Feature hexagon l2 norm (#22816)

* L2_NORM Updates

* Addressed PR Comments

* ggml-hexagon: add L2_NORM HVX kernel for Hexagon backend

* hex-unary: remove supported_unary_nc since the outer loop is the same for all unary ops

---------

Co-authored-by: Max Krasnyansky <maxk@qti.qualcomm.com>

ggml/src/ggml-hexagon/ggml-hexagon.cpp

@@ -2420,8 +2420,8 @@ static bool ggml_hexagon_supported_unary(const struct ggml_hexagon_session * ses
         return false;
     }
 
-    // TODO: add support for non-contiguous elements within a row
+    // dst must be contiguous; src0 may be non-contiguous
-    if (!ggml_is_contiguous_rows(src0) || !ggml_is_contiguous_rows(dst)) {
+    if (!ggml_is_contiguous(dst)) {
         return false;
     }
 
@@ -2791,6 +2791,7 @@ static htp_op_code op_remap_to_htp(const ggml_tensor * t) {
         case GGML_OP_SET_ROWS:       return HTP_OP_SET_ROWS;
         case GGML_OP_SUM_ROWS:       return HTP_OP_SUM_ROWS;
         case GGML_OP_ARGSORT:        return HTP_OP_ARGSORT;
+        case GGML_OP_L2_NORM:        return HTP_OP_L2_NORM;
         case GGML_OP_RMS_NORM:       return HTP_OP_RMS_NORM;
         case GGML_OP_SCALE:          return HTP_OP_SCALE;
         case GGML_OP_SQR:            return HTP_OP_SQR;
@@ -3253,6 +3254,10 @@ static bool ggml_backend_hexagon_device_supports_op(ggml_backend_dev_t dev, cons
             supp = ggml_hexagon_supported_add_id(sess, op);
             break;
 
+        case GGML_OP_L2_NORM:
+            supp = ggml_hexagon_supported_unary(sess, op);
+            break;
+
         case GGML_OP_RMS_NORM:
         case GGML_OP_SCALE:
             supp = ggml_hexagon_supported_unary(sess, op);

ggml/src/ggml-hexagon/htp/htp-ops.h

@@ -83,6 +83,8 @@ enum htp_op_code {
     HTP_OP_FILL,
     HTP_OP_DIAG,
     HTP_OP_SOLVE_TRI,
+    HTP_OP_L2_NORM,
+
     HTP_OP_INVALID
 };
 

ggml/src/ggml-hexagon/htp/main.c

@@ -542,6 +542,7 @@ static int execute_op(struct htp_ops_context * octx) {
         case HTP_OP_UNARY_SIGMOID:
         case HTP_OP_UNARY_NEG:
         case HTP_OP_UNARY_EXP:
+        case HTP_OP_L2_NORM:
             return op_unary(octx);
 
         case HTP_OP_UNARY_SILU:

ggml/src/ggml-hexagon/htp/unary-ops.c

@@ -298,6 +298,81 @@ static void softplus_f32(const float * restrict src,
     }
 }
 
