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fuchsia / third_party / rust / 3f9aa50b70e8833656d557aa963e339faca0a4c6
commit3f9aa50b70e8833656d557aa963e339faca0a4c6[log] [tgz]
authorTrevor Gross <t.gross35@gmail.com>Fri Oct 11 23:57:44 2024 -0400
committerGitHub <noreply@github.com>Fri Oct 11 23:57:44 2024 -0400
treebb838846810b68bd96127303c82deb61c40fa8ae
parentfb20e4d3b96d1de459d086980a8b99d5060ad9fe [diff]
parent0d8a978e8a55b08778ec6ee861c2c5ed6703eb6c [diff]
Rollup merge of #124874 - jedbrown:float-mul-add-fast, r=saethlin

intrinsics fmuladdf{32,64}: expose llvm.fmuladd.* semantics

Add intrinsics `fmuladd{f32,f64}`. This computes `(a * b) + c`, to be fused if the code generator determines that (i) the target instruction set has support for a fused operation, and (ii) that the fused operation is more efficient than the equivalent, separate pair of `mul` and `add` instructions.

https://llvm.org/docs/LangRef.html#llvm-fmuladd-intrinsic

The codegen_cranelift uses the `fma` function from libc, which is a correct implementation, but without the desired performance semantic. I think this requires an update to cranelift to expose a suitable instruction in its IR.

I have not tested with codegen_gcc, but it should behave the same way (using `fma` from libc).

---
This topic has been discussed a few times on Zulip and was suggested, for example, by `@workingjubilee` in [Effect of fma disabled](https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/Effect.20of.20fma.20disabled/near/274179331).
tree: bb838846810b68bd96127303c82deb61c40fa8ae
  1. .github/
  2. compiler/
  3. library/
  4. LICENSES/
  5. src/
  6. tests/
  7. .clang-format
  8. .editorconfig
  9. .git-blame-ignore-revs
  10. .gitattributes
  11. .gitignore
  12. .gitmodules
  13. .ignore
  14. .mailmap
  15. Cargo.lock
  16. Cargo.toml
  17. CODE_OF_CONDUCT.md
  18. config.example.toml
  19. configure
  20. CONTRIBUTING.md
  21. COPYRIGHT
  22. INSTALL.md
  23. LICENSE-APACHE
  24. LICENSE-MIT
  25. README.md
  26. RELEASES.md
  27. REUSE.toml
  28. rust-bors.toml
  29. rustfmt.toml
  30. triagebot.toml
  31. x
  32. x.ps1
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README.md

Website | Getting started | Learn | Documentation | Contributing

This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.

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