[PATCH] fix for web pass

[Roman Zippel]

Hi,

The patch below fixes a problem in the web pass fixes. The 960416-1 test 
case produces a instruction like this for m68k:

(insn 30 28 31 3 (parallel [
            (set (subreg:SI (reg:DI 48) 4)
                (mult:SI (reg/v:SI 41 [ ad ])
                    (reg/v:SI 42 [ bd ])))
            (set (subreg:SI (reg:DI 48) 0)
                (truncate:SI (lshiftrt:DI (mult:DI (zero_extend:DI (reg/v:SI 41 [ ad ]))
                            (zero_extend:DI (reg/v:SI 42 [ bd ])))
                        (const_int 32 [0x20]))))
        ]) 130 {*m68k.md:2527} (nil)
    (nil))

Data flow analysis finds two defs for the two sets here, but union_defs 
uses only one of it to create a union. The result is that the web pass 
thinks the two uses of (reg 48) are independent and replaces one of it 
with a new register.
The patch is tested on m68k-linux and i586-linux.

bye, Roman

2004-06-05  Roman Zippel <zippel@linux-m68k.org>

	* web.c (union_defs): use all defs of an instruction to create a 
	union with a read/write use


Index: web.c
===================================================================
RCS file: /cvsroot/gcc/gcc/gcc/web.c,v
retrieving revision 2.9
diff -u -r2.9 web.c
--- web.c	15 May 2004 09:39:29 -0000	2.9
+++ web.c	26 May 2004 23:43:36 -0000
@@ -160,11 +160,13 @@
     {
       struct df_link *link = DF_INSN_DEFS (df, DF_REF_INSN (use));
 
-      while (DF_REF_REAL_REG (link->ref) != DF_REF_REAL_REG (use))
-	link = link->next;
-
-      unionfind_union (use_entry + DF_REF_ID (use),
-		       def_entry + DF_REF_ID (link->ref));
+      while (link)
+	{
+	  if (DF_REF_REAL_REG (link->ref) == DF_REF_REAL_REG (use))
+	    unionfind_union (use_entry + DF_REF_ID (use),
+			     def_entry + DF_REF_ID (link->ref));
+	  link = link->next;
+	}
     }
 }