configure: Check for support for AArch64 SVE and SVE2

We don't expect the user to build the whole x264 codebase with
SVE/SVE2 enabled, as we only enable this feature for the assembly
files that use it, in order to have binaries that are portable
and enable the SVE codepaths at runtime if supported.

configure

@@ -411,7 +411,8 @@ NL="
 # list of all preprocessor HAVE values we can define
 CONFIG_HAVE="MALLOC_H ALTIVEC ALTIVEC_H MMX ARMV6 ARMV6T2 NEON AARCH64 BEOSTHREAD POSIXTHREAD WIN32THREAD THREAD LOG2F SWSCALE \
              LAVF FFMS GPAC AVS GPL VECTOREXT INTERLACED CPU_COUNT OPENCL THP LSMASH X86_INLINE_ASM AS_FUNC INTEL_DISPATCHER \
-             MSA LSX MMAP WINRT VSX ARM_INLINE_ASM STRTOK_R CLOCK_GETTIME BITDEPTH8 BITDEPTH10"
+             MSA LSX MMAP WINRT VSX ARM_INLINE_ASM STRTOK_R CLOCK_GETTIME BITDEPTH8 BITDEPTH10 \
+             SVE SVE2"
 
 # parse options
 
@@ -1003,6 +1004,8 @@ if [ $asm = auto -a $ARCH = AARCH64 ] ; then
     elif cc_check '' '' '__asm__("cmeq v0.8h, v0.8h, #0");' ; then
         define HAVE_AARCH64
         define HAVE_NEON
+        cc_check '' '' '__asm__(".arch armv8.2-a+sve  \n ptrue p0.b, vl16");'         && define HAVE_SVE
+        cc_check '' '' '__asm__(".arch armv8.2-a+sve2 \n smlalb z10.s, z2.h, z1.h");' && define HAVE_SVE2
         ASFLAGS="$ASFLAGS -c"
     else
         echo "no NEON support, try adding -mfpu=neon to CFLAGS"