checkasm: aarch64: Print the SVE vector length, if available

tests/checkasm/arm/checkasm_64.S

@@ -209,3 +209,13 @@ function checked_call, export=1
         ldp             x29, x30, [sp], #16
         ret
 endfunc
+
+#if HAVE_SVE
+ENABLE_SVE
+function sve_length, export=1
+        cntb            x0
+        lsl             x0,  x0,  #3
+        ret
+endfunc
+DISABLE_SVE
+#endif

tests/checkasm/checkasm.c

@@ -119,7 +119,9 @@ static const struct {
     { 0 }
 };
 
-#if ARCH_RISCV
+#if ARCH_AARCH64 && HAVE_SVE
+int checkasm_sve_length(void);
+#elif ARCH_RISCV
 int checkasm_get_vlenb(void);
 #endif
 
@@ -761,6 +763,11 @@ int main(int argc, char *argv[]) {
             snprintf(buf, sizeof(buf), "VLEN=%i bits, ", vlen);
         }
         fprintf(stderr, "checkasm: %susing random seed %u\n", buf, state.seed);
+#elif ARCH_AARCH64 && HAVE_SVE
+        char buf[48] = "";
+        if (cpu_flags & DAV1D_ARM_CPU_FLAG_SVE)
+            snprintf(buf, sizeof(buf), "SVE %d bits, ", checkasm_sve_length());
+        fprintf(stderr, "checkasm: %susing random seed %u\n", buf, state.seed);
 #else
         fprintf(stderr, "checkasm: using random seed %u\n", state.seed);
 #endif