Followup fix for auto-inc-dec.c, PR44404

[Bernd Schmidt <bernds at codesourcery dot com>]

Kazu recently made a change in auto-inc-dec.c to avoid using
count_occurrences in one case, since it doesn't handle hard registers
correctly.

There was a patch posted at
  http://gcc.gnu.org/ml/gcc-patches/2010-06/msg00514.html

which looks correct, but a different patch was checked in:

@@ -1068,6 +1068,13 @@ find_inc (bool first_try)
       /* For the post_add to work, the result_reg of the inc must not be
 	 used in the mem insn since this will become the new index
 	 register.  */
+      if (count_occurrences (PATTERN (mem_insn.insn), inc_insn.reg_res,
1) == 0
+	  && reg_overlap_mentioned_p (inc_insn.reg_res, PATTERN (mem_insn.insn)))
+	{
+	  debug_rtx (mem_insn.insn);
+	  debug_rtx (inc_insn.reg_res);
+	  gcc_unreachable ();
+	}
       if (count_occurrences (PATTERN (mem_insn.insn), inc_insn.reg_res,
1) != 0)
 	{
 	  if (dump_file)

which isn't actually fixing anything, just causing an abort when we
encounter the problematic situation.  This triggers on the PR44404
testcase if my ARM ldm/stm peephole patch is applied.

I'll be checking in the below as obvious after some testing.  There are
some more calls to count_occurrences in auto-inc-dec.c which worry me a
bit, but that's a problem for another day.


Bernd

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