Add AMD ROCm/HIP Support and Strix Halo Optimizations

[AyaSakura-comp]

Pull Request Description: Add AMD ROCm/HIP Support and Strix Halo Optimizations

Overview

This PR introduces a complete AMD ROCm/HIP backend to DwarfStar 4, optimized specifically for hardware with unified memory architectures like the AMD Strix Halo (gfx1151). It migrates the project from its original CUDA dependency to a portable HIP implementation while maintaining functional parity and performance.

Key Changes

1. ROCm/HIP Backend Migration:
   • Ported ds4_cuda.cu to ds4_hip.cpp and transitioned all symbol dependencies from CUDA/cuBLAS to HIP/hipBLAS.
   • Updated the Makefile to detect and support the ROCm stack using hipcc.
2. Strix Halo / HSA Optimizations:
   • Zero-Copy Memory Access: Configured the engine to use HSA direct access (Zero-Copy) by default on AMD hardware. This avoids duplicating 83+ GiB of model weights in system RAM, significantly reducing memory overhead.
   • Vectorized Kernels: Optimized F16 and F32 GEMV kernels using vectorized loads and warp-shuffle reductions for improved decoding throughput.
   • Hardware Intrinsics: Replaced scalar loops with AMD-specific hardware dot-product intrinsics (v_dot4_i32_i8).
3. Unified Tooling:
   • Added build.sh: A one-click script for ROCm compilation.
   • Added rocm_start_server.sh: A unified script that handles stale process cleanup, system cache flushing, and optimized server launch.
4. Verification:
   • Successfully validated with the rocm-regression long-context smoke test.
   • End-to-end testing performed using DeepSeek-V4-Flash Q2-imatrix weights.

Performance Benchmarks (AMD Strix Halo / Radeon Graphics)

• Decoding Speed: 8.09 – 13.24 tokens/sec (Non-MTP, Zero-Copy mode).
• Prefill Latency: ~4.45s for short prompts (post-warmup).
• Startup: ~16s weight warmup for 83.60 GiB mapping.

How to Test

1. Build: ./build.sh
2. Start: ./rocm_start_server.sh
3. Verify:

   curl -X POST http://127.0.0.1:8000/v1/chat/completions \
       -H "Content-Type: application/json" \
       -d '{
           "model": "ds4flash",
           "messages": [{"role": "user", "content": "Hello, how are you?"}],
           "max_tokens": 50
       }'

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Summary of Work Done

• Full Backend Port: Replaced all CUDA/cuBLAS APIs with HIP/hipBLAS equivalents.
• Environmental Cleanup: Renamed all CUDA-specific environment variables to DS4_HIP_* (e.g., DS4_HIP_PREFILL_CHUNK).
• Driver Compatibility: Added robust hipHostRegister fallbacks for diverse ROCm driver environments.
• Unified Startup Flow: Fused cleanup and server launch into a single, reliable maintenance script.
• Documentation Integrity: Updated README.md with dedicated ROCm onboarding instructions.