simple way to test some __ARM_<> values

neon/ifDefNeon.c

@@ -0,0 +1,78 @@
+/* neon_example.c - Neon intrinsics example program */
+#include <stdint.h>
+#include <stdio.h>
+#include <assert.h>
+#include <arm_neon.h>
+/* fill array with increasing integers beginning with 0 */
+void fill_array(int16_t *array, int size)
+{    int i;
+    for (i = 0; i < size; i++)
+    {
+         array[i] = i;
+    }
+}
+/* return the sum of all elements in an array. This works by calculating 4 totals (one for each lane) and adding those at the end to get the final total */
+int sum_array(int16_t *array, int size)
+{
+     /* initialize the accumulator vector to zero */
+     int16x4_t acc = vdup_n_s16(0);
+     int32x2_t acc1;
+     int64x1_t acc2;
+     /* this implementation assumes the size of the array is a multiple of 4 */
+     assert((size % 4) == 0);
+     /* counting backwards gives better code */
+     for (; size != 0; size -= 4)
+     {
+          int16x4_t vec;
+          /* load 4 values in parallel from the array */
+          vec = vld1_s16(array);
+          /* increment the array pointer to the next element */
+          array += 4;
+          /* add the vector to the accumulator vector */
+          acc = vadd_s16(acc, vec);
+      }
+      /* calculate the total */
+      acc1 = vpaddl_s16(acc);
+      acc2 = vpaddl_s32(acc1);
+      /* return the total as an integer */
+      return (int)vget_lane_s64(acc2, 0);
+}
+/* main function */
+int main()
+{
+/*      int16_t my_array[100];
+      fill_array(my_array, 100);
+      printf("Sum was %d\n", sum_array(my_array, 100));
+      return 0;
+*/
+#ifdef __ARM_NEON
+	printf("__ARM_NEON true \n");
+#else
+	printf("__ARM_NEON false \n");
+#endif
+
+#ifdef __ARM_NEON_FP
+        printf("__ARM_NEON_FP true \n");
+#else
+        printf("__ARM_NEON_FP false \n");
+#endif
+
+#ifdef __ARM_FEATURE_FMA
+        printf("__ARM_FEATURE_FMA true, but FMA enabled only if __ARM_NEON_FP also true \n");
+#else
+        printf("__ARM_FEATURE_FMA false \n");
+#endif
+
+#ifdef __ARM_TEST_IFDEF
+        printf("__ARM_TEST_IFDEF true \n");
+#else
+        printf("__ARM_TEST_IFDEF false \n");
+#endif
+
+#ifdef __ARM_ARCH
+        printf("__ARM_ARCH true with value %d \n", __ARM_ARCH );
+#else
+        printf("__ARM_ARCH false \n");
+#endif
+}
+