[RS6000] Correct PIC_OFFSET_TABLE_REGNUM

[Alan Modra]

Leaving this as r30 results in pic_offset_table_rtx of (reg 30)
for -m64, which is completely bogus.  Various rtl analysis predicate
functions treat pic_offset_table_rtx specially..

Bootsrapped etc.  OK to apply?

        * config/rs6000/rs6000.h (PIC_OFFSET_TABLE_REGNUM): Correct.

diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index 230ca43..9647106 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -2050,7 +2050,10 @@ do {                                                     
                     \
    to allocate such a register (if necessary).  */
 
 #define RS6000_PIC_OFFSET_TABLE_REGNUM 30
-#define PIC_OFFSET_TABLE_REGNUM (flag_pic ? RS6000_PIC_OFFSET_TABLE_REGNUM : 
INVALID_REGNUM)
+#define PIC_OFFSET_TABLE_REGNUM \
+  (TARGET_TOC ? TOC_REGISTER                   \
+   : flag_pic ? RS6000_PIC_OFFSET_TABLE_REGNUM \
+   : INVALID_REGNUM)
 
 #define TOC_REGISTER (TARGET_MINIMAL_TOC ? RS6000_PIC_OFFSET_TABLE_REGNUM : 2)
 

-- 
Alan Modra
Australia Development Lab, IBM