Implement the internal feature `cfg_target_has_reliable_f16_f128` #140323

tgross35 · 2025-04-26T05:09:41Z

Support for f16 and f128 is varied across targets, backends, and backend versions. Eventually we would like to reach a point where all backends support these approximately equally, but until then we have to work around some of these nuances of support being observable.

Introduce the cfg_target_has_reliable_f16_f128 internal feature, which provides the following new configuration gates:

cfg(target_has_reliable_f16)
cfg(target_has_reliable_f16_math)
cfg(target_has_reliable_f128)
cfg(target_has_reliable_f128_math)

reliable_f16 and reliable_f128 indicate that basic arithmetic for the type works correctly. The _math versions indicate that anything relying on libm works correctly, since sometimes this hits a separate class of codegen bugs.

These options match configuration set by the build script at 1. The logic for LLVM support is duplicated as-is from the same script. There are a few possible updates that will come as a follow up.

The config introduced here is not planned to ever become stable, it is only intended to replace the build scripts for std tests and compiler-builtins that don't have any way to configure based on the codegen backend.

MCP: rust-lang/compiler-team#866
Closes: rust-lang/compiler-team#866

The second commit makes use of this config to replace cfg_{f16,f128}{,_math} in library/. I omitted providing a cfg(bootstrap) configuration to keep things simpler since the next beta branch is in two weeks.

try-job: aarch64-gnu
try-job: i686-msvc-1
try-job: test-various
try-job: x86_64-gnu
try-job: x86_64-msvc-ext2

r? @ghost

tgross35 · 2025-04-26T06:21:28Z

@bors try

Implement the internal feature `cfg_target_has_reliable_f16_f128` Support for `f16` and `f128` is varied across targets, backends, and backend versions. Eventually we would like to reach a point where all backends support these approximately equally, but until then we have to work around some of these nuances of support being observable. Introduce the `target_has_reliable_f16_f128` configuration option, gated behind `cfg_target_has_reliable_f16_f128`, as an indicator for whether or not the backend supports these types to a point that they can and should be tested. The configuration mostly follows the logic used by `target_feature`, and similarly takes a value: #[cfg(target_has_reliable_f16_f128 = "f16")] Accepted values are: * `f16` * `f16-math` * `f128` * `f128-math` `f16` and `f128` indicate that basic arithmetic for the type works correctly. The `-math` versions indicate that anything relying on `libm` works correctly, since sometimes this hits a separate class of codegen bugs. These options match configuration set by the build script at [1]. The logic for LLVM support is duplicated as-is from the same script. There are a few possible updates that will come as a follow up. The config introduced here is not intended to ever become stable, it is only intended to replace the build scripts for `std` tests and in `compiler-builtins` that don't have any way to set configuration based on the codegen backend. MCP: rust-lang/compiler-team#866 Closes: rust-lang/compiler-team#866 [1]: https://github.com/rust-lang/rust/blob/555e1d0386f024a8359645c3217f4b3eae9be042/library/std/build.rs#L84-L186 --- The second commit makes use of this config to replace `cfg_{f16,f128}{,_math}` in `library/`. try-job: aarch64-gnu try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2

bors · 2025-04-26T06:22:39Z

⌛ Trying commit e7fb9c5 with merge 4055b73...

rustbot · 2025-04-26T06:42:48Z

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in cfg and check-cfg configuration

cc @Urgau

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

tgross35 · 2025-04-26T06:43:52Z

r? compiler

Cc @bjorn3 @antoyo since this touches the backend interfaces.

compiler/rustc_session/src/config/cfg.rs

rustbot · 2025-04-26T07:16:54Z

Some changes occurred in src/doc/rustc/src/check-cfg.md

cc @Urgau

tgross35 · 2025-04-26T07:30:51Z

Hm... I think I'm actually leaning toward four separate key-only cfg options here rather than a single key with multiple values. I don't think the current version works as-well, it's a bit bulky and redundant with f16_f128 in the name.

Will change it over tomorrow unless anyone has a stronger preference.

@rustbot author

rustbot · 2025-04-26T07:30:55Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

tgross35 · 2025-04-26T20:26:42Z

Changed so this is split across four different cfg options.

