dnl ===========================================================================
dnl Check for ARM SIMD instructions
-ARM_SIMD_CFLAGS="-mcpu=arm1136j-s"
+ARM_SIMD_CFLAGS=""
have_arm_simd=no
AC_MSG_CHECKING(whether to use ARM SIMD assembler)
-xserver_save_CFLAGS=$CFLAGS
-CFLAGS="$ARM_SIMD_CFLAGS $CFLAGS"
+# check with default CFLAGS in case the toolchain turns on a sufficiently recent -mcpu=
AC_COMPILE_IFELSE([
int main () {
asm("uqadd8 r1, r1, r2");
return 0;
-}], have_arm_simd=yes)
-CFLAGS=$xserver_save_CFLAGS
+}], have_arm_simd=yes,
+ # check again with an explicit -mcpu= in case the toolchain defaults to an
+ # older one; note that uqadd8 isn't available in Thumb mode on arm1136j-s
+ # so we force ARM mode
+ ARM_SIMD_CFLAGS="-mcpu=arm1136j-s -marm"
+ xserver_save_CFLAGS=$CFLAGS
+ CFLAGS="$ARM_SIMD_CFLAGS $CFLAGS"
+ AC_COMPILE_IFELSE([
+ int main () {
+ asm("uqadd8 r1, r1, r2");
+ return 0;
+ }], have_arm_simd=yes)
+ CFLAGS=$xserver_save_CFLAGS)
AC_ARG_ENABLE(arm-simd,
[AC_HELP_STRING([--disable-arm-simd],