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Add configure infrastructure to detect support for C99's restrict.

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Will be used in later commits improving performance for a few key
routines where information about aliasing allows for significantly
better code generation.

This allows to use the C99 'restrict' keyword without breaking C89, or
for that matter C++, compilers. If not supported it's defined to be
empty.

Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
This commit is contained in:
Andres Freund
2017-10-11 16:01:52 -07:00
parent 5fa6b0d102
commit 0b974dba2d
4 changed files with 72 additions and 0 deletions
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46
configure vendored
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@ -11545,6 +11545,52 @@ _ACEOF
;;
esac
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
$as_echo_n "checking for C/C++ restrict keyword... " >&6; }
if ${ac_cv_c_restrict+:} false; then :
$as_echo_n "(cached) " >&6
else
ac_cv_c_restrict=no
# The order here caters to the fact that C++ does not require restrict.
for ac_kw in __restrict __restrict__ _Restrict restrict; do
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
typedef int * int_ptr;
int foo (int_ptr $ac_kw ip) {
return ip[0];
}
int
main ()
{
int s[1];
int * $ac_kw t = s;
t[0] = 0;
return foo(t)
;
return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
ac_cv_c_restrict=$ac_kw
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
test "$ac_cv_c_restrict" != no && break
done
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_restrict" >&5
$as_echo "$ac_cv_c_restrict" >&6; }
case $ac_cv_c_restrict in
restrict) ;;
no) $as_echo "#define restrict /**/" >>confdefs.h
;;
*) cat >>confdefs.h <<_ACEOF
#define restrict $ac_cv_c_restrict
_ACEOF
;;
esac
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for printf format archetype" >&5
$as_echo_n "checking for printf format archetype... " >&6; }
if ${pgac_cv_printf_archetype+:} false; then :