Fix aarch64 sbgemv_t compilation error for GCC < 13

Author: annop-w

CONTRIBUTORS.md

@@ -237,6 +237,7 @@ In chronological order:
   * [2025-01-10] Add thread throttling profile for SGEMM on NEOVERSEV1
   * [2025-01-21] Optimize gemv_t_sve_v1x3 kernel
   * [2025-02-26] Add sbgemv_t_bfdot kernel
+  * [2025-03-12] Fix aarch64 sbgemv_t compilation error for GCC < 13
 
 * Marek Michalowski <marek.michalowski@arm.com>
   * [2025-01-21] Add thread throttling profile for SGEMV on `NEOVERSEV1`

kernel/arm64/sbgemv_t_bfdot.c

@@ -33,11 +33,6 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <arm_neon.h>
 #include "common.h"
 
-static inline float bf16_to_fp32(bfloat16 bf16) {
-  uint32_t fp32 = (uint32_t)bf16 << 16;
-  return *((float*)&fp32);
-}
-
 int CNAME(BLASLONG m, BLASLONG n, float alpha, bfloat16 *a, BLASLONG lda, bfloat16 *x, BLASLONG incx, float beta, float *y, BLASLONG incy)
 {
   if (m < 1 || n < 1) return(0);
@@ -132,10 +127,10 @@ int CNAME(BLASLONG m, BLASLONG n, float alpha, bfloat16 *a, BLASLONG lda, bfloat
       }
 
       for (; i < m; ++i) {
-        y0_ptr[iy] += alpha * a0_ptr[i] * x_ptr[i];
-        y1_ptr[iy] += alpha * a1_ptr[i] * x_ptr[i];
-        y2_ptr[iy] += alpha * a2_ptr[i] * x_ptr[i];
-        y3_ptr[iy] += alpha * a3_ptr[i] * x_ptr[i];
+        y0_ptr[iy] += alpha * vcvtah_f32_bf16(a0_ptr[i]) * vcvtah_f32_bf16(x_ptr[i]);
+        y1_ptr[iy] += alpha * vcvtah_f32_bf16(a1_ptr[i]) * vcvtah_f32_bf16(x_ptr[i]);
+        y2_ptr[iy] += alpha * vcvtah_f32_bf16(a2_ptr[i]) * vcvtah_f32_bf16(x_ptr[i]);
+        y3_ptr[iy] += alpha * vcvtah_f32_bf16(a3_ptr[i]) * vcvtah_f32_bf16(x_ptr[i]);
       }
 
       iy += incy;
@@ -177,7 +172,7 @@ int CNAME(BLASLONG m, BLASLONG n, float alpha, bfloat16 *a, BLASLONG lda, bfloat
       }
 
       for (; i < m; ++i) {
-        y_ptr[iy] += alpha * a_ptr[i] * x_ptr[i];
+        y_ptr[iy] += alpha * vcvtah_f32_bf16(a_ptr[i]) * vcvtah_f32_bf16(x_ptr[i]);
       }
 
       iy += incy;
@@ -191,7 +186,7 @@ int CNAME(BLASLONG m, BLASLONG n, float alpha, bfloat16 *a, BLASLONG lda, bfloat
     temp = 0.0;
     ix = 0;
     for (i = 0; i < m; i++) {
-      temp += bf16_to_fp32(a[i]) * bf16_to_fp32(x[ix]);
+      temp += vcvtah_f32_bf16(a_ptr[i]) * vcvtah_f32_bf16(x_ptr[ix]);
       ix += incx;
     }
     if (beta == 0.0f) {