b10871

vulkan: add dedicated iq4_xs mat-vec shader (#28426)

• vulkan: add dedicated iq4_xs mat-vec shader

Dedicated mul_mat_vec_iq4_xs for the dmmv path, replacing the generic fallback. ~+6-17% token generation on RDNA4 depending on model.

Assisted-by: Pi agent with Qwen3.8 27B

• vulkan iq4_xs: remove dead n_it unroll branch

Remove the n_it <= 8 experimental branch that attempted to fully unroll
the block loop. Since n_it is a runtime value, [[unroll]] is ignored by
the compiler, making both branches equivalent. Kept the simple loop
matching mul_mat_vec_iq3_s.comp.

Website:

• https://llama.app

Attestations:

• https://github.com/ggml-org/llama.cpp/attestations/46172644

macOS/iOS:

• macOS Apple Silicon (arm64)
• macOS Apple Silicon (arm64, KleidiAI enabled) DISABLED
• macOS Intel (x64)
• iOS XCFramework

Linux:

• Ubuntu x64 (CPU)
• Ubuntu arm64 (CPU)
• Ubuntu s390x (CPU)
• Ubuntu x64 (Vulkan)
• Ubuntu arm64 (Vulkan)
• Ubuntu x64 (ROCm 10.0)
• Ubuntu x64 (OpenVINO)
• Ubuntu x64 (SYCL FP32)
• Ubuntu x64 (SYCL FP16)

Android:

• Android arm64 (CPU)

Windows:

• Windows x64 (CPU)
• Windows arm64 (CPU)
• Windows arm64 (OpenCL Adreno)
• Windows x64 (CUDA 12) - CUDA 12.4 DLLs
• Windows x64 (CUDA 13) - CUDA 13.3 DLLs
• Windows arm64 (CUDA 13) (preview) - CUDA 13.4 DLLs
• Windows x64 (Vulkan)
• Windows x64 (OpenVINO)
• Windows x64 (SYCL)
• Windows x64 (ROCm 10.0)

openEuler:

• DISABLED
• openEuler x86 (310p)
• openEuler x86 (910b, ACL Graph)
• openEuler aarch64 (310p)
• openEuler aarch64 (910b, ACL Graph)

UI:

• UI