function.h (struct emit_status): Clarify potential contents of regno_reg_rtx array.

        * function.h (struct emit_status): Clarify potential contents
        of regno_reg_rtx array.
        * integrate.c (copy_rtx_and_substitute): Update comments.  Make
        sure entry in regno_reg_rtx is a REG before checking REG_POINTER.

Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r54924

gcc/ChangeLog

 2002-06-23  Jan Hubicka  <jh@suse.cz>
+	    Jeff Law <law@redhat.com>
+
+	* function.h (struct emit_status): Clarify potential contents
+	of regno_reg_rtx array.
+	* integrate.c (copy_rtx_and_substitute): Update comments.  Make
+	sure entry in regno_reg_rtx is a REG before checking REG_POINTER.
 
 	* reg-stack.c (convert_regs_exit): Push the registers to stack in
 	proper order.

gcc/function.h

@@ -105,7 +105,10 @@ struct emit_status GTY(())
   tree * GTY ((length ("%h.regno_pointer_align_length"))) regno_decl;
 
   /* Indexed by pseudo register number, gives the rtx for that pseudo.
-     Allocated in parallel with regno_pointer_align.  */
+     Allocated in parallel with regno_pointer_align. 
+
+     Note MEM expressions can appear in this array due to the actions
+     of put_var_into_stack.  */
   rtx * GTY ((length ("%h.regno_pointer_align_length"))) x_regno_reg_rtx;
 };
 

gcc/integrate.c

@@ -2062,7 +2062,17 @@ copy_rtx_and_substitute (orig, map, for_lhs)
 	  RTX_UNCHANGING_P (map->reg_map[regno]) = RTX_UNCHANGING_P (temp);
 	  /* A reg with REG_FUNCTION_VALUE_P true will never reach here.  */
 
-	  if (REG_POINTER (map->x_regno_reg_rtx[regno]))
+	  /* Objects may initially be represented as registers, but
+	     but turned into a MEM if their address is taken by
+	     put_var_into_stack.  Therefore, the register table may have
+	     entries which are MEMs.
+
+	     We briefly tried to clear such entries, but that ended up
+	     cascading into many changes due to the optimizers not being
+	     prepared for empty entries in the register table.  So we've
+	     decided to allow the MEMs in the register table for now.  */
+	  if (REG_P (map->x_regno_reg_rtx[regno])
+	      && REG_POINTER (map->x_regno_reg_rtx[regno]))
 	    mark_reg_pointer (map->reg_map[regno],
 			      map->regno_pointer_align[regno]);
 	  regno = REGNO (map->reg_map[regno]);