@rustbot review

compiler/rustc_session/src/config/cfg.rs

src/doc/rustc/src/check-cfg.md

tests/ui/float/target-has-reliable-nightly-float.rs

compiler/rustc_session/src/config/cfg.rs

tgross35 · 2025-04-27T17:44:06Z

Since you have already started taking a look,

r? @Urgau

Implement the internal feature `cfg_target_has_reliable_f16_f128` Support for `f16` and `f128` is varied across targets, backends, and backend versions. Eventually we would like to reach a point where all backends support these approximately equally, but until then we have to work around some of these nuances of support being observable. Introduce the `cfg_target_has_reliable_f16_f128` internal feature, which provides the following new configuration gates: * `cfg(target_has_reliable_f16)` * `cfg(target_has_reliable_f16_math)` * `cfg(target_has_reliable_f128)` * `cfg(target_has_reliable_f128_math)` `reliable_f16` and `reliable_f128` indicate that basic arithmetic for the type works correctly. The `_math` versions indicate that anything relying on `libm` works correctly, since sometimes this hits a separate class of codegen bugs. These options match configuration set by the build script at [1]. The logic for LLVM support is duplicated as-is from the same script. There are a few possible updates that will come as a follow up. The config introduced here is not planned to ever become stable, it is only intended to replace the build scripts for `std` tests and `compiler-builtins` that don't have any way to configure based on the codegen backend. MCP: rust-lang/compiler-team#866 Closes: rust-lang/compiler-team#866 [1]: https://github.com/rust-lang/rust/blob/555e1d0386f024a8359645c3217f4b3eae9be042/library/std/build.rs#L84-L186 --- The second commit makes use of this config to replace `cfg_{f16,f128}{,_math}` in `library/`. I omitted providing a `cfg(bootstrap)` configuration to keep things simpler since the next beta branch is in two weeks. try-job: aarch64-gnu try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2

…enton Rollup of 10 pull requests Successful merges: - rust-lang#139308 (add autodiff inline) - rust-lang#139656 (Stabilize `slice_as_chunks` library feature) - rust-lang#140022 (allow deref patterns to move out of boxes) - rust-lang#140276 (Do not compute type_of for impl item if impl where clauses are unsatisfied) - rust-lang#140302 (Move inline asm check to typeck, properly handle aliases) - rust-lang#140323 (Implement the internal feature `cfg_target_has_reliable_f16_f128`) - rust-lang#140391 (Rename sub_ptr to offset_from_unsigned in docs) - rust-lang#140394 (Make bootstrap git tests more self-contained) - rust-lang#140396 (Workaround for windows-gnu rust-lld test failure) - rust-lang#140402 (only return nested goals for `Certainty::Yes`) Failed merges: - rust-lang#139765 ([beta] Delay `hash_extract_if` stabilization from 1.87 to 1.88) r? `@ghost` `@rustbot` modify labels: rollup

…enton Rollup of 10 pull requests Successful merges: - rust-lang#139308 (add autodiff inline) - rust-lang#139656 (Stabilize `slice_as_chunks` library feature) - rust-lang#140022 (allow deref patterns to move out of boxes) - rust-lang#140276 (Do not compute type_of for impl item if impl where clauses are unsatisfied) - rust-lang#140302 (Move inline asm check to typeck, properly handle aliases) - rust-lang#140323 (Implement the internal feature `cfg_target_has_reliable_f16_f128`) - rust-lang#140391 (Rename sub_ptr to offset_from_unsigned in docs) - rust-lang#140394 (Make bootstrap git tests more self-contained) - rust-lang#140396 (Workaround for windows-gnu rust-lld test failure) - rust-lang#140402 (only return nested goals for `Certainty::Yes`) r? `@ghost` `@rustbot` modify labels: rollup

[experiment] reliable float experiments Trying a few blocked things based on top of rust-lang#140323. r? `@ghost` try-job: aarch64-gnu try-job: i686-gnu-1 try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2

[experiment] reliable float experiments Trying a few blocked things based on top of rust-lang#140323. r? `@ghost` try-job: x86_64-gnu-llvm-19-1 try-job: x86_64-gnu-llvm-20-1

[experiment] reliable float experiments Trying a few blocked things based on top of rust-lang#140323. r? `@ghost` try-job: aarch64-gnu try-job: i686-gnu-1 try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2 try-job: x86_64-gnu-llvm-19-1 try-job: x86_64-gnu-llvm-20-1

Rollup merge of rust-lang#140323 - tgross35:cfg-unstable-float, r=Urgau Implement the internal feature `cfg_target_has_reliable_f16_f128` Support for `f16` and `f128` is varied across targets, backends, and backend versions. Eventually we would like to reach a point where all backends support these approximately equally, but until then we have to work around some of these nuances of support being observable. Introduce the `cfg_target_has_reliable_f16_f128` internal feature, which provides the following new configuration gates: * `cfg(target_has_reliable_f16)` * `cfg(target_has_reliable_f16_math)` * `cfg(target_has_reliable_f128)` * `cfg(target_has_reliable_f128_math)` `reliable_f16` and `reliable_f128` indicate that basic arithmetic for the type works correctly. The `_math` versions indicate that anything relying on `libm` works correctly, since sometimes this hits a separate class of codegen bugs. These options match configuration set by the build script at [1]. The logic for LLVM support is duplicated as-is from the same script. There are a few possible updates that will come as a follow up. The config introduced here is not planned to ever become stable, it is only intended to replace the build scripts for `std` tests and `compiler-builtins` that don't have any way to configure based on the codegen backend. MCP: rust-lang/compiler-team#866 Closes: rust-lang/compiler-team#866 [1]: https://github.com/rust-lang/rust/blob/555e1d0386f024a8359645c3217f4b3eae9be042/library/std/build.rs#L84-L186 --- The second commit makes use of this config to replace `cfg_{f16,f128}{,_math}` in `library/`. I omitted providing a `cfg(bootstrap)` configuration to keep things simpler since the next beta branch is in two weeks. try-job: aarch64-gnu try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2

