powerpc: Use global register variable in <thread_pointer.h>

A local register variable is merely a compiler hint, and so not
appropriate in this context.  Move the global register variable into
<thread_pointer.h> and include it from <tls.h>, as there can only
be one global definition for one particular register.

Fixes commit 8dbeb0561e
("nptl: Add <thread_pointer.h> for defining __thread_pointer").

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>

sysdeps/powerpc/nptl/thread_pointer.h

@@ -19,15 +19,16 @@
 #ifndef _SYS_THREAD_POINTER_H
 #define _SYS_THREAD_POINTER_H
 
+#ifdef __powerpc64__
+register void *__thread_register asm ("r13");
+#else
+register void *__thread_register asm ("r2");
+#endif
+
 static inline void *
 __thread_pointer (void)
 {
-#ifdef __powerpc64__
-  register void *__result asm ("r13");
-#else
-  register void *__result asm ("r2");
-#endif
-  return __result;
+  return __thread_register;
 }
 
 #endif /* _SYS_THREAD_POINTER_H */

sysdeps/powerpc/nptl/tls.h

@@ -26,6 +26,7 @@
 # include <stddef.h>
 # include <stdint.h>
 # include <dl-dtv.h>
+# include <thread_pointer.h>
 
 #else /* __ASSEMBLER__ */
 # include <tcb-offsets.h>
@@ -36,16 +37,10 @@
 #ifndef __powerpc64__
 /* Register r2 (tp) is reserved by the ABI as "thread pointer". */
 # define PT_THREAD_POINTER PT_R2
-# ifndef __ASSEMBLER__
-register void *__thread_register __asm__ ("r2");
-# endif
 
 #else /* __powerpc64__ */
 /* Register r13 (tp) is reserved by the ABI as "thread pointer". */
 # define PT_THREAD_POINTER PT_R13
-# ifndef __ASSEMBLER__
-register void *__thread_register __asm__ ("r13");
-# endif
 #endif /* __powerpc64__ */
 
 #ifndef __ASSEMBLER__