ggml-cpu: optimize ggml_vec_dot_bf16 for Power9 (#18837)

ggml/src/ggml-cpu/simd-mappings.h

@@ -654,6 +654,14 @@ static inline void __avx_f32cx8_store(ggml_fp16_t *x, __m256 y) {
           vec_extract(x[0], 2) +               \
           vec_extract(x[0], 3);                \
 }
+#define GGML_F32x4_REDUCE_4(res, s0, s1, s2, s3)        \
+{                                                       \
+    vector float v = vec_add(vec_add(s0, s1),           \
+                             vec_add(s2, s3));          \
+    v = vec_add(v, vec_sld(v, v, 8));                   \
+    v = vec_add(v, vec_sld(v, v, 4));                   \
+    res += (ggml_float) vec_extract(v, 0);              \
+}
 
 #define GGML_F32_VEC        GGML_F32x4
 #define GGML_F32_VEC_ZERO   GGML_F32x4_ZERO
@@ -690,6 +698,29 @@ static inline unsigned char ggml_endian_byte(int i) {
                                    r[i - GGML_ENDIAN_BYTE(0)]), \
             0, p - GGML_F16_EPR)
 
+//BF16 POWER9
+#define GGML_BF16_STEP 16
+#define GGML_BF16_EPR  8
+
+#define GGML_BF16x8         vector unsigned short
+#define GGML_BF16x8_ZERO    vec_splats((unsigned short)0)
+#define GGML_BF16x8_LOAD(p) vec_xl(0, (const unsigned short *)(p))
+
+#define GGML_BF16_VEC          GGML_BF16x8
+#define GGML_BF16_VEC_ZERO     GGML_BF16x8_ZERO
+#define GGML_BF16_VEC_LOAD     GGML_BF16x8_LOAD
+#if defined(__LITTLE_ENDIAN__)
+#define GGML_BF16_TO_F32_LO(v) ((vector float) vec_mergel(GGML_BF16_VEC_ZERO, (v)))
+#define GGML_BF16_TO_F32_HI(v) ((vector float) vec_mergeh(GGML_BF16_VEC_ZERO, (v)))
+#else
+#define GGML_BF16_TO_F32_LO(v) ((vector float) vec_mergel((v), GGML_BF16_VEC_ZERO))
+#define GGML_BF16_TO_F32_HI(v) ((vector float) vec_mergeh((v), GGML_BF16_VEC_ZERO))
+#endif
+#define GGML_BF16_FMA_LO(acc, x, y) \
+    (acc) = GGML_F32x4_FMA((acc), GGML_BF16_TO_F32_LO(x), GGML_BF16_TO_F32_LO(y))
+#define GGML_BF16_FMA_HI(acc, x, y) \
+    (acc) = GGML_F32x4_FMA((acc), GGML_BF16_TO_F32_HI(x), GGML_BF16_TO_F32_HI(y))
+
 #elif defined(__wasm_simd128__)
 
 #define GGML_SIMD

ggml/src/ggml-cpu/vec.cpp

@@ -237,6 +237,24 @@ void ggml_vec_dot_bf16(int n, float * GGML_RESTRICT s, size_t bs, ggml_bf16_t *
     sumf += __riscv_vfmv_f_s_f32m1_f32(redsum);
 
 #endif
+#if defined(__POWER9_VECTOR__)
+    const int np = (n & ~(GGML_BF16_STEP - 1));
+    if (np > 0) {
+        GGML_F32_VEC sum[4] = {GGML_F32_VEC_ZERO};
+        for (; i < np; i += GGML_BF16_STEP) {
+            GGML_BF16_VEC vx0 = GGML_BF16_VEC_LOAD(x + i);
+            GGML_BF16_VEC vx1 = GGML_BF16_VEC_LOAD(x + i + 8);
+            GGML_BF16_VEC vy0 = GGML_BF16_VEC_LOAD(y + i);
+            GGML_BF16_VEC vy1 = GGML_BF16_VEC_LOAD(y + i + 8);
+            GGML_BF16_FMA_LO(sum[0], vx0, vy0);
+            GGML_BF16_FMA_HI(sum[1], vx0, vy0);
+            GGML_BF16_FMA_LO(sum[2], vx1, vy1);
+            GGML_BF16_FMA_HI(sum[3], vx1, vy1);
+        }
+        GGML_F32x4_REDUCE_4(sumf, sum[0], sum[1], sum[2], sum[3]);
+    }
+#endif
+
     for (; i < n; ++i) {
         sumf += (ggml_float)(GGML_BF16_TO_FP32(x[i]) *
                              GGML_BF16_TO_FP32(y[i]));