LCodeGen::CallKnownFunction gets the function in register.

src/arm64/lithium-codegen-arm64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ARM64_LITHIUM_CODEGEN_ARM64_H_
 #define V8_ARM64_LITHIUM_CODEGEN_ARM64_H_
 
 #include "src/arm64/lithium-arm64.h"
 
 #include "src/arm64/lithium-gap-resolver-arm64.h"
@@ skipping 300 matching lines @@
     const Runtime::Function* function = Runtime::FunctionForId(id);
     CallRuntime(function, num_arguments, instr);
   }
 
   void LoadContextFromDeferred(LOperand* context);
   void CallRuntimeFromDeferred(Runtime::FunctionId id,
                                int argc,
                                LInstruction* instr,
                                LOperand* context);
 
-  // Generate a direct call to a known function.
-  // If the function is already loaded into x1 by the caller, function_reg may
-  // be set to x1. Otherwise, it must be NoReg, and CallKnownFunction will
-  // automatically load it.
+  // Generate a direct call to a known function.  Expects the function
+  // to be in x1.
   void CallKnownFunction(Handle<JSFunction> function,
-                         int formal_parameter_count,
-                         int arity,
-                         LInstruction* instr,
-                         Register function_reg = NoReg);
+                         int formal_parameter_count, int arity,
+                         LInstruction* instr);
 
   // Support for recording safepoint and position information.
   void RecordAndWritePosition(int position) OVERRIDE;
   void RecordSafepoint(LPointerMap* pointers,
                        Safepoint::Kind kind,
                        int arguments,
                        Safepoint::DeoptMode mode);
   void RecordSafepoint(LPointerMap* pointers, Safepoint::DeoptMode mode);
   void RecordSafepoint(Safepoint::DeoptMode mode);
   void RecordSafepointWithRegisters(LPointerMap* pointers,
@@ skipping 119 matching lines @@
 
  protected:
   MacroAssembler* masm() const { return codegen_->masm(); }
 
   LCodeGen* codegen_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM64_LITHIUM_CODEGEN_ARM64_H_