Re: issues with inlining

[Michel LESPINASSE <walken at zoy dot org>]

Hi Carlo,

On Thu, Dec 19, 2002 at 02:22:12AM +0100, Carlo Wood wrote:
> The following problems have been spotted:

[quoted below]

Did you get any replies to your email ? I've complained about just the
same issues previously without much success... issues 1) and 2) being
the most important for me.

Cheers,

> 1) -Winline doesn't give me a warning when a function is
>    not inlined, even while I am using the inline keyword
>    for it.
> 2) g++ 3.2.1 seems to totally ignore the inline keyword
>    and do as it pleases when being used with -O3.  
>    Unfortunately, I know better than the compiler what
>    should be inlined - so, ignoring the inline keyword
>    and inlining other functions results in much slower
>    code.
> 3) Apparently gcc is still inlining "top down", meaning
>    that when a() calls b() which calls c() which calls d(),
>    then b() is inlined into a(), c() is inlined into
>    d() and when then the function becomes too big, it
>    stops.  THIS IS HORRIBLE!!!  This *definitely* needs
>    to be changed into that d() is inlined into c(),
>    and if the function isn't getting too big, then c()
>    into b() etc.
> 4) The instruction limit that can be set with -finline-limit
>    seems to count instructions before optimization...
>    This means that I need to give a limit of 8000 instructions
>    before everything is inlined - although after optimization
>    hardly anything is left (maybe 50 to 100 instructions, way
>    below the default 600 threshold).
>    By the time I get my inner functions inlined this way,
>    EVERYTHING is inlined (I get one big function call of
>    120,000 instructions :/ (after compiling 60 minutes)).

-- 
Michel "Walken" LESPINASSE
Is this the best that god can do ? Then I'm not impressed.