llama.cpp/ggml/src/ggml-sycl/fusion.cpp

#include "fusion.hpp"

#include <algorithm>

// mul_mat(gate) + mul_mat(up) + GLU: graph shape and tensor properties only. Backend state
// (weight layout, split buffers, DMMV) is checked by ggml_sycl_mul_mat_glu_mmvq_fused().
static bool ggml_sycl_should_fuse_mul_mat_glu(const ggml_tensor * gate, const ggml_tensor * up,
                                              const ggml_tensor * glu) {
    // the fused epilogue implements these two; the rest fall back to the standalone GLU kernels
    const ggml_glu_op glu_op = ggml_get_glu_op(glu);
    if (glu_op != GGML_GLU_OP_SWIGLU && glu_op != GGML_GLU_OP_GEGLU) {
        return false;
    }

    // the kernel always treats src[0] as the activated operand and src[1] as the multiplier
    if (ggml_get_op_params_i32(glu, 1) /* swapped */) {
        return false;
    }

    const ggml_tensor * wu  = up->src[0];
    const ggml_tensor * wg  = gate->src[0];
    const ggml_tensor * act = up->src[1];

    // one set of block offsets and one quantized activation must serve both weights
    if (wu->type != wg->type || !ggml_are_same_shape(wu, wg) || !ggml_are_same_stride(wu, wg)) {
        return false;
    }
    if (act != gate->src[1]) {
        return false;
    }

    // only q4_K has a fused reorder GEMV so far, and it walks whole super-blocks
    if (wu->type != GGML_TYPE_Q4_K || wu->ne[0] % QK_K != 0) {
        return false;
    }

    // one 2D reorder-layout matrix in, a plain column stride out: no broadcast or padding
    if (!ggml_is_contiguous(wu) || !ggml_is_contiguous(wg) || !ggml_is_contiguous(act) ||
        !ggml_is_contiguous(glu)) {
        return false;
    }
    if (act->type != GGML_TYPE_F32 || glu->type != GGML_TYPE_F32) {
        return false;
    }
    if (act->ne[2] != 1 || act->ne[3] != 1 || wu->ne[2] != 1 || wu->ne[3] != 1) {
        return false;
    }
    // the kernel writes rows [0, wu->ne[1]) of each glu column, strided by glu->ne[0]
    if (glu->ne[0] != wu->ne[1] || glu->ne[1] != act->ne[1]) {
        return false;
    }
    // mat-vec only: one column per decoded token, up to the batch the reorder kernels cover
    if (act->ne[1] > MMVQ_MAX_BATCH_SIZE) {
        return false;
    }

    return true;
}

bool ggml_sycl_can_fuse(const ggml_cgraph * cgraph, int node_idx, std::initializer_list<enum ggml_op> ops,
                        std::initializer_list<enum ggml_unary_op> unary_ops) {
#ifndef NDEBUG
    const size_t num_unary = std::count(ops.begin(), ops.end(), GGML_OP_UNARY);
    GGML_ASSERT(unary_ops.size() == num_unary);
#endif

    if (!g_ggml_sycl_enable_fusion) {
        return false;
    }

    // gate and up are siblings, not a chain, so ggml_can_fuse cannot express this: use the
    // subgraph form with the GLU as the only materialised output.
    if (ops.size() == 3 && ops.begin()[0] == GGML_OP_MUL_MAT && ops.begin()[1] == GGML_OP_MUL_MAT &&
        ops.begin()[2] == GGML_OP_GLU) {
        if (!ggml_can_fuse_subgraph(cgraph, node_idx, ops, { node_idx + 2 })) {
            return false;
        }

        const ggml_tensor * glu  = cgraph->nodes[node_idx + 2];
        const ggml_tensor * gate = glu->src[0];
        const ggml_tensor * up   = glu->src[1];

        // don't assume which of the two mat-muls is the gate; infer it from the GLU's operands
        const bool ok = (gate == cgraph->nodes[node_idx] && up == cgraph->nodes[node_idx + 1]) ||
                        (gate == cgraph->nodes[node_idx + 1] && up == cgraph->nodes[node_idx]);
        if (!ok) {
            return false;
        }

        return ggml_sycl_should_fuse_mul_mat_glu(gate, up, glu);
    }

    if (!ggml_can_fuse(cgraph, node_idx, ops)) {
        return false;
    }

    if (ops.size() == 2 && ops.begin()[0] == GGML_OP_RMS_NORM && ops.begin()[1] == GGML_OP_MUL) {
        const ggml_tensor * rms_norm = cgraph->nodes[node_idx];
        const ggml_tensor * mul      = cgraph->nodes[node_idx + 1];

        GGML_ASSERT(rms_norm->src[0]->type == GGML_TYPE_F32);
        GGML_ASSERT(rms_norm->type == GGML_TYPE_F32);

        if (mul->src[0]->type != GGML_TYPE_F32 ||
            mul->src[1]->type != GGML_TYPE_F32 ||
            mul->type != GGML_TYPE_F32) {
            return false;
        }

        // if rms norm is the B operand, then we don't handle broadcast
        if (rms_norm == mul->src[1] && !ggml_are_same_shape(mul->src[0], rms_norm)) {
            return false;
        }

        const ggml_tensor * mul_w = (mul->src[0] == rms_norm) ? mul->src[1] : mul->src[0];
        // the fused kernel indexes the weight as mul[col], so it must span ncols contiguously
        if (mul_w->ne[0] != rms_norm->ne[0] || mul_w->nb[0] != ggml_type_size(mul_w->type)) {
            return false;
        }

        if (!ggml_is_contiguous_rows(mul->src[0]) || !ggml_is_contiguous_rows(mul->src[1])) {
            return false;
        }

        return true;
    }

    if (ops.size() == 2 && ops.begin()[0] == GGML_OP_UNARY && ops.begin()[1] == GGML_OP_MUL &&
        unary_ops.size() == 1) {
        const ggml_tensor * unary = cgraph->nodes[node_idx];
        const ggml_tensor * mul   = cgraph->nodes[node_idx + 1];

        const ggml_unary_op unary_op = ggml_get_unary_op(unary);
        if (unary_op != unary_ops.begin()[0]) {
            return false;
        }

        // the ops ggml_sycl_op_unary_mul_fused() has a kernel for
        if (unary_op != GGML_UNARY_OP_SILU && unary_op != GGML_UNARY_OP_SIGMOID &&
            unary_op != GGML_UNARY_OP_SOFTPLUS) {
            return false;
        }

        if (unary->type != GGML_TYPE_F32 && unary->type != GGML_TYPE_F16) {
            return false;
        }

        const ggml_tensor * other = (mul->src[0] == unary) ? mul->src[1] : mul->src[0];
        if (other->type != unary->type) {
            return false;
        }

        // one row stride per source comes from nb[1], so rows must be contiguous and equally
        // shaped; the destination is written flat, so it must be fully contiguous
        if (!ggml_is_contiguous_1(unary->src[0]) || !ggml_is_contiguous_1(other) ||
            !ggml_are_same_shape(other, unary) || !ggml_is_contiguous(mul)) {
            return false;
        }

        // the 32-bit fastdiv is inexact past 2^31; decline, the unfused path handles it
        if (ggml_nelements(mul) >= ((int64_t) 1 << 31)) {
            return false;
        }

        return true;
    }

    return false;
}