A64: Tidy up register use in TaggedToI

src/a64/macro-assembler-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1161 matching lines @@
                       const CallWrapper& call_wrapper);
   void InvokeFunction(Handle<JSFunction> function,
                       const ParameterCount& expected,
                       const ParameterCount& actual,
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper);
 
 
   // ---- Floating point helpers ----
 
-
-  // Performs a truncating conversion of a floating point number as used by
-  // the JS bitwise operations. See ECMA-262 9.5: ToInt32. Goes to 'done' if it
-  // succeeds, otherwise falls through if result is saturated. On return
-  // 'result' either holds answer, or is clobbered on fall through.
+  // Perform a conversion from a double to a signed int64. If the input fits in
+  // range of the 64-bit result, execution branches to done. Otherwise,
+  // execution falls through, and the sign of the result can be used to
+  // determine if overflow was towards positive or negative infinity.
+  //
+  // On successful conversion, the least significant 32 bits of the result are
+  // equivalent to the ECMA-262 operation "ToInt32".
   //
   // Only public for the test code in test-code-stubs-a64.cc.
-  void TryInlineTruncateDoubleToI(Register result,
-                                  DoubleRegister input,
-                                  Label* done);
+  void TryConvertDoubleToInt64(Register result,
+                               DoubleRegister input,
+                               Label* done);
 
   // Performs a truncating conversion of a floating point number as used by
   // the JS bitwise operations. See ECMA-262 9.5: ToInt32.
   // Exits with 'result' holding the answer.
   void TruncateDoubleToI(Register result, DoubleRegister double_input);
 
   // Performs a truncating conversion of a heap number as used by
   // the JS bitwise operations. See ECMA-262 9.5: ToInt32. 'result' and 'input'
   // must be different registers.  Exits with 'result' holding the answer.
   void TruncateHeapNumberToI(Register result, Register object);
@@ skipping 1121 matching lines @@
 #error "Unsupported option"
 #define CODE_COVERAGE_STRINGIFY(x) #x
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 #endif  // V8_A64_MACRO_ASSEMBLER_A64_H_