Update RISC-V ISA configs #46483
Description
Is your enhancement proposal related to a problem? Please describe.
From https://www.mail-archive.com/[email protected]/msg430287.html:
From version 2.38, binutils default to ISA spec version 20191213. This
means that the csr read/write (csrr*/csrw*) instructions and fence.i
instruction has separated from theIextension, become two standalone
extensions: Zicsr and Zifencei.
The csr* instructions are no longer part of the "I" extension and require a separate extension called "Zicsr" to be specified to the -march flag.
Without this, build will fail with the following error message:
/home/runner/work/sdk-ng/sdk-ng/zephyrproject/zephyr/soc/riscv/riscv-privilege/common/soc_irq.S: Assembler messages:
/home/runner/work/sdk-ng/sdk-ng/zephyrproject/zephyr/soc/riscv/riscv-privilege/common/soc_irq.S:31: Error: unrecognized opcode `csrrc t1,mip,t0'
/home/runner/work/sdk-ng/sdk-ng/zephyrproject/zephyr/soc/riscv/riscv-privilege/common/soc_irq.S:50: Error: unrecognized opcode `csrr t0,mcause'
For more details, refer to the following log attempting to build a Zephyr RISC-V target using the Binutils 2.38:
https://github.com/zephyrproject-rtos/sdk-ng/runs/6862707569?check_suite_focus=true#step:11:226
Describe the solution you'd like
Add the ISA extension Kconfig symbols for the new (missing) extensions:
- Zicsr
- Zifencei
- Zba, Zbb, Zbc, Zbs (formerly the "B" extension which, to my knowledge, is no longer a thing)
Describe alternatives you've considered
We could build the Binutils targeting an older ISA spec (for example, with --with-isa-spec=2.2), but this does not reflect the latest RISC-V standard and will likely become unmaintainable in the near future (it is already sort of deprecated).
Additional context
Discovered while upgrading the version of the Binutils included in the Zephyr SDK from 2.35.1 to 2.38 -- this enhancement will be required in order to support the upcoming Zephyr SDK 0.15.0 release.