[vta] don't look for overlapping uses in debug insns

[Alexandre Oliva]

combine took a different turn on i686 bootstrap-debug when it found a
use of a pseudo in a debug insn, and it ended up not performing a
combination that, without the debug insn, it would perform.  This
mustn't happen.

propagate_for_debug (introduced in the branch a while ago) will take
care of adjusting any uses in debug insns that need adjusting because
of the combination, but it looks like it might cause silent breakage
of debug information in postreload-gcse.  I'll have to look into that
but, for now, I'm going ahead and checking this in.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: vta-rtlanal-reg-used-between.patch
Type: text/x-patch
Size: 682 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/gcc-patches/attachments/20080103/68255ff2/attachment.bin>
-------------- next part --------------

-- 
Alexandre Oliva         http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member         http://www.fsfla.org/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}