[PATCH][RTL-ifcvt] Reject insns that are multiple_sets

[Kyrill Tkachov]

Hi all,

As discussed, I've added a check for multiple_sets to insn_valid_noce_process_p 
and replaced the
modified_a and modified_b redundant definitions with
checking asserts to catch cases if any unexpected multiple
sets get through the net.

Bootstrapped and tested on arm, aarch64, x86_64.
As expected, I didn't see any codegen difference as it should a pretty rare
case for which we have no reported testcase.

Ok for trunk?

Thanks,
Kyrill

2015-11-27  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    * ifcvt.c (insn_valid_noce_process_p): Reject insn if it satisfies
    multiple_sets.
    (noce_try_cmove_arith): Add checking asserts that orig_a and orig_b
    are not modified by the final modified insns in the basic blocks

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 3ce9fe6082069361504268788c009eec722ac89b..ef3ebe359a3ef80965f9827c67a7cb6b0dca1442 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -1880,6 +1880,7 @@ insn_valid_noce_process_p (rtx_insn *insn, rtx cc)
 {
   if (!insn
       || !NONJUMP_INSN_P (insn)
+      || multiple_sets (insn)
       || (cc && set_of (cc, insn)))
       return false;
 
@@ -2206,7 +2207,7 @@ noce_try_cmove_arith (struct noce_if_info *if_info)
        swap insn that sets up A with the one that sets up B.  If even
        that doesn't help, punt.  */
 
-  modified_in_a = emit_a != NULL_RTX && modified_in_p (orig_b, emit_a);
+  gcc_checking_assert (!emit_a || !modified_in_p (orig_b, emit_a));
   if (tmp_b && then_bb)
     {
       FOR_BB_INSNS (then_bb, tmp_insn)
@@ -2222,7 +2223,7 @@ noce_try_cmove_arith (struct noce_if_info *if_info)
     }
   if (emit_a || modified_in_a)
     {
-      modified_in_b = emit_b != NULL_RTX && modified_in_p (orig_a, emit_b);
+      gcc_checking_assert (!emit_b || !modified_in_p (orig_a, emit_b));
       if (tmp_b && else_bb)
 	{
 	  FOR_BB_INSNS (else_bb, tmp_insn)