This was missed as part of [1]. [1]: rust-lang#140323

…, r=jieyouxu Update documentation for `fn target_config` This was missed as part of [1]. [1]: rust-lang#140323

Rollup merge of rust-lang#140432 - tgross35:target-config-docs-update, r=jieyouxu Update documentation for `fn target_config` This was missed as part of [1]. [1]: rust-lang#140323

Implement the internal feature `cfg_target_has_reliable_f16_f128` Support for `f16` and `f128` is varied across targets, backends, and backend versions. Eventually we would like to reach a point where all backends support these approximately equally, but until then we have to work around some of these nuances of support being observable. Introduce the `cfg_target_has_reliable_f16_f128` internal feature, which provides the following new configuration gates: * `cfg(target_has_reliable_f16)` * `cfg(target_has_reliable_f16_math)` * `cfg(target_has_reliable_f128)` * `cfg(target_has_reliable_f128_math)` `reliable_f16` and `reliable_f128` indicate that basic arithmetic for the type works correctly. The `_math` versions indicate that anything relying on `libm` works correctly, since sometimes this hits a separate class of codegen bugs. These options match configuration set by the build script at [1]. The logic for LLVM support is duplicated as-is from the same script. There are a few possible updates that will come as a follow up. The config introduced here is not planned to ever become stable, it is only intended to replace the build scripts for `std` tests and `compiler-builtins` that don't have any way to configure based on the codegen backend. MCP: rust-lang/compiler-team#866 Closes: rust-lang/compiler-team#866 [1]: https://github.com/rust-lang/rust/blob/555e1d0386f024a8359645c3217f4b3eae9be042/library/std/build.rs#L84-L186 --- The second commit makes use of this config to replace `cfg_{f16,f128}{,_math}` in `library/`. I omitted providing a `cfg(bootstrap)` configuration to keep things simpler since the next beta branch is in two weeks. try-job: aarch64-gnu try-job: i686-msvc-1 try-job: test-various try-job: x86_64-gnu try-job: x86_64-msvc-ext2

…illaumeGomez Allow `#![doc(test(attr(..)))]` everywhere This PR adds the ability to specify [`#![doc(test(attr(..)))]`](https://doc.rust-lang.org/nightly/rustdoc/write-documentation/the-doc-attribute.html#testattr) ~~at module level~~ everywhere in addition to allowing it at crate-root. This is motivated by a recent PR rust-lang#140323 (by `@tgross35)` where we have to duplicate 2 attributes to every single `f16` and `f128` doctests, by allowing `#![doc(test(attr(..)))]` at module level (and everywhere else) we can omit them entirely and just have (in both module): ```rust #![doc(test(attr(feature(cfg_target_has_reliable_f16_f128))))] #![doc(test(attr(expect(internal_features))))] ``` Those new attributes are appended to the one found at crate-root or at a previous module. Those "global" attributes are compatible with merged doctests (they already were before). Given the small addition that this is, I'm proposing to insta-stabilize it, but I can feature-gate it if preferred. Best reviewed commit by commit. r? `@GuillaumeGomez`

…illaumeGomez Allow `#![doc(test(attr(..)))]` everywhere This PR adds the ability to specify [`#![doc(test(attr(..)))]`](https://doc.rust-lang.org/nightly/rustdoc/write-documentation/the-doc-attribute.html#testattr) ~~at module level~~ everywhere in addition to allowing it at crate-root. This is motivated by a recent PR rust-lang#140323 (by ``@tgross35)`` where we have to duplicate 2 attributes to every single `f16` and `f128` doctests, by allowing `#![doc(test(attr(..)))]` at module level (and everywhere else) we can omit them entirely and just have (in both module): ```rust #![doc(test(attr(feature(cfg_target_has_reliable_f16_f128))))] #![doc(test(attr(expect(internal_features))))] ``` Those new attributes are appended to the one found at crate-root or at a previous module. Those "global" attributes are compatible with merged doctests (they already were before). Given the small addition that this is, I'm proposing to insta-stabilize it, but I can feature-gate it if preferred. Best reviewed commit by commit. r? ``@GuillaumeGomez``

