Felix-Gong opened a new pull request, #3332: URL: https://github.com/apache/brpc/pull/3332
## Summary - Implement CRC32C using RISC-V Zvbc vector carry-less multiplication (`vclmul`/`vclmulh` RVV intrinsics) - Processes 4 lanes of 128-bit folding per iteration (64 bytes), with 4-to-1 lane reduction and Barrett reduction - Add `WITH_RISCV_ZVBC` cmake option - Fix macro guards to support `__riscv_zvbc` without `__riscv_zvbc` (Zvbc implies Zbc per spec, but compiler may not define both) - Zvbc preferred over Zbc in `Choose_Extend()` for higher throughput ## Background This extends the existing Zbc scalar CRC32C optimization (merged in #3312) with vector support. The implementation follows the same 128-bit folding + Barrett reduction approach used in x86 SSE4.2, ARM PMULL, and Hadoop's RISC-V CRC32C PRs (#7903, #8031, #8371). ## Key implementation details - With VLEN=128, each vector register holds 2×64-bit elements, so 2 vector register pairs = 128-bit lane - Fold constants: k1=0x740eef02 (x^256 mod P), k2=0x9e4addf8 (x^320 mod P), k3=0xf20c0dfe (x^128 mod P), k4=0x493c7d27 (x^192 mod P) - Cross-element XOR via scalar extraction (practical for VLEN=128 with only 2 elements) - Barrett reduction uses scalar `clmul`/`clmulh` (Zbc instructions, available when Zvbc is present) ## Testing Verified on QEMU with `-cpu rv64,zvbc=true,v=true,vlen=128`: - All RFC 3720 B.4 test vectors pass - Large data (64/128/256/1024 bytes) results match x86 SSE4.2 reference values - Extend (chained CRC) works correctly - Zvbc and Zbc paths produce identical results ## Build ```bash cmake -DWITH_RISCV_ZVBC=ON .. ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
