[src/netbsd-1-4]: src/gnu/dist/gcc pull up revs 1.2-1.3 from trunk via patch ...

[cgd <cgd%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/901c18cc654d
branches:  netbsd-1-4
changeset: 469680:901c18cc654d
user:      cgd <cgd%NetBSD.org@localhost>
date:      Mon Nov 08 06:58:45 1999 +0000

description:
pull up revs 1.2-1.3 from trunk via patch (requested by drochner):
  Fix a misoptimization by disabling the optimization in certain cases.

diffstat:

 gnu/dist/gcc/combine.c |  49 +------------------------------------------------
 1 files changed, 1 insertions(+), 48 deletions(-)

diffs (62 lines):

diff -r 99a1c4e9fc58 -r 901c18cc654d gnu/dist/gcc/combine.c
--- a/gnu/dist/gcc/combine.c    Mon Nov 08 06:41:31 1999 +0000
+++ b/gnu/dist/gcc/combine.c    Mon Nov 08 06:58:45 1999 +0000
@@ -10752,57 +10752,10 @@
     return 0;
 
   /* If the value was set in a later insn than the ones we are processing,
-     we can't use it even if the register was only set once, but make a quick
-     check to see if the previous insn set it to something.  This is commonly
-     the case when the same pseudo is used by repeated insns.
-
-     This does not work if there exists an instruction which is temporarily
-     not on the insn chain.  */
-
+     we can't use it even if the register was only set once.  */
   if (INSN_CUID (reg_last_set[regno]) >= subst_low_cuid)
-    {
-      rtx insn, set;
-
-      /* We can not do anything useful in this case, because there is
-        an instruction which is not on the insn chain.  */
-      if (subst_prev_insn)
        return 0;
 
-      /* Skip over USE insns.  They are not useful here, and they may have
-        been made by combine, in which case they do not have a INSN_CUID
-        value.  We can't use prev_real_insn, because that would incorrectly
-        take us backwards across labels.  Skip over BARRIERs also, since
-        they could have been made by combine.  If we see one, we must be
-        optimizing dead code, so it doesn't matter what we do.  */
-      for (insn = prev_nonnote_insn (subst_insn);
-          insn && ((GET_CODE (insn) == INSN
-                    && GET_CODE (PATTERN (insn)) == USE)
-                   || GET_CODE (insn) == BARRIER
-                   || INSN_CUID (insn) >= subst_low_cuid);
-          insn = prev_nonnote_insn (insn))
-       ;
-
-      if (insn
-         && (set = single_set (insn)) != 0
-         && rtx_equal_p (SET_DEST (set), x))
-       {
-         value = SET_SRC (set);
-
-         /* Make sure that VALUE doesn't reference X.  Replace any
-            explicit references with a CLOBBER.  If there are any remaining
-            references (rare), don't use the value.  */
-
-         if (reg_mentioned_p (x, value))
-           value = replace_rtx (copy_rtx (value), x,
-                                gen_rtx_CLOBBER (GET_MODE (x), const0_rtx));
-
-         if (reg_overlap_mentioned_p (x, value))
-           return 0;
-       }
-      else
-       return 0;
-    }
-
   /* If the value has all its registers valid, return it.  */
   if (get_last_value_validate (&value, reg_last_set[regno],
                               reg_last_set_label[regno], 0))