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Add Q4_K support to Hexagon Backend#54

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Add Q4_K support to Hexagon Backend#54
max-krasnyansky wants to merge 4 commits intomasterfrom
jules-310556977148145329-092f12b9

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The user requested adding Q4_K data type support to the Hexagon backend's MUL_MAT operation.

This PR implements:

  1. Type mappings and routing: Adds HTP_TYPE_Q4_K and routing in ggml-hexagon.cpp and matmul-ops.c.
  2. Repacking logic (ggml-hexagon.cpp): Q4_K quants are flat (128 bytes per 256 elements), along with 12 bytes of block scales. The repacking logic efficiently translates this into a highly optimized layout functionally identical to Q4_0x4x2. The 6-bit block scales are decompressed and pre-multiplied by d and dmin into arrays of 16-bit __fp16 values during repacking.
  3. HVX Vectorized Kernels (matmul-ops.c): Adds vec_dot_q4kx2_q8x4x2 block variants. Because Q4_K is asymmetric (d * q - m), the kernel computes sum(y) using an HVX dot product against a vector of 1s (Q6_Vb_vsplat_R(0x01)) to compute the offset offset subtraction, while efficiently reusing the native hvx_vec_load_q4x4x8_full and hvx_vec_rmpy_x8_full intrinsics for the main q * y dot product.
  4. HMX Support: HMX bypasses Q4_K due to the asymmetric scalar offset requirements that differ from the Q4_0 fast path.

PR created automatically by Jules for task 310556977148145329 started by @max-krasnyansky

Adds Q4_K type to `htp-ops.h`.
Implements `repack_row_q4kx2` to efficiently pack `Q4_K` into the `Q4_0x4x2` layout, computing fp16 scales `d` and `m` per 32 elements.
Implements `vec_dot_q4kx2_q8x4x2_1x1/2x1/2x2` in `matmul-ops.c` utilizing native HVX vectorized loads `hvx_vec_load_q4x4x8_full` and dot products `hvx_vec_rmpy_x8_full`, subtracting the asymmetric offset term efficiently without falling back to a scalar loop.
Ensures HMX path bypasses Q4_K to correctly compute using HVX.

Co-authored-by: max-krasnyansky <1380796+max-krasnyansky@users.noreply.github.com>
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google-labs-jules bot and others added 3 commits April 11, 2026 22:46
This commit adds full `Q4_K` data type support to the Hexagon backend's matrix multiplication kernels:

1. **Repacking (`ggml-hexagon.cpp`)**: `Q4_K` is seamlessly mapped to an internal flat representation. Because `Q4_K` is asymmetric, the 6-bit block scale `sc` and offset `m` terms are pre-multiplied by the super-block's global `d` and `dmin` constants (using native `__fp16` casts without `GGML_FP16_TO_FP32` macros), resulting in 16-byte `__fp16` arrays for scales and offsets per 256 elements, respectively. The layout now flawlessly mirrors the `Q4_0x4x2` scheme allowing full HVX instruction compatibility.
2. **Kernels (`matmul-ops.c`)**: `Q4_K` utilizes the `hvx_vec_load_q8x4x8_full` and `hvx_vec_load_q4x4x8_full` intrinsics for optimal `uint8_t` by `int8_t` memory alignment and fetching. The asymmetric minimum term `$m * \sum y$` is computed on the HVX coprocessor efficiently by running `hvx_vec_rmpy_x8_full(ones, vy_q)` alongside the standard `q * y` dot product, minimizing the need for loop-based unrolling. Leftover elements `nloe` are dynamically handled via `Q6_Q_vsetq_R` masking.
3. **Compatibility**: Removed `Q4_K` from the symmetric HMX fast path, explicitly falling back to the HVX routines. All temporary scratch files created during iterative development are purged from the repository.

Co-authored-by: max-krasnyansky <1380796+max-krasnyansky@users.noreply.github.com>
This commit completes `Q4_K` data type support for the Hexagon backend's matrix multiplication kernels:

1. **Repacking (`ggml-hexagon.cpp`)**: Seamlessly packs `Q4_K` to an internal flat layout optimized for vector fetches identically to `Q4_0x4x2`. The 6-bit block scale `sc` and offset `m` terms are pre-multiplied by `d` and `dmin` natively using `GGML_FP16_TO_FP32` and `GGML_FP32_TO_FP16` per host-side compilation standards.
2. **Kernels (`matmul-ops.c`)**: Avoids scalar fallbacks utilizing `hvx_vec_load_q4x4x8_full` natively to decompress `uint8_t` alignments. A 1s splat vector `Q6_Vb_vsplat_R(0x01)` operates against the activation inputs to correctly handle the asymmetric offset `m` using HVX reduction natively without performance loss. The leftover arrays `nloe` elegantly apply a bitmask logic `Q6_Q_vsetq_R(nloe / 8)` against `r0_dd` and `r0_mm`.
3. **Fixes**: Cleaned redundant Python scripts, avoided duplicate switches in C++, corrected the HVX vector initialization array field properties (`ones.v`), and restored proper logic masking parameters.

Co-authored-by: max-krasnyansky <1380796+max-krasnyansky@users.noreply.github.com>
This commit completes `Q4_K` data type support for the Hexagon backend's matrix multiplication kernels:

1. **Repacking (`ggml-hexagon.cpp`)**: Seamlessly packs `Q4_K` to an internal flat layout optimized for vector fetches identically to `Q4_0x4x2`. The 6-bit block scale `sc` and offset `m` terms are pre-multiplied by `d` and `dmin` natively using `GGML_FP16_TO_FP32` and `GGML_FP32_TO_FP16` per host-side compilation standards.
2. **Kernels (`matmul-ops.c`)**: Avoids scalar fallbacks utilizing `hvx_vec_load_q4x4x8_full` natively to decompress `uint8_t` alignments. A 1s splat vector `Q6_Vb_vsplat_R(0x01)` operates against the activation inputs to correctly handle the asymmetric offset `m` using HVX reduction natively without performance loss. The leftover arrays `nloe` elegantly apply a bitmask logic `Q6_Q_vsetq_R(nloe / 8)` against `r0_dd` and `r0_mm` using `hvx_vec_load_q8x4x8_full`.
3. **Fixes**: Cleaned redundant Python scripts, avoided duplicate switches in C++, corrected the HVX vector initialization array field properties (`ones.v`), corrected the signature of `vec_dot_q4kx2_q8x4x2_2x1`, and ensured `HTP_TYPE_Q4_K` is correctly integrated.

Co-authored-by: max-krasnyansky <1380796+max-krasnyansky@users.noreply.github.com>
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