i386.c (ix86_maybe_switch_abi): Use named constants instead of magic numbers.

	* config/i386/i386.c (ix86_maybe_switch_abi): Use named
	constants instead of magic numbers.

From-SVN: r144706

gcc/ChangeLog

@@ -61,6 +61,7 @@
 	* config/i386/i386.c (x86_64_int_parameter_registers): Ditto.
 	(x86_64_ms_abi_int_parameter_registers): Ditto.
 	(x86_64_int_return_registers): Ditto.
+	(ix86_maybe_switch_abi): Ditto.
 	(ix86_expand_call): Ditto for clobbered_registers array.
 	(ix86_hard_regno_mode_ok): Ditto.
 	(x86_extended_QIreg_mentioned_p): Ditto.

gcc/config/i386/i386.c

@@ -4618,7 +4618,7 @@ static void
 ix86_maybe_switch_abi (void)
 {
   if (TARGET_64BIT &&
-      call_used_regs[4 /*RSI*/] ==  (cfun->machine->call_abi == MS_ABI))
+      call_used_regs[SI_REG] == (cfun->machine->call_abi == MS_ABI))
     reinit_regs ();
 }