+// --- L2_NORM HVX kernel ---
+// Computes y[i] = x[i] / fmax(sqrt(sum(x[j]^2)), epsilon) for each row.
+// scale = 1/fmax(sqrt(sum), epsilon) is computed entirely in HVX registers
+// using rsqrt + inverse to avoid scalar extraction.
+static void hvx_fast_l2_norm_f32(const uint8_t * restrict src,
+                                 uint8_t * restrict dst,
+                                 uint8_t * restrict pad,
+                                 const int num_elems,
+                                 float     epsilon) {
+    (void)pad;
+
+    const HVX_Vector * restrict v_src = (HVX_Vector *) src;
+    HVX_Vector * restrict v_dst       = (HVX_Vector *) dst;
+
+    HVX_Vector sum_v = hvx_vec_splat_f32(0.0f);
+
+    const int nvec = num_elems / VLEN_FP32;
+    const int nloe = num_elems % VLEN_FP32;
+
+    #pragma unroll(4)
+    for (int i = 0; i < nvec; i++) {
+        HVX_Vector v1 = v_src[i];
+        HVX_Vector sq = Q6_Vqf32_vmpy_VsfVsf(v1, v1);
+        sum_v         = Q6_Vqf32_vadd_Vqf32Vqf32(sum_v, sq);
+    }
+
+    // Include tail elements in the sum-of-squares using a predicate mask
+    if (nloe > 0) {
+        HVX_VectorPred bmask = Q6_Q_vsetq_R(nloe * 4);
+        HVX_Vector v1 = Q6_V_vand_QV(bmask, v_src[nvec]);
+        HVX_Vector sq = Q6_Vqf32_vmpy_VsfVsf(v1, v1);
+        sum_v         = Q6_Vqf32_vadd_Vqf32Vqf32(sum_v, sq);
+    }
+
+    // Compute scale = 1/fmax(sqrt(sum), epsilon) entirely in HVX registers.
+    // hvx_vec_rsqrt_f32 + hvx_vec_inverse_f32 avoids scalar extraction.
+    HVX_Vector sum_sf    = hvx_vec_reduce_sum_f32(Q6_Vsf_equals_Vqf32(sum_v));
+    HVX_Vector rsqrt_v   = hvx_vec_rsqrt_f32(sum_sf);              // 1/sqrt(sum)
+    HVX_Vector sqrt_v    = hvx_vec_inverse_f32(rsqrt_v);            // sqrt(sum)
+    HVX_Vector epsilon_v = hvx_vec_splat_f32(epsilon);
+    HVX_Vector denom_v   = Q6_Vsf_vmax_VsfVsf(sqrt_v, epsilon_v);  // fmax(sqrt(sum), epsilon)
+    HVX_Vector scale_v   = hvx_vec_inverse_f32(denom_v);            // 1/fmax(sqrt(sum), epsilon)
+
+    #pragma unroll(4)
+    for (int i = 0; i < nvec; i++) {
+        HVX_Vector v1 = v_src[i];
+        v_dst[i]      = Q6_Vsf_equals_Vqf32(Q6_Vqf32_vmpy_VsfVsf(v1, scale_v));
+    }
+
+    if (nloe > 0) {
+        HVX_VectorPred bmask = Q6_Q_vsetq_R(nloe * 4);
+        HVX_Vector v1 = Q6_V_vand_QV(bmask, v_src[nvec]);
+        HVX_Vector result = Q6_Vsf_equals_Vqf32(Q6_Vqf32_vmpy_VsfVsf(v1, scale_v));
+        hvx_vec_store_a(&v_dst[nvec], nloe * 4, result);
+    }
+}
+
+static void l2_norm_f32(const float * restrict src,
+                        float * restrict dst,
+                        uint8_t * restrict spad,
+                        const uint32_t num_rows,
+                        const uint32_t row_elems,
+                        const size_t   row_size,
+                        int32_t *      op_params) {
+    float epsilon = 0.f;
+    memcpy(&epsilon, op_params, sizeof(float));
+
+    for (uint32_t ir = 0; ir < num_rows; ir++) {
+        const float * restrict src_f = (const float *)((const uint8_t *)src + (ir * row_size));
+        float * restrict dst_f       = (float *)((uint8_t *)dst + (ir * row_size));
+
+        hvx_fast_l2_norm_f32((const uint8_t *)src_f, (uint8_t *)dst_f, spad, row_elems, epsilon);
+    }
+}
+
 static void unary_job_f32_per_thread(unsigned int nth, unsigned int ith, void * data) {
     const struct htp_unary_context * uctx = (const struct htp_unary_context *) data;
     struct htp_ops_context * octx = uctx->octx;
@@ -402,6 +477,9 @@ static void unary_job_f32_per_thread(unsigned int nth, unsigned int ith, void *
             case HTP_OP_UNARY_SOFTPLUS:
                 softplus_f32(src0_spad, dst_spad, NULL, block_size, ne0, src0_row_size_aligned, op_params);
                 break;
+            case HTP_OP_L2_NORM:
+                l2_norm_f32(src0_spad, dst_spad, NULL, block_size, ne0, src0_row_size_aligned, op_params);
+                break;
             default:
                 break;
         }
@@ -469,6 +547,9 @@ static int execute_op_unary_f32(struct htp_ops_context * octx) {
         case HTP_OP_UNARY_SOFTPLUS:
             op_type = "softplus-f32";
             break;
+        case HTP_OP_L2_NORM:
+            op_type = "l2norm-f32";
+            break;
 
         default:
             FARF(ERROR, "Unsupported unary Op %u\n", octx->op);