constify float::{div,rem}_euclid#141755
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Add const support for the float rounding methods floor, ceil, trunc,
fract, round and round_ties_even.
This works by moving the calculation logic from
src/tools/miri/src/intrinsics/mod.rs
into
compiler/rustc_const_eval/src/interpret/intrinsics.rs.
All relevant method definitions were adjusted to include the `const`
keyword for all supported float types: f16, f32, f64 and f128.
The constness is hidden behind the feature gate
feature(const_float_round_methods)
which is tracked in
rust-lang#141555
This commit is a squash of the following commits:
- test: add tests that we expect to pass when float rounding becomes const
- feat: make float rounding methods `const`
- fix: replace `rustc_allow_const_fn_unstable(core_intrinsics)` attribute with `#[rustc_const_unstable(feature = "f128", issue = "116909")]` in `library/core/src/num/f128.rs`
- revert: undo update to `library/stdarch`
- refactor: replace multiple `float_<mode>_intrinsic` rounding methods with a single, parametrized one
- fix: add `#[cfg(not(bootstrap))]` to new const method tests
- test: add extra sign tests to check `+0.0` and `-0.0`
- revert: undo accidental changes to `round` docs
- fix: gate `const` float round method behind `const_float_round_methods`
- fix: remove unnecessary `#![feature(const_float_methods)]`
- fix: remove unnecessary `#![feature(const_float_methods)]` [2]
- revert: undo changes to `tests/ui/consts/const-eval/float_methods.rs`
- fix: adjust after rebase
- test: fix float tests
- test: add tests for `fract`
- chore: add commented-out `const_float_round_methods` feature gates to `f16` and `f128`
- fix: adjust NaN when rounding floats
- chore: add FIXME comment for de-duplicating float tests
- test: remove unnecessary test file `tests/ui/consts/const-eval/float_methods.rs`
- test: fix tests after upstream simplification of how float tests are run
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Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr The Miri subtree was changed cc @rust-lang/miri Some changes occurred to the CTFE / Miri interpreter cc @rust-lang/miri Some changes occurred to the CTFE machinery |
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Unfortunately I'm not sure if we should do this yet; these methods don't do correct rounding and I think we want to fix that first, which #134145 proposes to do. It would be difficult to keep I take it you have a use for these? :) |
No, I was just bothered by the fact that one of the tests in this big macro in |
That sounds like they would become intrinsics and we could have them in const -- but that would require a softfloat implementation in const-eval. |
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If it's eventually in libm I think we would likely be able to use the generic implementations to do that. I just did a bit of a scratch test using apfloat in our generic sqrt which seems to work, modulo some probably-fixable rounding bugs in f64 and f128 rust-lang/compiler-builtins@54ef3d9. (Not that sqrt itself is all that useful given Miri has an implementation). |
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Well I guess we shouldn't constify it yet then, and the issue with the tests is already tracked in #141726. |
4 participants
Tracking issue: #141572
Based on top of #141521; only the last two commits are new.
r? @tgross35