rs6000: rs6000_dbx_register_number for fp/ap/mq

The frame pointer and the argument pointer aren't real registers.  MQ
was a register on old POWER.  All three are still used as arguments to
rs6000_dbx_register_number during initialisation.  If we handle them
explicitly we can do a gcc_unreachable to catch other unexpected
registers.


	* config/rs6000/rs6000.c (rs6000_dbx_register_number): Handle
	FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and 64 (which was MQ).

From-SVN: r270925

gcc/ChangeLog

+2019-05-06  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* config/rs6000/rs6000.c (rs6000_dbx_register_number): Handle
+	FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and 64 (which was MQ).
+
 2019-05-06  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/88709

gcc/config/rs6000/rs6000.c

@@ -36309,7 +36309,15 @@ rs6000_dbx_register_number (unsigned int regno, unsigned int format)
       if (regno == TEXASR_REGNO)
 	return 230;
 
-      return regno;
+      /* These do not make much sense.  */
+      if (regno == FRAME_POINTER_REGNUM)
+	return 111;
+      if (regno == ARG_POINTER_REGNUM)
+	return 67;
+      if (regno == 64)
+	return 100;
+
+      gcc_unreachable ();
 #endif
     }
 
@@ -36341,7 +36349,14 @@ rs6000_dbx_register_number (unsigned int regno, unsigned int format)
   if (regno == TEXASR_REGNO)
     return 116;
 
-  return regno;
+  if (regno == FRAME_POINTER_REGNUM)
+    return 111;
+  if (regno == ARG_POINTER_REGNUM)
+    return 67;
+  if (regno == 64)
+    return 64;
+
+  gcc_unreachable ();
 }
 
 /* target hook eh_return_filter_mode */