First pass at ARMv8 64-bit NEON SIMD support

acinclude.m4

@@ -210,3 +210,36 @@ AC_DEFUN([AC_CHECK_COMPATIBLE_MIPSEL_ASSEMBLER_IFELSE],[
     $2
   fi
 ])
+
+AC_DEFUN([AC_CHECK_COMPATIBLE_ARM64_ASSEMBLER_IFELSE],[
+  ac_good_gnu_arm_assembler=no
+  ac_save_CC="$CC"
+  ac_save_CFLAGS="$CFLAGS"
+  CFLAGS="$CCASFLAGS -x assembler-with-cpp"
+  CC="$CCAS"
+  AC_COMPILE_IFELSE([[
+    .text
+    movi v0.16b, #100]], ac_good_gnu_arm_assembler=yes)
+
+  ac_use_gas_preprocessor=no
+  if test "x$ac_good_gnu_arm_assembler" = "xno" ; then
+    CC="gas-preprocessor.pl $CCAS"
+    AC_COMPILE_IFELSE([[
+      .text
+      movi v0.16b, #100]], ac_use_gas_preprocessor=yes)
+  fi
+  CFLAGS="$ac_save_CFLAGS"
+  CC="$ac_save_CC"
+
+  if test "x$ac_use_gas_preprocessor" = "xyes" ; then
+    CCAS="gas-preprocessor.pl $CCAS"
+    AC_SUBST([CCAS])
+    ac_good_gnu_arm_assembler=yes
+  fi
+
+  if test "x$ac_good_gnu_arm_assembler" = "xyes" ; then
+    $1
+  else
+    $2
+  fi
+])

configure.ac

@@ -430,7 +430,23 @@ if test "x${with_simd}" != "xno"; then
           AC_MSG_ERROR([SIMD support can't be enabled.])
         else
           AC_MSG_WARN([SIMD support can't be enabled.  Performance will suffer.])
+        fi
       fi
+      ;;
+    aarch64*)
+      AC_MSG_RESULT([yes (arm64)])
+      AC_MSG_CHECKING([if the assembler is GNU-compatible and can be used])
+      AC_CHECK_COMPATIBLE_ARM64_ASSEMBLER_IFELSE(
+        [AC_MSG_RESULT([yes])
+         simd_arch=aarch64],
+        [AC_MSG_RESULT([no])
+         with_simd=no])
+      if test "x${with_simd}" = "xno"; then
+        if test "x${require_simd}" = "xyes"; then
+          AC_MSG_ERROR([SIMD support can't be enabled.])
+        else
+          AC_MSG_WARN([SIMD support can't be enabled.  Performance will suffer.])
+        fi
       fi
       ;;
     mipsel*)
@@ -472,6 +488,7 @@ AM_CONDITIONAL([WITH_SSE_FLOAT_DCT], [test "x$simd_arch" = "xx86_64" -o "x$simd_
 AM_CONDITIONAL([SIMD_I386], [test "x$simd_arch" = "xi386"])
 AM_CONDITIONAL([SIMD_X86_64], [test "x$simd_arch" = "xx86_64"])
 AM_CONDITIONAL([SIMD_ARM], [test "x$simd_arch" = "xarm"])
+AM_CONDITIONAL([SIMD_ARM_64], [test "x$simd_arch" = "xaarch64"])
 AM_CONDITIONAL([SIMD_MIPSEL], [test "x$simd_arch" = "xmipsel"])
 AM_CONDITIONAL([X86_64], [test "x$host_cpu" = "xx86_64" -o "x$host_cpu" = "xamd64"])
 AM_CONDITIONAL([WITH_TURBOJPEG], [test "x$with_turbojpeg" != "xno"])

simd/Makefile.am

@@ -58,6 +58,12 @@ libsimd_la_SOURCES = jsimd_arm.c jsimd_arm_neon.S
 
 endif
 
+if SIMD_ARM_64
+
+libsimd_la_SOURCES = jsimd_arm.c jsimd_arm_neon_64.S
+
+endif
+
 if SIMD_MIPSEL
 
 libsimd_la_SOURCES = jsimd_mips.c jsimd_mips_dspr2_asm.h jsimd_mips_dspr2.S