[ARC] Disable TP register when building for bare metal.

gcc/
2017-03-27  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/elf.h (ARGET_ARC_TP_REGNO_DEFAULT): Define.
	* config/arc/linux.h (ARGET_ARC_TP_REGNO_DEFAULT): Likewise.
	* config/arc/arc.opt (mtp-regno): Use ARGET_ARC_TP_REGNO_DEFAULT.

From-SVN: r246497

gcc/ChangeLog

 2017-03-27  Claudiu Zissulescu  <claziss@synopsys.com>
 
+	* config/arc/elf.h (ARGET_ARC_TP_REGNO_DEFAULT): Define.
+	* config/arc/linux.h (ARGET_ARC_TP_REGNO_DEFAULT): Likewise.
+	* config/arc/arc.opt (mtp-regno): Use ARGET_ARC_TP_REGNO_DEFAULT.
+
+2017-03-27  Claudiu Zissulescu  <claziss@synopsys.com>
+
 	* config/arc/predicates.md (long_immediate_loadstore_operand):
 	Consider scaled addresses cases.
 

gcc/config/arc/arc.opt

@@ -469,7 +469,7 @@ EnumValue
 Enum(arc_fpu) String(fpud_all) Value(FPU_FPUD_ALL)
 
 mtp-regno=
-Target RejectNegative Joined UInteger Var(arc_tp_regno) Init(25)
+Target RejectNegative Joined UInteger Var(arc_tp_regno) Init(TARGET_ARC_TP_REGNO_DEFAULT)
 Specify thread pointer register number.
 
 mtp-regno=none

gcc/config/arc/elf.h

@@ -53,3 +53,7 @@ along with GCC; see the file COPYING3.  If not see
 #  define MULTILIB_DEFAULTS { "mcpu=" ARC_MULTILIB_CPU_DEFAULT }
 # endif
 #endif
+
+/* Bare-metal toolchains do not need a thread pointer register.  */
+#undef TARGET_ARC_TP_REGNO_DEFAULT
+#define TARGET_ARC_TP_REGNO_DEFAULT -1

gcc/config/arc/linux.h

@@ -74,3 +74,7 @@ along with GCC; see the file COPYING3.  If not see
 /* We do not have any MULTILIB_OPTIONS specified, so there are no
    MULTILIB_DEFAULTS.  */
 #undef  MULTILIB_DEFAULTS
+
+/* Linux toolchains use r25 as the thread pointer register.  */
+#undef TARGET_ARC_TP_REGNO_DEFAULT
+#define TARGET_ARC_TP_REGNO_DEFAULT 25