rawdog-jit-asm

name: rawdog-jit-asm description: Author and wire RawDog JIT NASM blobs for PerfectHash online (x64), including sentinel patching, CMake header generation, and validation against LLVM/offline outputs. Use when adding or modifying RawDog JIT assembly for a hash function or when comparing compiler output for reference.

RawDog JIT Assembly

Overview

Author x64 NASM RawDog JIT Index() blobs, wire them into the RawDog backend, and validate correctness against SlowIndex and offline compiler output.

Workflow

1. Identify the exact index algorithm

   • Inspect src/PerfectHash/PerfectHashTableHashEx.c for the hash math.
   • Inspect src/PerfectHash/ChmOnline01.c (BuildChm01Index* switch) for the actual index logic (masking, table loads, index mask).

2. Create the NASM blob

   • Copy style and conventions from src/PerfectHash/PerfectHashTableFastIndexEx_x64_01.asm and existing RawDog blobs.
   • Use the RawDog sentinel values for Assigned, Seed1, Seed2, Seed3Byte1, Seed3Byte2, HashMask, and IndexMask as needed.
   • Ensure each sentinel appears exactly once in the data block; load once into a register and reuse if needed.

3. Generate the embedded header

   • Add a CMake add_custom_command() to run nasm -> objcopy -> scripts/generate_rawdog_jit_header.py.
   • Append the generated header to Private_Header_Files in src/PerfectHash/CMakeLists.txt.

4. Wire the backend

   • Update src/PerfectHash/ChmOnline01RawDog.c to select the new blob and patch sentinels.
   • Keep RawDog constrained to supported flags (scalar Index32 only for now).

5. Validate

   • Add or update a RawDog unit test in tests/PerfectHashOnlineTests.cpp.
   • Run the offline compiler path and disassemble the resulting .so for reference (see references/offline-compile-and-disasm.md).

References

• Offline build + disassembly workflow: references/offline-compile-and-disasm.md