simd_reduce_min/max: remove float support

[RalfJung]

LLVM currently doesn't have an intrinsic with the right semantics here (see llvm/llvm-project#185827). The only remaining user of this intrinsic with float types is portable-simd and it's easier to implement a fallback there than here, so I opted for making the intrinsic int-only. I kept around the float support in cranelift and Miri because there it already has the desired semantics (matching scalar min/max).

Fixes #153395
Blocked on rust-lang/portable-simd#515

[rustbot]

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

Some changes occurred to the platform-builtins intrinsics. Make sure the
LLVM backend as well as portable-simd gets adapted for the changes.

cc @antoyo, @GuillaumeGomez, @bjorn3, @calebzulawski, @programmerjake

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @oli-obk, @lcnr

[rustbot]

r? @chenyukang

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[RalfJung]

I removed the GCC code because it seems completely wrong under any conceivable semantics. For an input of [0.0, NaN, 1.0, 2.0] this would return 1.0!

[GuillaumeGomez]

Thank you. T_T

[chenyukang]

This comment below still have

/// For floating-point values, uses IEEE-754 `maxNum`.`

which maybe need to be removed?

there are several similar places.

[chenyukang]

this need to change?
https://github.com/chenyukang/rust/blob/d7ab69561a799848e3f7ca6671ab6671b92475f6/library/portable-simd/crates/core_simd/src/simd/num/float.rs#L431-L441

[chenyukang]

need more reviewers from the domain
@rustbot reroll

[RalfJung]

this need to change? https://github.com/chenyukang/rust/blob/d7ab69561a799848e3f7ca6671ab6671b92475f6/library/portable-simd/crates/core_simd/src/simd/num/float.rs#L431-L441

Yeah as I said this is blocked on rust-lang/portable-simd#515.

[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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test library/core/src/unit.rs - unit::() (line 6) ... ok

failures:

---- library/core/src/../../portable-simd/crates/core_simd/src/simd/num/float.rs - core_simd::simd::num::float::SimdFloat::reduce_max (line 194) stdout ----
error[E0511]: invalid monomorphization of `simd_reduce_max` intrinsic: unsupported simd_reduce_max from `Simd<f32, 2>` with element `f32` to `f32`
   --> library/core/src/../../portable-simd/crates/core_simd/src/simd/num/float.rs:434:26
    |
434 |                 unsafe { core::intrinsics::simd::simd_reduce_max(self) }
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
447 | impl_trait! { f16 { bits: u16, mask: i16 }, f32 { bits: u32, mask: i32 }, f64 { bits: u64, mask: i64 } }
    | -------------------------------------------------------------------------------------------------------- in this macro invocation
    |
    = note: this error originates in the macro `impl_trait` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0511`.
Couldn't compile the test.
\ (no newline at end of output)
---- library/core/src/../../portable-simd/crates/core_simd/src/simd/num/float.rs - core_simd::simd::num::float::SimdFloat::reduce_max (line 194) stdout end ----
---- library/core/src/../../portable-simd/crates/core_simd/src/simd/num/float.rs - core_simd::simd::num::float::SimdFloat::reduce_min (line 221) stdout ----
error[E0511]: invalid monomorphization of `simd_reduce_min` intrinsic: unsupported simd_reduce_min from `Simd<f32, 2>` with element `f32` to `f32`
   --> library/core/src/../../portable-simd/crates/core_simd/src/simd/num/float.rs:440:26
    |
440 |                 unsafe { core::intrinsics::simd::simd_reduce_min(self) }
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
447 | impl_trait! { f16 { bits: u16, mask: i16 }, f32 { bits: u32, mask: i32 }, f64 { bits: u64, mask: i64 } }
    | -------------------------------------------------------------------------------------------------------- in this macro invocation
    |
    = note: this error originates in the macro `impl_trait` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error