On 10/31/2016 12:08 PM, Paolo Bonzini wrote: > An unrolled loop avoids the cost of spawning sed in AS_TR_SH and > AS_TR_CPP. Prefer it if there is nothing in the second and third > argument of AC_CHECK_FUNCS and the first argument is a literal. > Modify AC_CHECK_FUNCS_ONCE to avoid the variable indirection too. > > * lib/autoconf/functions.m4 (AC_CHECK_FUNCS): Unroll loop if safe. > (_AC_CHECK_FUNCS): Move basic implementation here. > (_AC_CHECK_FUNC_ONCE): Expand AC_CHECK_FUNCS here... > (_AC_FUNCS_EXPANSION): ... and not here, so remove. > > Signed-off-by: Paolo Bonzini <[email protected]> > --- > lib/autoconf/functions.m4 | 25 +++++++++++-------------- > 1 file changed, 11 insertions(+), 14 deletions(-) > > diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4 > index 66abe29..ccfb053 100644 > --- a/lib/autoconf/functions.m4 > +++ b/lib/autoconf/functions.m4 > @@ -85,20 +85,24 @@ m4_define([_AH_CHECK_FUNC], > # `break' to stop the search. > AC_DEFUN([AC_CHECK_FUNCS], > [m4_map_args_w([$1], [_AH_CHECK_FUNC(], [)])]dnl > -[AS_FOR([AC_func], [ac_func], [$1], > -[AC_CHECK_FUNC(AC_func, > - [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]AC_func)) $2], > - [$3])dnl]) > +[m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes], > + [m4_map_args_w([$1], [_$0(], [)])], > + [AS_FOR([AC_func], [ac_func], [$1], [_$0(AC_func, [$2], [$3])])])
Dropping the dnl adds a lot of blank lines to configure scripts, I will
massage that slightly.
> ])# AC_CHECK_FUNCS
>
> +m4_define([_AC_CHECK_FUNCS],
> +[AC_CHECK_FUNC([$1],
> + [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]$1)) $2],
> + [$3])
> +])
> +
I tested this with coreutils. Timing wise, on my system, I was able to
consistently see a reduction of './config.status --recheck' execution
time from around 34.3s pre-patch, to around 33.9s post-patch; a little
better than 1%. That's not huge, but big enough that I can say it is a
real improvement and not just measurement noise.
Size-wise, this results in about 17k of growth in the size of coreutils'
configure script. There is no longer an ac_func_list (which shaved some
lines up front), but unrolling the loop means you now have a lot of code
additions that look like:
+ac_fn_c_check_func "$LINENO" "btowc" "ac_cv_func_btowc"
+if test "x$ac_cv_func_btowc" = xyes
+then :
+ cat >>confdefs.h <<_ACEOF
+#define HAVE_BTOWC 1
+_ACEOF
+
+fi
+
(there's that blank line I mentioned earlier)
It makes me wonder if we want a followup patch with some sort of new:
# ac_fn_c_check_func_simple line func cache witness
ac_fn_c_check_func_simple () {
ac_fn_c_check_func "$1" "$2" "$3"
if eval test "x\$$3" = xyes; then
printf "#define $4\n" >>confdefs.h
fi
}
so that we can compress call current 9-line call sites to a 1-line:
ac_fn_c_check_func_simple "$LINENO" "btowc" "ac_cv_func_btowc" "HAVE_BTWOC"
or maybe it will be easier to maintain via a 2-line approach:
ac_fn_c_check_func "$LINENO" "btowc" "ac_cv_func_btowc"
ac_fn_simple_define "ac_cv_func_btowc" "HAVE_BTOWC"
At any rate, that's food for a later patch (which I'm playing with), so
it shouldn't stop me from committing your patch.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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