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Re: remarks about g++ 4.3 and some comparison to msvc & icc on ia32
> On 1/28/07, tbp <tbptbp@gmail.com> wrote:
> >Let it be clear from the start this is a potshot and while those
> >trends aren't exactly new or specific to my code, i haven't tried to
> >provide anything but specific data from one of my app, on
> >win32/cygwin.
> >
> >Primo, gcc getting much better wrt inling exacerbates the fact that
> >it's not as good as other compilers at shrinking the stack frame size,
> >and perhaps as was suggested by Uros when discussing that point a pass
> >to address that would make sense.
> >As i'm too lazy to properly measure cruft across multiple compilers,
> >i'll use my rtrt app where i mostly control large scale inlining by
> >hand.
> >objdump -wdrfC --no-show-raw-insn $1|perl -pe 's/^\s+\w+:\s+//'|perl
> >-ne 'printf "%4d\n", hex($1) if /sub\s+\$(0x\w+),%esp/'|sort -r| head
> >-n 10
> >
> >msvc:2196 2100 1772 1692 1688 1444 1428 1312 1308 1160
> >icc: 2412 2280 2172 2044 1928 1848 1820 1588 1428 1396
> >gcc: 2604 2596 2412 2076 2028 1932 1900 1756 1720 1132
>
> It would have been nice to tell us what the particular columns in
> this table mean - now we have to decrypt objdump params and
> perl postprocessing ourselves.
>
> (If you are interested in stack size related to inlining you may want
> to tune --param large-stack-frame and --param large-stack-frame-growth).
Also having some testcases showing inlining deffects in GCC would be
very interesting for me. Now after IPA-SSA has been merged, I plan to
do some retuning of inliner for 4.3 release since a lot has changes
about properties of it's input and it was originally designed to operate
well on IL used by early tree-ssa.
Considering information about stack frame size in the inlining costs is
one of things I believe we should do but it is also dificult to tune
without interesting testcases for it.
Honza
>
> Richard.