re PR target/34888 (Stack patterns for AVR not optimal)

PR target/34888
        * config/avr/avr.md: New splitter for REG_ARGS_SIZE 0.

From-SVN: r177300

gcc/ChangeLog

+2011-08-03  Richard Henderson  <rth@redhat.com>
+
+	PR target/34888
+	* config/avr/avr.md: New splitter for REG_ARGS_SIZE 0.
+
 2011-08-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/49948

gcc/config/avr/avr.md

@@ -235,6 +235,17 @@
   DONE;
 })
 
+;; Notice a special-case when adding N to SP where N results in a
+;; zero REG_ARGS_SIZE.  This is equivalent to a move from FP.
+(define_split
+  [(set (reg:HI REG_SP) (match_operand:HI 0 "register_operand" ""))]
+  "reload_completed
+   && frame_pointer_needed
+   && !cfun->calls_alloca
+   && find_reg_note (insn, REG_ARGS_SIZE, const0_rtx)"
+  [(set (reg:HI REG_SP) (reg:HI REG_Y))]
+  "")
+
 ;;========================================================================
 ;; move byte
 ;; The last alternative (any immediate constant to any register) is