| Issue |
144150
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| Summary |
[RISCV] LLVM doesn't support B extension in march
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| Labels |
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| Assignees |
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| Reporter |
Timmmm
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LLVM used to support the `B` extension as part of the RISC-V `-march` ISA string, but it was dropped a few years ago in ae116f43ff140edfae166370ab6bc9ae3f556710.
I wasn't working on RISC-V then so I'm not sure what happened, but today, the B extension is ratified. [Supporting `B` implies `Zba`, `Zbb` and `Zbs`](https://riscv-specs.timhutt.co.uk/spec/20240411/unpriv-isa-asciidoc.html#bits) which are subsets of it.
> The B standard extension comprises instructions provided by the Zba, Zbb, and Zbs extensions.
Currently if you try to use a `march` with B it says `clang: error: invalid arch name 'rv64imafdcbv_zicbom_zicboz_zicntr_zicond_zicsr_zifencei_zihpm_zimop0p1_zawrs_zfa_zfh_zca_zcb_zcd_zcmop0p2_zbc_zbkb_zbkc_zbkx_zknd_zkne_zknh_zkr_zksed_zksh_zvbb_zvbc_zvkg_zvkned_zvknha_zvknhb_zvksh', unsupported standard user-level extension 'b'`
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