Re: [RFC] Optimization Diary

[Devang Patel <devang dot patel at gmail dot com>]

Andrew Pinski wrote:
> > Andrew Pinski wrote:
> >     
> > > > These are not warnings and they should not cause build failures
> > > > when -Werror is used, hence warnings are not suitable medium to
> > > > communicate this info.
> > > >     
> > > >         
> > > There is a third type of diagnostic in GCC which gets not much
> > > use at all.  It is called note.  It might be interesting to use that instead
> > > of saying there is no way to cause no build failures with warnings.
> > >   
> > >       
> > That's what I meant when I said "hints" ...
> >
> > "However, GCC provides (notes) along with warnings and errors. But they
> > all reside in build log. While doing performance analysis, build log
> > may not be available hence it is required to have it on disk somewhere. "
> >     
>
> If you are doing performance analysis the build log better be able to look
> at to make sure you are building with the correct options unless you trust
> the IDEs (which I and many other people don't).
>   
Two things.

First this is not about IDE vs no IDE. Lets take one example.
We, here at Apple, do not use IDE to build GCC. However we routinely
install pre built compiler package on various machines and do compile
time performance analysis using Shark. When Shark points me to a code
hot spot, I want to know what optimizer was thinking about it.

Second, optimization diary is not about what options are enabled and
disabled. Compiler should not invoke any particular optimization pass
just to add optimization diary entry. Its is a diary of optimization passes
that are active.

-
Devang

[ Interestingly, there is a long standing request, here at Apple, to list
 command line options in object file (even when optimization is not used).
 One of our intern tried to put them in STABS string. It may be a good
 idea to use DWARF in that case also. However it is orthogonal to
 optimization diary. It is a good small project, if someone is 
interested. ]