Re: fix left-over debug insns in DCE

[Alexandre Oliva <aoliva at redhat dot com>]

On Jun  2, 2011, Eric Botcazou <ebotcazou@adacore.com> wrote:

> Why can't the problem be addressed purely within DF?

Hmm...  Maybe it could, I'm not sure.  The problem is that DCE removes
insns, and then DF associates remaining uses in debug insns to earlier
DEFs.  Adjusting debug insns in DCE is right per the VTA design motto:
decide as if debug insns weren't there, adjust them as you would adjust
non-debug insns.  This code borrowed from DF into DCE is the âadjustâ
bit.

> Starting to spill the DF 
> logic to individual RTL passes doesn't look very appealing to me.

Propagation of uses isn't DF-specific material, it just so happened that
it offered an adequate interface.  Other passes already have their own
propagation machinery, but it didn't look quite as suitable.

>> This is the patch I ended up with.  Regstrapped on x86_64-linux-gnu and
>> i686-linux-gnu.  Ok to install?

> OK for the usual debug insn bookkeeping, i.e.

Err...  These depend on the interface changes of functions defined
within DF to work.  Should they perhaps be moved out of DF-specific
files?

-- 
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