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Add f16 and f128 math functions #128417

Merged
merged 6 commits into from
Aug 7, 2024
Merged

Add f16 and f128 math functions #128417

merged 6 commits into from
Aug 7, 2024

Commits on Aug 1, 2024

  1. Specify the integer type of the powi LLVM intrinsic 

    Since LLVM <https://reviews.llvm.org/D99439> (4c7f820, "Update
@llvm.powi to handle different int sizes for the exponent"), the size of
the integer can be specified for the `powi` intrinsic. Make use of this
so it is more obvious that integer size is consistent across all float
types.

This feature is available since LLVM 13 (October 2021). Based on
bootstrap we currently support >= 17.0, so there should be no support
problems.
    @tgross35
    tgross35 committed Aug 1, 2024
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  2. Add math intrinsics for f16 and f128 

    These already exist in the compiler. Expose them in core so we can add
their library functions.
    @tgross35
    tgross35 committed Aug 1, 2024
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  3. Add math functions for f16 and f128 

    This adds missing functions for math operations on the new float types.

Platform support is pretty spotty at this point, since even platforms
with generally good support can be missing math functions.
`std/build.rs` is updated to reflect this.
    @tgross35
    tgross35 committed Aug 1, 2024
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  4. Add core functions for f16 and f128 that require math routines 

    `min`, `max`, and similar functions require external math routines. Add
these under the same gates as `std` math functions (`reliable_f16_math`
and `reliable_f128_math`).
    @tgross35
    tgross35 committed Aug 1, 2024
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  5. Update comments for {f16, f32, f64, f128}::midpoint 

    Clarify what makes some operations not safe, and correct comment in the
default branch ("not safe" -> "safe").
    @tgross35
    tgross35 committed Aug 1, 2024
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  6. Add a disclaimer about x86 f128 math functions 

    Due to a LLVM bug, `f128` math functions link successfully but LLVM
chooses the wrong symbols (`long double` symbols rather than those for
binary128).

Since this is a notable problem that may surprise a number of users, add
a note about it.

Link: llvm/llvm-project#44744
    @tgross35
    tgross35 committed Aug 1, 2024
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