…illaumeGomez Allow `#![doc(test(attr(..)))]` everywhere This PR adds the ability to specify [`#![doc(test(attr(..)))]`](https://doc.rust-lang.org/nightly/rustdoc/write-documentation/the-doc-attribute.html#testattr) ~~at module level~~ everywhere in addition to allowing it at crate-root. This is motivated by a recent PR rust-lang#140323 (by ```@tgross35)``` where we have to duplicate 2 attributes to every single `f16` and `f128` doctests, by allowing `#![doc(test(attr(..)))]` at module level (and everywhere else) we can omit them entirely and just have (in both module): ```rust #![doc(test(attr(feature(cfg_target_has_reliable_f16_f128))))] #![doc(test(attr(expect(internal_features))))] ``` Those new attributes are appended to the one found at crate-root or at a previous module. Those "global" attributes are compatible with merged doctests (they already were before). Given the small addition that this is, I'm proposing to insta-stabilize it, but I can feature-gate it if preferred. Best reviewed commit by commit. r? ```@GuillaumeGomez```

…illaumeGomez Allow `#![doc(test(attr(..)))]` everywhere This PR adds the ability to specify [`#![doc(test(attr(..)))]`](https://doc.rust-lang.org/nightly/rustdoc/write-documentation/the-doc-attribute.html#testattr) ~~at module level~~ everywhere in addition to allowing it at crate-root. This is motivated by a recent PR rust-lang#140323 (by ````@tgross35)```` where we have to duplicate 2 attributes to every single `f16` and `f128` doctests, by allowing `#![doc(test(attr(..)))]` at module level (and everywhere else) we can omit them entirely and just have (in both module): ```rust #![doc(test(attr(feature(cfg_target_has_reliable_f16_f128))))] #![doc(test(attr(expect(internal_features))))] ``` Those new attributes are appended to the one found at crate-root or at a previous module. Those "global" attributes are compatible with merged doctests (they already were before). Given the small addition that this is, I'm proposing to insta-stabilize it, but I can feature-gate it if preferred. Best reviewed commit by commit. r? ````@GuillaumeGomez````

Rollup merge of #140560 - Urgau:test_attr-module-level, r=GuillaumeGomez Allow `#![doc(test(attr(..)))]` everywhere This PR adds the ability to specify [`#![doc(test(attr(..)))]`](https://doc.rust-lang.org/nightly/rustdoc/write-documentation/the-doc-attribute.html#testattr) ~~at module level~~ everywhere in addition to allowing it at crate-root. This is motivated by a recent PR #140323 (by ````@tgross35)```` where we have to duplicate 2 attributes to every single `f16` and `f128` doctests, by allowing `#![doc(test(attr(..)))]` at module level (and everywhere else) we can omit them entirely and just have (in both module): ```rust #![doc(test(attr(feature(cfg_target_has_reliable_f16_f128))))] #![doc(test(attr(expect(internal_features))))] ``` Those new attributes are appended to the one found at crate-root or at a previous module. Those "global" attributes are compatible with merged doctests (they already were before). Given the small addition that this is, I'm proposing to insta-stabilize it, but I can feature-gate it if preferred. Best reviewed commit by commit. r? ````@GuillaumeGomez````

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 26, 2025

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tgross35 added the F-f16_and_f128 `#![feature(f16)]`, `#![feature(f128)]` label Apr 26, 2025

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tgross35 mentioned this pull request Apr 28, 2025

Tracking Issue for f16 and f128 float types #116909

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ChrisDenton mentioned this pull request Apr 28, 2025

Rollup of 10 pull requests #140414

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Rollup of 10 pull requests #140415

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tgross35 mentioned this pull request Apr 29, 2025

[experiment] reliable float experiments #140424

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bors merged commit e082bf3 into rust-lang:master Apr 29, 2025
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Update documentation for fn target_config

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This was missed as part of [1]. [1]: rust-lang#140323

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Update documentation for fn target_config #140432

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Rollup merge of rust-lang#140432 - tgross35:target-config-docs-update…

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…, r=jieyouxu Update documentation for `fn target_config` This was missed as part of [1]. [1]: rust-lang#140323

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libm 0.2.12 breaks rust-gpu Rust-GPU/rust-gpu#242

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Rollup merge of rust-lang#140432 - tgross35:target-config-docs-update…

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…, r=jieyouxu Update documentation for `fn target_config` This was missed as part of [1]. [1]: rust-lang#140323

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Initial implementation of core_float_math #138087

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Allow #![doc(test(attr(..)))] everywhere #140560

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