rs6000.h (RETURN_ADDR_RTX): Add definition to support __builtin_return_address…

rs6000.h (RETURN_ADDR_RTX): Add definition to support __builtin_return_address and __builtin_frame_address...

        * rs6000.h/rs6000.h (RETURN_ADDR_RTX): Add definition to support
        __builtin_return_address and __builtin_frame_address on the
        rs6000.  This is necessary to support exception handling in g++ on
        the rs6000.
Fixes eh6.C on rs6000.

From-SVN: r9054

gcc/config/rs6000/rs6000.h

@@ -1151,6 +1151,27 @@ struct rs6000_args {int words, fregno, nargs_prototype; };
 		  force_reg (SImode, (CXT)));			\
 }
 
+/* Definitions for __builtin_return_address and __builtin_frame_address.
+   __builtin_return_address (0) should give link register (65), enable
+   this. */
+/* This should be uncommented, so that the link register is used, but
+   currently this would result in unmatched insns and spilling fixed
+   registers so we'll leave it for another day.  When these problems are
+   taken care of one additional fetch will be necessary in RETURN_ADDR_RTX.
+   (mrs) */
+/* #define RETURN_ADDR_IN_PREVIOUS_FRAME */
+/* The current return address is in link register (65).  The return address
+   of anything farther back is accessed normally at an offset of 8 from the
+   frame pointer.  */
+#define RETURN_ADDR_RTX(count, frame)			\
+  ((count == -1)					\
+   ? gen_rtx (REG, Pmode, 65)				\
+   : copy_to_reg (gen_rtx (MEM, Pmode,			\
+			   memory_address (Pmode, 	\
+					   plus_constant (copy_to_reg (gen_rtx (MEM, Pmode, \
+										memory_address (Pmode, frame))), \
+							  8)))))
+
 /* Definitions for register eliminations.
 
    We have two registers that can be eliminated on the RS/6000.  First, the