Handle PROCESSOR_IAMCU in ix86_target_macros_internal

Define __i586__/__pentium__ for -march=iamcu and __tune_iamcu__ for
-mtune=iamcu.

	* config/i386/i386-c.c (ix86_target_macros_internal): Handle
	PROCESSOR_IAMCU.

From-SVN: r225471

gcc/config/i386/i386-c.c

@@ -64,6 +64,8 @@ ix86_target_macros_internal (HOST_WIDE_INT isa_flag,
       def_or_undef (parse_in, "__i486");
       def_or_undef (parse_in, "__i486__");
       break;
+    case PROCESSOR_IAMCU:
+      /* Intel MCU is based on Intel Pentium CPU.  */
     case PROCESSOR_PENTIUM:
       def_or_undef (parse_in, "__i586");
       def_or_undef (parse_in, "__i586__");
@@ -285,6 +287,9 @@ ix86_target_macros_internal (HOST_WIDE_INT isa_flag,
     case PROCESSOR_KNL:
       def_or_undef (parse_in, "__tune_knl__");
       break;
+    case PROCESSOR_IAMCU:
+      def_or_undef (parse_in, "__tune_iamcu__");
+      break;
     case PROCESSOR_INTEL:
     case PROCESSOR_GENERIC:
       break;