Commit: RX: Predicate return pattern

Commit: RX: Predicate return pattern

[Nick Clifton]

Hi Guys,

  As pointed out by Richard Henderson the new return pattern in the RX
  backend should only be used when it is possible to return with just a
  simple RTS instruction, so I am checking in the patch below to
  implement this.

Cheers
  Nick

gcc/ChangeLog
2012-01-17  Nick Clifton  <nickc@redhat.com>

	* config/rx/rx.c (rx_can_use_simple_return): New function.
	* config/rx/rx-protos.h (rx_can_use_simple_return): Prototype.
	* config/rx/rx.md (return): Predicate on rx_can_use_simple_return.

Index: gcc/config/rx/rx-protos.h
===================================================================
--- gcc/config/rx/rx-protos.h	(revision 183234)
+++ gcc/config/rx/rx-protos.h	(working copy)
@@ -21,6 +22,8 @@
 #ifndef GCC_RX_PROTOS_H
 #define GCC_RX_PROTOS_H
 
+extern bool             rx_can_use_simple_return (void);
+extern void		rx_expand_epilogue (bool);
 extern void		rx_expand_prologue (void);
 extern int		rx_initial_elimination_offset (int, int);
 
@@ -29,7 +32,6 @@
 extern int 		rx_align_for_label (rtx, int);
 extern void             rx_emit_stack_popm (rtx *, bool);
 extern void             rx_emit_stack_pushm (rtx *);
-extern void		rx_expand_epilogue (bool);
 extern char *		rx_gen_move_template (rtx *, bool);
 extern bool		rx_is_legitimate_constant (enum machine_mode, rtx);
 extern bool		rx_is_restricted_memory_address (rtx,
Index: gcc/config/rx/rx.md
===================================================================
--- gcc/config/rx/rx.md	(revision 183234)
+++ gcc/config/rx/rx.md	(working copy)
@@ -342,7 +343,7 @@
 
 (define_expand "return"
   [(return)]
-  ""
+  "rx_can_use_simple_return ()"
   "rx_expand_epilogue (false); DONE;"
 )
 
Index: gcc/config/rx/rx.c
===================================================================
--- gcc/config/rx/rx.c	(revision 183234)
+++ gcc/config/rx/rx.c	(working copy)
@@ -1818,7 +1819,31 @@
 
   return vector;
 }
-  
+
+/* Returns true if a simple return insn can be used.  */
+
+bool
+rx_can_use_simple_return (void)
+{
+  unsigned int low;
+  unsigned int high;
+  unsigned int frame_size;
+  unsigned int stack_size;
+  unsigned int register_mask;
+
+  if (is_naked_func (NULL_TREE)
+      || is_fast_interrupt_func (NULL_TREE)
+      || is_interrupt_func (NULL_TREE))
+    return false;
+
+  rx_get_stack_layout (& low, & high, & register_mask,
+		       & frame_size, & stack_size);
+
+  return (register_mask == 0
+	  && (frame_size + stack_size) == 0
+	  && low == 0);
+}
+
 void
 rx_expand_epilogue (bool is_sibcall)
 {