1.8 KiB
B plugin generator for VexRiscv
This repostory
This is a quick'n'dirty plugin generator to add a subset of the https://github.com/riscv/riscv-bitmanip extension to the https://github.com/SpinalHDL/VexRiscv core.
The generated plugin is for RV32 only. It doesn't yet support all instructions; missing instructions are:
- all instructions ending in 'W', as they are RV64-only
- BMAT*, as they are RV64-only
- CLMUL*
- BDEP/BEXT/BFP
- CRC32*
- Three-operands instrutioncs (CMIX, CMOV, FS[RL]*)
There is no support for 'partial' instruction - implementing only a subset of the functionality of one instruction. So grev is supported, but rev8 alone isn't. Subextension are defined without 'partial' instructions - so Zbb doesn't have rev8 or orc.B.
This has received limited testing in a https://github.com/litex-hub/linux-on-litex-vexriscv SoC. YMMV.
Also, the implementations of the instructions in SpinalHDL are written for tuncitonality, and not tuned or optimized in any way for performance/area/... (file usage.txt has some numbers).
How to use
There shouldn't be any dependency beyond gcc, g++, flex and bison. Instructions are defined in data_bitmanip.txt, look at the header of that file for the format - it should be fairly easy to add custom instructions if needed (as long as they are register-register, register-immediate, or unary and execute in one cycle).
The tool need an extension name, the data file and the list of instructions and/or sub-extension to support in the plugin:
./gen_plugin BitManipZbpZba data_bitmanip.txt Zba Zbb GORC GREV > BitManipZbbZba.scala
Will generate a plugin supporting Zbb (using the full version of grev and gorc) and Zba. You can use a star to say 'all supported instructions':
./gen_plugin BitManipAll data_bitmanip.txt '*' > BitManipAllPlugin.scala