[Bug c/112422] New: Build process does a redundant number of checks ?

[Bug c/112422] New: Build process does a redundant number of checks ?

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112422

            Bug ID: 112422
           Summary: Build process does a redundant number of checks ?
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

I just ran a gcc trunk build. The configure line was

CC="clang" CXX="clang++" \
../trunk.year/configure --prefix=/home/dcb38/gcc/results.$DATE.asan.ubsan \
    --disable-multilib \
    --disable-bootstrap \
    --with-build-config=bootstrap-asan \
    --with-build-config=bootstrap-ubsan \
    --with-pkgversion=$HASH \
    --enable-checking=df,extra,fold,rtl,yes \
    --enable-languages=c,c++,fortran

The command I used was 

$ (date;make -j 20;date) > mk.out 2>&1
$ grep "checking for" mk.out | sort -k 2 | uniq -c | sort -rn > 1.out
$ head 1.out
     20 checking for C compiler default output file name... a.out
     19 checking for a BSD-compatible install... /usr/bin/install -c
     18 checking for egrep... /usr/bin/grep -E
     17 checking for x86_64-pc-linux-gnu-ranlib... ranlib 
     17 checking for x86_64-pc-linux-gnu-ar... ar 
     17 checking for unistd.h... (cached) yes
     15 checking for x86_64-pc-linux-gnu-objdump... objdump
     15 checking for minix/config.h... no
     14 checking for gawk... gawk
     12 checking for x86_64-pc-linux-gnu-gcc... clang

That seems a lot of redundant checking to me. 

Perhaps the build process could be made faster by only checking some properties 
once and remembering the result for later ?

[Bug bootstrap/112422] Build process does a redundant number of checks ?

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112422

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |bootstrap

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I doubt configure is where most of the time is spent these days.

[Bug bootstrap/112422] Build process does a redundant number of checks ?

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112422

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.org
           Keywords|                            |build

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
A lot of that's just the way that autoconf works. You'd probably have to change
the upstream implementation of certain autoconf macros to fix this.
Alternatively, you could also try configuring with the "-C" flag to your
configure script, which should cause configure results to be cached, but that
can be rather fragile, as the config.cache files can stop your build if the
slightest things to change. I suppose GCC could try sharing its config.cache
files more widely between its various subdirectories, but that would be
somewhat risky, given that some of the things that configure checks for could
change due to the whole bootstrap process (fixincludes changes the headers
available, the new compiler getting built changes which compiler should be
found, and what features it has, the new runtime libraries getting built change
what functions are available, and so on...)

[Bug bootstrap/112422] Build process does a redundant number of checks ?

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112422

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |84402
                 CC|                            |sjames at gcc dot gnu.org

--- Comment #3 from Sam James <sjames at gcc dot gnu.org> ---
There's some stuff we could cache for sure but it wouldn't be the majority of
the checks - stuff like finding tools like awk, sed should work regardless of
which stage we're in and so on.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84402
[Bug 84402] [meta] GCC build system: parallelism bottleneck

[Bug bootstrap/112422] Build process does a redundant number of checks ?

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112422

--- Comment #4 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Sam James from comment #3)
> There's some stuff we could cache for sure but it wouldn't be the majority
> of the checks - stuff like finding tools like awk, sed should work
> regardless of which stage we're in and so on.

gawk and sed were potential host modules at one point previously, too, but it
looks like they've been removed, so yeah I guess it'd be safe for them now...
anything that might fall in this category should get checked against
Makefile.def to make sure there aren't already potential modules for them for
people trying to combine trees or something...