[RFC] Fix context-sensitiveness of peephole2 pass

[Eric Botcazou]

As discovered by Richard B. under PR rtl-optimization/58831, the peephole2 
pass has been context-sensitive for a long time when scratch registers are 
needed, in the sense that the behaviour of the pass for a given function is 
dependent on what happened for the previously optimized function.

Obvious patch attached, tested on x86_64-suse-linux.  Do we want to apply it 
on mainline only or on all the active branches?


2013-10-24  Eric Botcazou  <ebotca...@adacore.com>

        * recog.c (search_ofs): New static variable moved from...
        (peep2_find_free_register): ...here.
        (peephole2_optimize): Initialize it.


-- 
Eric Botcazou
Index: recog.c
===================================================================
--- recog.c	(revision 203876)
+++ recog.c	(working copy)
@@ -3068,6 +3068,9 @@ peep2_reg_dead_p (int ofs, rtx reg)
   return 1;
 }
 
+/* Regno offset to be used in the register search.  */
+static int search_ofs;
+
 /* Try to find a hard register of mode MODE, matching the register class in
    CLASS_STR, which is available at the beginning of insn CURRENT_INSN and
    remains available until the end of LAST_INSN.  LAST_INSN may be NULL_RTX,
@@ -3083,7 +3086,6 @@ rtx
 peep2_find_free_register (int from, int to, const char *class_str,
 			  enum machine_mode mode, HARD_REG_SET *reg_set)
 {
-  static int search_ofs;
   enum reg_class cl;
   HARD_REG_SET live;
   df_ref *def_rec;
@@ -3548,6 +3550,7 @@ peephole2_optimize (void)
   /* Initialize the regsets we're going to use.  */
   for (i = 0; i < MAX_INSNS_PER_PEEP2 + 1; ++i)
     peep2_insn_data[i].live_before = BITMAP_ALLOC (&reg_obstack);
+  search_ofs = 0;
   live = BITMAP_ALLOC (&reg_obstack);
 
   FOR_EACH_BB_REVERSE (bb)