[llvm-dev] Prefixing DEBUG messages with DEBUG_TYPE (was re: [PATCH] D13259: LLE 6/6: Add LoopLoadElimination pass)

[Hal Finkel via llvm-dev]

----- Original Message -----
> From: "Matthias Braun via llvm-dev" <llvm-dev at lists.llvm.org>
> To: "Daniel Berlin" <dberlin at dberlin.org>
> Cc: "llvm-dev" <llvm-dev at lists.llvm.org>
> Sent: Monday, November 2, 2015 1:16:18 PM
> Subject: Re: [llvm-dev] Prefixing DEBUG messages with DEBUG_TYPE (was re: [PATCH] D13259: LLE 6/6: Add
> LoopLoadElimination pass)
> 
> To ask a basic question first: Why do we need prefixes at all? Are
> the messages that likely to be confused? As far as I understand this
> case it was only mentioned because of inconsistent prefix/no-prefix
> use, there was no indication that we should actually have them. So
> another possible solution would be to remove prefixes and avoiding
> the additional visual noise. Why add noise to every message just to
> improve upon the rare case of a messages origin being ambiguous?

I generally find the prefixes convenient when searching the debug output for debug messages from a particular pass.

 -Hal

> 
> - Matthias
> 
> > On Nov 2, 2015, at 11:04 AM, Daniel Berlin via llvm-dev
> > <llvm-dev at lists.llvm.org> wrote:
> > 
> > Moving this discussion here from the review thread.
> > 
> > RIght now, we have a few passes that prefix DEBUG message with
> > various things, so folks using -debug can tell where the debug
> > message came from.
> > 
> > But this is not consistent, and in fact, most passes don't do it.
> > 
> > Worse, the prefixes used do not often match the DEBUG_TYPE of the
> > pass.
> > 
> > It would be nice to fix this, and just have the DEBUG macros output
> > the debug type in front of messages if that's what folks want.
> > 
> > Of course, it turns out you can't just make the DEBUG macro do
> > something here, because people use it for more than just
> > outputting messages.
> > 
> > My thought was to just bite the bullet and make a DEBUG_MSG macro
> > that outputs the DEBUG_TYPE, and replace the appropriate existing
> > uses of DEBUG(dbgs() <<) with it.
> > 
> > Something like
> > #define DEBUG_MSG_WITH_TYPE(t, x) DEBUG_WITH_TYPE(t, dbgs() << t
> > <<":" << x;)
> > #define DEBUG_MSG(x) DEBUG_MSG_WITH_TYPE(DEBUG_TYPE, x)
> > 
> > Suggestions, however, welcome!
> > 
> > ---------- Forwarded message ----------
> > From: Renato Golin <renato.golin at linaro.org>
> > Date: Fri, Oct 30, 2015 at 10:15 AM
> > Subject: Re: [PATCH] D13259: LLE 6/6: Add LoopLoadElimination pass
> > To: anemet at apple.com, hfinkel at anl.gov, dberlin at dberlin.org
> > Cc: mssimpso at codeaurora.org, sanjoy at playingwithpointers.com,
> > llvm-commits at lists.llvm.org
> > 
> > 
> > rengolin added a comment.
> > 
> > In http://reviews.llvm.org/D13259#278362, @dberlin wrote:
> > 
> > > I would suggest rather than prefix *anything*, anywhere, that if
> > > we want
> > >  prefixes, we just have the DEBUG macro output the debug type in
> > >  front of
> > >  the message ;-)
> > 
> > 
> > Sounds good to me.
> > 
> > 
> > http://reviews.llvm.org/D13259
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> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory