config: add SVE detection alongside NEON in aarch64 op component

- Introduce AC_CACHE_CHECK probes for ARM Scalable Vector Extension (SVE)
  using both a default compile test and a second test with __attribute__((__target__("+sve"))).
- Define variables op_cv_sve_support and op_cv_sve_add_flags
- Update AM_CONDITIONAL and AC_DEFINE to expose SVE support macros
  (OMPI_MCA_OP_HAVE_SVE, OMPI_MCA_OP_SVE_EXTRA_FLAGS).
- Extend final AS_IF to enable the component when either NEON or SVE is available.

Signed-off-by: Marco Vogel <marco.vogel@fernuni-hagen.de>

Author: vogma

ompi/mca/op/aarch64/configure.m4

@@ -17,6 +17,7 @@
 # ------------------------------------------------
 AC_DEFUN([MCA_ompi_op_aarch64_CONFIG],[
     AC_CONFIG_FILES([ompi/mca/op/aarch64/Makefile])
+
     case "${host}" in
         aarch64*|arm64*)
             op_aarch64_check="yes";;
@@ -71,49 +72,95 @@ AC_DEFUN([MCA_ompi_op_aarch64_CONFIG],[
                             [op_cv_neon_fp_support=yes],
                             [op_cv_neon_fp_support=no])])])
 
-           #
+    
+                  #
            # Check for SVE support
            #
-           AC_CACHE_CHECK([for SVE support], op_cv_sve_support,
-                 [AS_IF([test "$op_cv_neon_support" = "yes"],
-                        [
-                          AC_LINK_IFELSE(
-                              [AC_LANG_PROGRAM([[
+           AC_CACHE_CHECK([for SVE support], [op_cv_sve_support], [
+             AC_MSG_RESULT([])      
+             # initialize result variables
+             op_cv_sve_support=no
+             op_cv_sve_add_flags=no
+
+             # first attempt: no extra flags
+             AC_MSG_CHECKING([for SVE support (no additional flags)])
+             AC_LINK_IFELSE(
+               [AC_LANG_SOURCE([[
 #if defined(__aarch64__) && defined(__ARM_FEATURE_SVE)
-#include <arm_sve.h>
+  #include <arm_sve.h>
 #else
-#error "No support for __aarch64__ or SVE"
+  #error "No support for __aarch64__ or SVE"
 #endif
-                                             ]],
-                                             [[
-#if defined(__aarch64__) && defined(_ARM_FEATURE_SVE)
-    svfloat32_t vA;
-    vA = svdup_n_f32(0)
+
+int main(void) {
+  svfloat32_t vA;
+  vA = svdup_n_f32(0);
+  return 0;
+}
+               ]])],
+               [ op_cv_sve_support=yes
+                 AC_MSG_RESULT([yes]) ],
+               [ AC_MSG_RESULT([no ]) ]
+             )
+
+             # second attempt: use +sve attribute
+             AS_IF([test "$op_cv_sve_support" = "no"],[
+               AC_MSG_CHECKING([for SVE support (with +sve)])
+               AC_LINK_IFELSE(
+                 [AC_LANG_SOURCE([[
+#if defined(__aarch64__)
+  #include <arm_sve.h>
+#else
+  #error "not on aarch64"
 #endif
-                                             ]])],
-                      [op_cv_sve_support=yes],
-                      [op_cv_sve_support=no])])])
-          ])
 
+__attribute__((__target__("+sve")))
+int main(void) {
+  svbool_t    pg = svptrue_b32();
+  svuint32_t  a  = svdup_u32(0);
+  svuint32_t  b  = svdup_u32(0);
+  svuint32_t  c  = svadd_u32_m(pg, a, b);
+  return (int)svaddv_u32(pg, c);
+}
+                 ]])],
+                 [ op_cv_sve_support=yes
+                   op_cv_sve_add_flags=yes
+                   AC_MSG_RESULT([yes]) ],
+                 [ AC_MSG_RESULT([no ]) ]
+               )
+             ])
+           ])
+
+           # restore the language after our C tests
+           AC_LANG_POP
+])
     AM_CONDITIONAL([MCA_BUILD_ompi_op_has_neon_support],
                    [test "$op_cv_neon_support" = "yes"])
     AM_CONDITIONAL([MCA_BUILD_ompi_op_has_neon_fp_support],
                    [test "$op_cv_neon_fp_support" = "yes"])
     AM_CONDITIONAL([MCA_BUILD_ompi_op_has_sve_support],
                    [test "$op_cv_sve_support" = "yes"])
+    AM_CONDITIONAL([MCA_BUILD_ompi_op_sve_add_flags],
+                   [test "$op_cv_sve_add_flags" = "yes"])
+
     AC_SUBST(MCA_BUILD_ompi_op_has_neon_support)
     AC_SUBST(MCA_BUILD_ompi_op_has_neon_fp_support)
     AC_SUBST(MCA_BUILD_ompi_op_has_sve_support)
+    AC_SUBST(MCA_BUILD_ompi_op_sve_add_flags)
 
     AS_IF([test "$op_cv_neon_support" = "yes"],
           [AC_DEFINE([OMPI_MCA_OP_HAVE_NEON], [1],[NEON supported in the current build])])
     AS_IF([test "$op_cv_neon_fp_support" = "yes"],
           [AC_DEFINE([OMPI_MCA_OP_HAVE_NEON_FP], [1],[NEON FP supported in the current build])])
     AS_IF([test "$op_cv_sve_support" = "yes"],
           [AC_DEFINE([OMPI_MCA_OP_HAVE_SVE], [1],[SVE supported in the current build])])
+    AS_IF([test "$op_cv_sve_add_flags" = "yes"],
+          [AC_DEFINE([OMPI_MCA_OP_SVE_EXTRA_FLAGS], [1],[SVE supported with additional compile attributes])])
 
-    # If we have at least support for Neon
-    AS_IF([test "$op_cv_neon_support" = "yes"],
+
+    # If we have at least support for Neon or SVE
+    AS_IF([test "$op_cv_neon_support" = "yes" || test "$op_cv_sve_support" = "yes" ],
           [$1],
           [$2])
+
 ])dnl