RISC-V: Extension Updates (including document references) #2002

a4lg · 2025-09-17T02:43:38Z

This PR updates documentation links and fixes minor issues:

Non-existent zb is removed (b exists but not stabilized yet).
Wrong link for the zbkc target feature is fixed.
Implication from the zbc target feature is updated (reflects the behavior of rustc_target: Adjust RISC-V feature implication rust#140139).

Note that this PR itself does not attempt to stabilize any of new extensions (target features) but makes the documentation more solid.

a4lg · 2025-09-17T02:44:24Z

Note that, this PR is separated from #1987 (which includes stabilization of new extensions) for early adoption of the non-stabilization part.
~~The next submission of~~ #1987 ~~will be~~ is now based on this PR.

The `Zb` extension does not exist and we instead have the `B` extension which is a superset of the three subextensions: `Zba`, `Zbb` and `Zbs`. For now (since `B` extension is not stabilized on Rust), this commit just removes `Zb`.

This is the latest ratified ISA Manual version and more importantly, some individual documents are merged into this. So, this commit consistently use this Manual (this version) where possible. Along with this, this commit substitutes link IDs from `rv-zb-*` to `rv-*` because `rv-zb-*` will look like the different document (bit-manipulation) is referenced.

rust-lang/rust#140139 changed the target feature implication without updating the Reference. That change is came from the fact that the Zbc extension is a functional superset of the Zbkc extension. This commit fixes this issue. Appendix - List of all Zbkc / Zbc instructions: * `clmul` (Zbkc / Zbc) * `clmulh` (Zbkc / Zbc) * `clmulr` (Zbc only)

ehuss · 2025-09-23T23:00:48Z

@Amanieu can you take a look at this?
Also ping @taiki-e since you approved #2005. I'm not sure if you're interested in reviewing these.

We need an appropriate group of people to ping for RISC-V.

a4lg · 2025-09-24T01:26:28Z

@ehuss This is a strict subset of #1987 (which contains all of this PR (4 commits) + one stabilization commit) and it seems @Amanieu approved that superset.

So IIUC, @Amanieu effectively approved all of the changes here.

ehuss

Thanks!

Update books ## rust-lang/book 1 commits in 33f1af40cc44dde7e3e892f7a508e6f427d2cbc6..1d7c3e6abec2d5a9bfac798b29b7855b95025426 2025-09-28 21:24:16 UTC to 2025-09-28 21:24:16 UTC - Chunk of chapters from copyedit (rust-lang/book#4506) ## rust-lang/edition-guide 1 commits in aa6ce337c0adf7a63e33960d184270f2a45ab9ef..e2ed891f00361efc26616d82590b1c85d7a8920e 2025-10-01 17:11:54 UTC to 2025-10-01 17:11:54 UTC - link to never type fallback lint as deny by default (rust-lang/edition-guide#377) ## rust-lang/nomicon 1 commits in f17a018b9989430967d1c58e9a12c51169abc744..23fc2682f8fcb887f77d0eaabba708809f834c11 2025-09-24 10:10:31 UTC to 2025-09-24 10:10:31 UTC - a typo in ffi.md (rust-lang/nomicon#502) ## rust-lang/reference 13 commits in cc7247d8dfaef4c39000bb12c55c32ba5b5ba976..e11adf6016a362766eea5a3f9832e193994dd0c8 2025-09-29 00:55:42 UTC to 2025-09-23 23:33:32 UTC - const functions: separate rule about users and rule about what is allowed in such functions (rust-lang/reference#2013) - use "tuple enum variant" more consistently (rust-lang/reference#2015) - Remove caveats related to `format_args!` expansion (rust-lang/reference#2017) - RISC-V: Extension Updates (including document references) (rust-lang/reference#2002) - Move inferred sentence to an example block (rust-lang/reference#2019) - Add triagebot range-diff feature (rust-lang/reference#2011) - use AND when searching for multiple terms (rust-lang/reference#2016) - enumerations.md: fix pluralisation (rust-lang/reference#2014) - const_eval.md: use sentence case for section title, for consistency (rust-lang/reference#2012) - destructors.md: improve readability by adding pauses (rust-lang/reference#2007) - RISC-V: Add vector state registers (rust-lang/reference#2005) - destructors.md: point to core:: instead of std:: (rust-lang/reference#2006) - Create Whitespace grammar productions (rust-lang/reference#1991)

