Make a subset of libm symbols weakly available on all platforms
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018616e ("Always have math functions but with `weak` linking attribute if we can") made all math symbols available on platforms that support weak linkage. This caused some unexpected regressions, however, because our less accurate and sometimes slow routines were being selected over the system `libm`, which also tends to be weak [1]. Thus, 0fab77e ("Don't include `math` for `unix` and `wasi` targets") was applied to undo these changes on many platforms. Now that some improvements have been made to `libm`, add back a subset of these functions: * cbrt * ceil * copysign * fabs * fdim * floor * fma * fmax * fmaximum * fmin * fminimum * fmod * rint * round * roundeven * sqrt * trunc This list includes only functions that produce exact results (verified with exhaustive / extensive tests, and also required by IEEE in most cases), and for which benchmarks indicate performance similar to or better than Musl's soft float math routines [^1]. All except `cbrt` also have `f16` and `f128` implementations. Once more routines meet these criteria, we can move them from platform-specific availability to always available. Once this change makes it to rust-lang/rust, we will also be able to move the relevant functions from `std` to `core`. [^1]: We still rely on the backend to provide optimized assmebly routines when available. [1]: rust-lang/rust#128386
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Since [1], `compiler-builtins` makes a certain set of math symbols weakly available on all platforms. This means we can begin exposing some of the related functions in `core`, so begin this process here. It is not possible to provide inerent methods in both `core` and `std` while giving them different stability gates, so standalone functions are added instead. This provides a way to experiment with the functionality while unstable; once it is time to stabilize, they can be converted to inherent. For `f16` and `f128`, everything is unstable so we can move the inherent methods. [1]: rust-lang/compiler-builtins#763
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Includes a change to make a subset of math symbols available on all platforms [1]. [1]: rust-lang/compiler-builtins#763
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1]. [1]: rust-lang/compiler-builtins#763 try-job: aarch64-gnu try-job: armhf-gnu try-job: i686-gnu-1 try-job: i686-mingw-1 try-job: i686-mingw-2 try-job: test-various try-job: x86_64-msvc-1 try-job: x86_64-msvc-2
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1]. [1]: rust-lang/compiler-builtins#763 try-job: aarch64-gnu try-job: armhf-gnu try-job: i686-gnu-1 try-job: i686-mingw-1 try-job: i686-mingw-2 try-job: test-various try-job: x86_64-msvc-1 try-job: x86_64-msvc-2
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Includes a change to make a subset of math symbols available on all platforms [1]. [1]: rust-lang/compiler-builtins#763
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1]. [1]: rust-lang/compiler-builtins#763 try-job: dist-various-1 try-job: dist-various-2 try-job: dist-aarch64-linux try-job: dist-x86_64-linux
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Includes a change to make a subset of math symbols available on all platforms [1], and disables `f16` on aarch64 without neon [2]. [1]: rust-lang/compiler-builtins#763 [2]: rust-lang/compiler-builtins#775
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1], and disables `f16` on aarch64 without neon [2]. [1]: rust-lang/compiler-builtins#763 [2]: rust-lang/compiler-builtins#775 try-job: aarch64-gnu try-job: aarch64-gnu-debug try-job: armhf-gnu try-job: dist-various-1 try-job: dist-various-2 try-job: dist-aarch64-linux try-job: dist-arm-linux try-job: dist-armv7-linux try-job: dist-x86_64-linux try-job: test-various
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1], and disables `f16` on aarch64 without neon [2]. [1]: rust-lang/compiler-builtins#763 [2]: rust-lang/compiler-builtins#775 try-job: aarch64-gnu try-job: aarch64-gnu-debug try-job: armhf-gnu try-job: dist-various-1 try-job: dist-various-2 try-job: dist-aarch64-linux try-job: dist-arm-linux try-job: dist-armv7-linux try-job: dist-x86_64-linux try-job: test-various
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Update `compiler-builtins` to 0.1.149 Includes a change to make a subset of math symbols available on all platforms [1], and disables `f16` on aarch64 without neon [2]. [1]: rust-lang/compiler-builtins#763 [2]: rust-lang/compiler-builtins#775 try-job: aarch64-gnu try-job: aarch64-gnu-debug try-job: armhf-gnu try-job: dist-various-1 try-job: dist-various-2 try-job: dist-aarch64-linux try-job: dist-arm-linux try-job: dist-armv7-linux try-job: dist-x86_64-linux try-job: test-various
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018616e ("Always have math functions but with
weaklinking attribute if we can") made all math symbols available on platforms that support weak linkage. This caused some unexpected regressions, however, because our less accurate and sometimes slow routines were being selected over the systemlibm, which also tends to be weak 1. Thus, 0fab77e ("Don't includemathforunixandwasitargets") was applied to undo these changes on many platforms.Now that some improvements have been made to
libm, add back a subset of these functions:This list includes only functions that produce exact results (verified with exhaustive / extensive tests, and also required by IEEE in most cases), and for which benchmarks indicate performance similar to or better than Musl's soft float math routines 1. All except
cbrtalso havef16andf128implementations. Once more routines meet these criteria, we can move them from platform-specific availability to always available.Once this change makes it to rust-lang/rust, we will also be able to move the relevant functions from
stdtocore.Footnotes
We still rely on the backend to provide optimized assmebly
routines when available. ↩