ggml-org/llama.cpp b10891

on GitHub

vulkan: fall back to shared-memory reduction for dmmv on PowerVR (#28341)

The Imagination proprietary Vulkan compiler returns VK_ERROR_UNKNOWN from
vkCreateComputePipelines for every dequant mul_mat_vec shader built with the
subgroup-only reduction that requires a subgroup size >= 16. That covers the
k-quants, the i-quants, TQ2_0, MXFP4 and NVFP4. ggml rethrows, so the first
generated token of any such model kills the process.

Reproduced on a Pixel 11 Pro (PowerVR C-Series CXTP-48-1536 MC1, driver
1.662.3024, subgroup size 128, min 32, max 128). The failure is independent of
subgroup size: 32, 64 and 128 all fail, as does dropping the full-subgroups
flag and the required-subgroup-size pNext. The legacy quants, which use the
plain subgroup reduction, compile and run fine.

The shared-memory reduction variant compiles and matches the CPU reference for
q2_K, q3_K, q4_K, q5_K and q6_K. The hybrid variant also compiles but costs
27% of token throughput (3.78 vs 5.20 t/s on Qwen3.5-2B-Q4_K_M).