Rollup merge of #147236 - rustbot:docs-update, r=ehuss Update books ## rust-lang/book 1 commits in 33f1af40cc44dde7e3e892f7a508e6f427d2cbc6..1d7c3e6abec2d5a9bfac798b29b7855b95025426 2025-09-28 21:24:16 UTC to 2025-09-28 21:24:16 UTC - Chunk of chapters from copyedit (rust-lang/book#4506) ## rust-lang/edition-guide 1 commits in aa6ce337c0adf7a63e33960d184270f2a45ab9ef..e2ed891f00361efc26616d82590b1c85d7a8920e 2025-10-01 17:11:54 UTC to 2025-10-01 17:11:54 UTC - link to never type fallback lint as deny by default (rust-lang/edition-guide#377) ## rust-lang/nomicon 1 commits in f17a018b9989430967d1c58e9a12c51169abc744..23fc2682f8fcb887f77d0eaabba708809f834c11 2025-09-24 10:10:31 UTC to 2025-09-24 10:10:31 UTC - a typo in ffi.md (rust-lang/nomicon#502) ## rust-lang/reference 13 commits in cc7247d8dfaef4c39000bb12c55c32ba5b5ba976..e11adf6016a362766eea5a3f9832e193994dd0c8 2025-09-29 00:55:42 UTC to 2025-09-23 23:33:32 UTC - const functions: separate rule about users and rule about what is allowed in such functions (rust-lang/reference#2013) - use "tuple enum variant" more consistently (rust-lang/reference#2015) - Remove caveats related to `format_args!` expansion (rust-lang/reference#2017) - RISC-V: Extension Updates (including document references) (rust-lang/reference#2002) - Move inferred sentence to an example block (rust-lang/reference#2019) - Add triagebot range-diff feature (rust-lang/reference#2011) - use AND when searching for multiple terms (rust-lang/reference#2016) - enumerations.md: fix pluralisation (rust-lang/reference#2014) - const_eval.md: use sentence case for section title, for consistency (rust-lang/reference#2012) - destructors.md: improve readability by adding pauses (rust-lang/reference#2007) - RISC-V: Add vector state registers (rust-lang/reference#2005) - destructors.md: point to core:: instead of std:: (rust-lang/reference#2006) - Create Whitespace grammar productions (rust-lang/reference#1991)

Update books ## rust-lang/book 1 commits in 33f1af40cc44dde7e3e892f7a508e6f427d2cbc6..1d7c3e6abec2d5a9bfac798b29b7855b95025426 2025-09-28 21:24:16 UTC to 2025-09-28 21:24:16 UTC - Chunk of chapters from copyedit (rust-lang/book#4506) ## rust-lang/edition-guide 1 commits in aa6ce337c0adf7a63e33960d184270f2a45ab9ef..e2ed891f00361efc26616d82590b1c85d7a8920e 2025-10-01 17:11:54 UTC to 2025-10-01 17:11:54 UTC - link to never type fallback lint as deny by default (rust-lang/edition-guide#377) ## rust-lang/nomicon 1 commits in f17a018b9989430967d1c58e9a12c51169abc744..23fc2682f8fcb887f77d0eaabba708809f834c11 2025-09-24 10:10:31 UTC to 2025-09-24 10:10:31 UTC - a typo in ffi.md (rust-lang/nomicon#502) ## rust-lang/reference 13 commits in cc7247d8dfaef4c39000bb12c55c32ba5b5ba976..e11adf6016a362766eea5a3f9832e193994dd0c8 2025-09-29 00:55:42 UTC to 2025-09-23 23:33:32 UTC - const functions: separate rule about users and rule about what is allowed in such functions (rust-lang/reference#2013) - use "tuple enum variant" more consistently (rust-lang/reference#2015) - Remove caveats related to `format_args!` expansion (rust-lang/reference#2017) - RISC-V: Extension Updates (including document references) (rust-lang/reference#2002) - Move inferred sentence to an example block (rust-lang/reference#2019) - Add triagebot range-diff feature (rust-lang/reference#2011) - use AND when searching for multiple terms (rust-lang/reference#2016) - enumerations.md: fix pluralisation (rust-lang/reference#2014) - const_eval.md: use sentence case for section title, for consistency (rust-lang/reference#2012) - destructors.md: improve readability by adding pauses (rust-lang/reference#2007) - RISC-V: Add vector state registers (rust-lang/reference#2005) - destructors.md: point to core:: instead of std:: (rust-lang/reference#2006) - Create Whitespace grammar productions (rust-lang/reference#1991)

rustbot added the S-waiting-on-review Status: The marked PR is awaiting review from a maintainer label Sep 17, 2025

a4lg mentioned this pull request Sep 17, 2025

RISC-V Extensions update including 29 extensions to stabilize #1987

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a4lg added 4 commits September 18, 2025 00:59

RISC-V: Remove non-existent Zb

e0393d6

The `Zb` extension does not exist and we instead have the `B` extension which is a superset of the three subextensions: `Zba`, `Zbb` and `Zbs`. For now (since `B` extension is not stabilized on Rust), this commit just removes `Zb`.

RISC-V: Fix link for zbkc

11c02f5

a4lg force-pushed the riscv-extension-ref-update-2025.1 branch from d1fcd20 to 0752505 Compare September 18, 2025 01:02

Amanieu approved these changes Sep 25, 2025

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taiki-e approved these changes Sep 26, 2025

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ehuss approved these changes Sep 29, 2025

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ehuss added this pull request to the merge queue Sep 29, 2025

ehuss removed this pull request from the merge queue due to a manual request Sep 29, 2025

Use oxford comma

1adf4c7

ehuss enabled auto-merge September 29, 2025 00:02

ehuss added this pull request to the merge queue Sep 29, 2025

Merged via the queue into rust-lang:master with commit 4c8f8b7 Sep 29, 2025
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rustbot removed the S-waiting-on-review Status: The marked PR is awaiting review from a maintainer label Sep 29, 2025

rustbot mentioned this pull request Oct 1, 2025

Update books rust-lang/rust#147236

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RISC-V: Extension Updates (including document references) #2002

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