i386.c (ix86_reorg): Replace the jump instead of adding nop.

	* i386.c (ix86_reorg): Replace the jump instead of adding nop.
	* i386.md (UNSPEC_REP): New constant.
	(return_internal_long): New pattern.

From-SVN: r67432

gcc/ChangeLog

+Wed Jun  4 09:49:21 CEST 2003  Jan Hubicka  <jh@suse.cz>
+
+	* i386.c (ix86_reorg): Replace the jump instead of adding nop.
+	* i386.md (UNSPEC_REP): New constant.
+	(return_internal_long): New pattern.
+
 2003-06-04  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	PR optimization/11018

gcc/config/i386/i386.c

@@ -15543,9 +15543,10 @@ ix86_reorg ()
     basic_block bb = e->src;
     rtx ret = bb->end;
     rtx prev;
-    bool insert = false;
+    bool replace = false;
 
-    if (!returnjump_p (ret) || !maybe_hot_bb_p (bb))
+    if (GET_CODE (ret) != JUMP_INSN || GET_CODE (PATTERN (ret)) != RETURN
+	|| !maybe_hot_bb_p (bb))
       continue;
     for (prev = PREV_INSN (ret); prev; prev = PREV_INSN (prev))
       if (active_insn_p (prev) || GET_CODE (prev) == CODE_LABEL)
@@ -15556,22 +15557,25 @@ ix86_reorg ()
 	for (e = bb->pred; e; e = e->pred_next)
 	  if (EDGE_FREQUENCY (e) && e->src->index >= 0
 	      && !(e->flags & EDGE_FALLTHRU))
-	    insert = 1;
+	    replace = true;
       }
-    if (!insert)
+    if (!replace)
       {
 	prev = prev_active_insn (ret);
 	if (prev
 	    && ((GET_CODE (prev) == JUMP_INSN && any_condjump_p (prev))
 		|| GET_CODE (prev) == CALL_INSN))
-	  insert = 1;
+	  replace = true;
 	/* Empty functions get branch misspredict even when the jump destination
 	   is not visible to us.  */
 	if (!prev && cfun->function_frequency > FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)
-	  insert = 1;
+	  replace = true;
+      }
+    if (replace)
+      {
+        emit_insn_before (gen_return_internal_long (), ret);
+	delete_insn (ret);
       }
-    if (insert)
-      emit_insn_before (gen_nop (), ret);
   }
 }
 

gcc/config/i386/i386.md

@@ -113,6 +113,9 @@
    ; x87 Floating point
    (UNSPEC_FPATAN		65)
    (UNSPEC_FYL2X		66)
+
+   ; REP instruction
+   (UNSPEC_REP			67)
   ])
 
 (define_constants
@@ -14236,6 +14239,19 @@
    (set_attr "length_immediate" "0")
    (set_attr "modrm" "0")])
 
+;; Used by x86_machine_dependent_reorg to avoid penalty on single byte RET
+;; instruction Athlon and K8 have.
+
+(define_insn "return_internal_long"
+  [(return)
+   (unspec [(const_int 0)] UNSPEC_REP)]
+  "reload_completed"
+  "rep {;} ret"
+  [(set_attr "length" "1")
+   (set_attr "length_immediate" "0")
+   (set_attr "prefix_rep" "1")
+   (set_attr "modrm" "0")])
+
 (define_insn "return_pop_internal"
   [(return)
    (use (match_operand:SI 0 "const_int_operand" ""))]