b12207

ggml-cuda : add d_state=64 fast path to SSM_SCAN kernel (#31818)

Zamba2 and similar architectures use a state size of 64 in their
recurrent-scan step, which fell outside the GPU kernel's existing
fast paths (96, 128, 256). Every scan step was falling back to CPU,
bottlenecking generation to 6-7 tok/s against the 50-70 tok/s band
other architectures achieve on the same hardware.

Add a 4th template instantiation for d_state=64, following the
existing pattern; no change to the underlying math. Verified against
the existing CPU-reference correctness harness with 3 new test cases
built from Zamba2's real hyperparameters (28/28 passing).

Measured ~35% throughput improvement (11 -> 15.1 tok/s) on Zamba2-7B-
Instruct. Full parity with other architectures not yet reached - a
separate, unrelated fraction of scan calls (~28%) still falls back to
CPU for a cause not yet diagnosed.

Assisted-by: Claude Sonnet 5

Co-authored-by: Sargentmajord 331229907+sargentmajord@users.noreply.github.com

Website:

• https://llama.app

Attestations:

• https://github.com/ggml-org/llama.cpp/attestations/65059042

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 24.04 s390x (CPU)
• Ubuntu 26.04 s390x (CPU)
• Ubuntu 26.04 s390x (zDNN)
• Ubuntu x64 (Vulkan)
• Ubuntu arm64 (Vulkan)
• Ubuntu x64 (CUDA 12) - CUDA 12.8 libraries
• Ubuntu x64 (CUDA 13) - CUDA 13.5 libraries
• Ubuntu arm64 (CUDA 13) - CUDA 13.5 libraries
• Ubuntu x64 (ROCm 10.0)
• Ubuntu x64 (OpenVINO)
• Ubuntu x64 (SYCL FP32)
• Ubuntu x64 (SYCL FP16)
• Linux arm64 (Snapdragon: CPU, Adreno GPU, Hexagon NPU) - setup guide

Android:

• Android arm64 (CPU)
• Android arm64 (Snapdragon: CPU, Adreno GPU, Hexagon NPU) - setup guide

Windows:

• Windows x64 (CPU)
• Windows arm64 (CPU)
• Windows arm64 (OpenCL Adreno)
• Windows x64 (CUDA 12) - CUDA 12.4 DLLs
• Windows x64 (CUDA 13) - CUDA 13.5 DLLs
• Windows arm64 (CUDA 13) - CUDA 13.5 DLLs
• Windows x64 (Vulkan)
• Windows arm64 (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