This is the mail archive of the
mailing list for the GCC project.
[vta] don't count cprop into debug insns as changes
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 20 Nov 2008 21:15:40 -0200
- Subject: [vta] don't count cprop into debug insns as changes
If we cprop during bypass *only* to debug insns, we'll end up deleting
trivially dead insns, rebuilding jump labels and cleaning up the cfg,
which, in the absence of debug insns, we wouldn't run at that point.
This leads to codegen differences detected by -fcompare-debug.
The information about changes in cprop isn't used for any other
purpose, so I arranged for debug insns to not be counted as changes,
in the patch that follows, which I'm about to install, completing
With this patch, i686, ppc64 and x86_64 (-linux-gnu) all bootstrap
(-O1, -O2 and -O3, all with -g -fcompare-debug) and build target
libraries (-O2 -g -fcompare-debug only). There are still a few
testsuite regressions I'm going to look into (without
-fcompare-debug), and still a bunch of -fcompare-debug reports during
a testsuite run that has it enabled. ia64 is still bootstrapping with
the very latest version of the patchset I've just installed. I
decided not to wait.
from Alexandre Oliva <email@example.com>
* gcse.c (cprop_insn): Don't count changes to debug insns as
--- gcc/gcse.c.orig 2008-10-10 09:31:05.000000000 -0300
+++ gcc/gcse.c 2008-11-20 01:25:36.000000000 -0200
@@ -3024,6 +3024,9 @@ cprop_insn (rtx insn, int alter_jumps)
+ if (changed && DEBUG_INSN_P (insn))
+ return 0;
Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/
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