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configure: fix NEON flag detection under gcc 6

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use a compile check on a separate file to avoid assuming using
arm_neon.h is safe to use without flags when just the file itself is
self-contained with GCC target pragmas.

BUG=webp:313

Change-Id: I48f92ae3e6e4a9468ea5b937c80a89ee40b2dcfd
This commit is contained in:
James Zern 2016-10-05 00:03:14 -07:00
parent 265abbe9b2
commit 0104d730bf
1 changed files with 46 additions and 34 deletions
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80
configure.ac
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@ -10,6 +10,7 @@ dnl === it must occur before LT_INIT (AC_PROG_LIBTOOL).
m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
AC_PROG_LIBTOOL
AC_PROG_SED
AM_PROG_CC_C_O
dnl === Enable less verbose output when building.
@ -195,40 +196,51 @@ AC_ARG_ENABLE([neon_rtcd],
AS_IF([test "x$enable_neon" != "xno"], [
case "$host_cpu" in
arm|armv7*)
dnl Test for NEON support with no flags.
AC_CHECK_HEADER([arm_neon.h],
[AC_DEFINE(WEBP_HAVE_NEON, [1],
[Set to 1 if NEON is supported])],
dnl Test for NEON support using -mfpu=neon
[unset ac_cv_header_arm_neon_h
NEON_FLAGS="$INTRINSICS_CFLAGS $NEON_FLAGS"
TEST_AND_ADD_CFLAGS([NEON_FLAGS], [-mfpu=neon])
AS_IF([test -n "$NEON_FLAGS"], [
SAVED_CFLAGS=$CFLAGS
CFLAGS="$CFLAGS $NEON_FLAGS"
AC_CHECK_HEADER([arm_neon.h],
[AS_IF([test "${host_os%%-*}" = "linux" -o \
"x$enable_neon_rtcd" = "xno"], [
AC_DEFINE(WEBP_HAVE_NEON, [1],
[Set to 1 if NEON is supported])],
[AC_MSG_WARN(m4_normalize([NEON runtime
cpu-detection is unavailble for
${host_os%%-*}. Force with
CFLAGS=-mfpu=neon or
--disable-neon-rtcd.]))
enable_neon_rtcd=no
NEON_FLAGS=""])],
[NEON_FLAGS=""])
CFLAGS=$SAVED_CFLAGS
AS_IF([test -n "$NEON_FLAGS"], [
dnl If NEON is available and rtcd is disabled apply
dnl NEON_FLAGS globally.
AS_IF([test "x$enable_neon_rtcd" = "xno"], [
AM_CFLAGS="$AM_CFLAGS $NEON_FLAGS"
NEON_FLAGS=""],
[AC_DEFINE(WEBP_HAVE_NEON_RTCD, [1],
[Set to 1 if runtime detection of NEON
is enabled])])])])])
# Test for NEON support without flags before falling back to -mfpu=neon
for flag in '' '-mfpu=neon'; do
LOCAL_NEON_FLAGS="$INTRINSICS_CFLAGS $NEON_FLAGS"
TEST_AND_ADD_CFLAGS([LOCAL_NEON_FLAGS], [$flag])
SAVED_CFLAGS=$CFLAGS
CFLAGS="$CFLAGS $LOCAL_NEON_FLAGS"
dnl Note AC_LANG_PROGRAM([]) uses an old-style main definition.
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <arm_neon.h>
int main(void) {
int8x8_t v = vdup_n_s8(0);
(void)v;
return 0;
}])],
[NEON_FLAGS="$(echo $LOCAL_NEON_FLAGS | $SED 's/^ *//')"
AS_IF([test -n "$NEON_FLAGS"], [
AS_IF([test "${host_os%%-*}" = "linux" -o \
"x$enable_neon_rtcd" = "xno"], [
CFLAGS=$SAVED_CFLAGS
AC_DEFINE(WEBP_HAVE_NEON, [1], [Set to 1 if NEON is supported])
break
],[
AC_MSG_WARN(m4_normalize([NEON runtime cpu-detection is
unavailable for ${host_os%%-*}. Force
with CFLAGS=-mfpu=neon or
--disable-neon-rtcd.]))
enable_neon_rtcd=no
NEON_FLAGS=""
])
],[
CFLAGS=$SAVED_CFLAGS
AC_DEFINE(WEBP_HAVE_NEON, [1], [Set to 1 if NEON is supported])
break
])])
CFLAGS=$SAVED_CFLAGS
done
AS_IF([test -n "$NEON_FLAGS"], [
# If NEON is available and rtcd is disabled apply NEON_FLAGS globally.
AS_IF([test "x$enable_neon_rtcd" = "xno"], [
AM_CFLAGS="$AM_CFLAGS $NEON_FLAGS"
NEON_FLAGS=""],
[AC_DEFINE(WEBP_HAVE_NEON_RTCD, [1],
[Set to 1 if runtime detection of NEON is enabled])])])
;;
esac
AC_SUBST([NEON_FLAGS])])