https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=677681 can be
“fixed” by disabling the artificial dependency of a debug insn on its
previous insn.
Debug insns will often depend on their prevs anyway, in a use/def
relationship, but if the def was (re)moved or the use was reset, this
artificial dep helped keep the debug insn “in place”.
Being a very imperfect heuristic, it's not clear that it helps more than
it harms. Thoughts? Regstrapped on x86_64-linux-gnu and
i686-linux-gnu.
for gcc/ChangeLog
from Alexandre Oliva <aol...@redhat.com>
* sched-deps.c (sched_analyze_insn): Don't force debug insns
to follow their original predecessors.
Index: gcc/sched-deps.c
===================================================================
--- gcc/sched-deps.c.orig 2011-02-24 09:54:12.016654388 -0300
+++ gcc/sched-deps.c 2011-02-24 09:55:48.456918435 -0300
@@ -2816,7 +2816,7 @@ sched_analyze_insn (struct deps_desc *de
additional analysis can modify the generated code. */
prev = PREV_INSN (insn);
-
- if (prev && NONDEBUG_INSN_P (prev))
- add_dependence (insn, prev, REG_DEP_ANTI);
}
else
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer
