descriptor is already initialized.
-  DCHECK_NOT_NULL(descriptor.GetFunctionType());
+  DCHECK_LE(0, descriptor.GetRegisterParameterCount());
   CodeStubAssembler assembler(isolate, &zone, descriptor, flags, name);
   generator(&assembler);
   Handle<Code> code = assembler.GenerateCode();

src/interface-descriptors.h

@@ -133,8 +133,6 @@ class CallInterfaceDescriptorData {
     return platform_specific_descriptor_;
   }
 
-  FunctionType* function_type() const { return function_type_; }
-
  private:
   int register_param_count_;
 
@@ -179,7 +177,7 @@ class CallInterfaceDescriptor {
   }
 
   int GetStackParameterCount() const {
-    return data()->function_type()->Arity() - data()->register_param_count();
+    return data()->param_count() - data()->register_param_count();
   }
 
   Register GetRegisterParameter(int index) const {
@@ -196,8 +194,6 @@ class CallInterfaceDescriptor {
     return data()->platform_specific_descriptor();
   }
 
-  FunctionType* GetFunctionType() const { return data()->function_type(); }
-
   static const Register ContextRegister();
 
   const char* DebugName(Isolate* isolate) const;