[PATCH] Fix PR91522

[Richard Biener]

This fixes quadraticness in STV and makes

 machine dep reorg                  :  89.07 ( 95%)   0.02 ( 18%)  89.10 ( 
95%)      54 kB (  0%)

drop to zero.  Anybody remembers why it is the way it is now?

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

OK?

Thanks,
Richard.

2019-08-22  Richard Biener  <rguent...@suse.de>

        PR target/91522
        * config/i386/i386-features.c (scalar_chain::add_insn): Do not
        iterate over all defs of a reg.

Index: gcc/config/i386/i386-features.c
===================================================================
--- gcc/config/i386/i386-features.c     (revision 274764)
+++ gcc/config/i386/i386-features.c     (working copy)
@@ -419,10 +419,7 @@ scalar_chain::add_insn (bitmap candidate
   df_ref def;
   for (ref = DF_INSN_UID_DEFS (insn_uid); ref; ref = DF_REF_NEXT_LOC (ref))
     if (!HARD_REGISTER_P (DF_REF_REG (ref)))
-      for (def = DF_REG_DEF_CHAIN (DF_REF_REGNO (ref));
-          def;
-          def = DF_REF_NEXT_REG (def))
-       analyze_register_chain (candidates, def);
+      analyze_register_chain (candidates, ref);
   for (ref = DF_INSN_UID_USES (insn_uid); ref; ref = DF_REF_NEXT_LOC (ref))
     if (!DF_REF_REG_MEM_P (ref))
       analyze_register_chain (candidates, ref);