This is the repository for the RISC-V Foundations Bitmanip Extension working group.

NOTE: These RISC-V Bitmanip instructions are a work in progress. These instructions and their specification may change before being accepted as a standard by the RISC-V Foundation and so it is highly likely that implementations made using this draft specification will not conform to the future standard.

See bitmanip-0.92.pdf for a pre-built version of the PDF spec document. The source of the PDF specification is in the texsrc directory with a script (bitmanip.sh) to build the PDF.

See the tools directory for build scripts for a compiler toolchain with RISC-V Bitmanip support. See rvintrin.h for compiler intrinsics.

The tests directory contains a test suite for the toolchain and bitmanip instructions.

The verilog directory includes various Verilog reference implementations.

The cproofs directory contains the reference C models and a few related formal proofs.

Included in this repository in the directory riscv-ovpsim is a version of the Imperas riscvOVPsim simulator that includes a full implementation of the RISC-V 32 & 64 Bit ISA specification and an implementation of these new bitmanip instructions.

To enable the new instructions, enable the B bit in the MISA register

riscvOVPsim.exe --override riscvOVPsim/cpu/add_Extensions=B

And in the log you will see it enabled, for example:

Info (Bit Manipulation) extB Version(0.92) November 08 2019

This simulation is instruction accurate, is provided as a pre-compiled binary, and the source of the new instructions in the model can be found in extB.c. If you want to make changes to the instructions, please contact the working group chair or Imperas.

NOTE the instruction behavior and decodes will change before they become part of the RISC-V open-standard ISA.

In order to produce the Specification pdf run the following command

$ make document

Please add an issue to this repository or email the normal bitmanip working group alias.

Many assembly tests are included (asmtests) that provide directed and generated tests for the new instructions. There is a simple framework to run the tests and compare them with a golden logfile.

To start, you need to set up the search path to include the path to a RISCV Compiler, eg:

$ export PATH=${PATH}:/home/tools/riscv-none-embed/bin

Also, you need a variable to define the canonical compiler prefix, eg:

$ export RISCV_PREFIX=riscv-none-embed-

And then you run the tests:

$ make runtest

This process is self-checking, and will report a set of passing/failing tests at the end.

To remove all generated files:

$ make clean

If you need changes to the instructions or want to make other additions or enhancements, please contact Imperas : [email protected]