Test suite assumes that cos, exp, and other functions have deterministic precision #463
Description
After landing rust-lang/rust#138062, the portable-simd test suite no longer passes in Miri:
0.005650 ---- f32::cos::lanes_1 stdout ---- 0.000026 0.000010 thread 'f32::cos::lanes_1' panicked at /home/runner/work/miri-test-libstd/miri-test-libstd/rust-src-patched/library/portable-simd/crates/test_helpers/src/lib.rs:126:43: 0.000008 called `Result::unwrap()` on an `Err` value: Fail(Reason("assertion failed: `(left == right)` \n left: `[-0.7418637 (bf3deac8)]`,\n right: `[-0.7418636 (bf3deac6)]` at crates/test_helpers/src/lib.rs:183"), [-207806100.0]) 0.000008 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace 0.000007 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect 0.000007 0.000007 ---- f32::cos::lanes_2 stdout ---- 0.000007 0.000007 thread 'f32::cos::lanes_2' panicked at /home/runner/work/miri-test-libstd/miri-test-libstd/rust-src-patched/library/portable-simd/crates/test_helpers/src/lib.rs:126:43: 0.000007 called `Result::unwrap()` on an `Err` value: Fail(Reason("assertion failed: `(left == right)` \n left: `[-0.7418637 (bf3deac8), 1.0 (3f800000)]`,\n right: `[-0.74186367 (bf3deac7), 1.0 (3f800000)]` at crates/test_helpers/src/lib.rs:183"), [-207806100.0, 0.0]) 0.000022 failures: 0.070860 f32::cos::lanes_1 0.014170 f32::cos::lanes_2 0.013913 f32::cos::lanes_3 0.015623 f32::cos::lanes_6 0.013689 f32::exp2::lanes_1 0.014103 f32::exp2::lanes_2 0.015393 f32::exp2::lanes_3 0.013566 f32::exp2::lanes_6 0.013604 f32::exp::lanes_1 0.015736 f32::exp::lanes_2 0.013619 f32::exp::lanes_3 0.013681 f32::exp::lanes_6 0.013655 f32::ln::lanes_1 0.015216 f32::ln::lanes_2 0.013688 f32::ln::lanes_3 0.013658 f32::ln::lanes_6 0.015251 f32::log10::lanes_1 0.013628 f32::log10::lanes_2 0.013611 f32::log10::lanes_3 0.015248 f32::log10::lanes_6 0.013703 f32::log2::lanes_1 0.013625 f32::log2::lanes_2 0.015322 f32::log2::lanes_3 0.014007 f32::log2::lanes_6 0.013735 f32::log::lanes_2 0.015216 f32::log::lanes_3 0.013565 f32::log::lanes_6 0.013636 f32::sin::lanes_1 0.015283 f32::sin::lanes_2 0.014103 f32::sin::lanes_3 0.013599 f32::sin::lanes_6 0.015191 f64::cos::lanes_1 0.013988 f64::cos::lanes_2 0.013582 f64::cos::lanes_3 0.013634 f64::cos::lanes_6 0.015589 f64::exp2::lanes_1 0.013691 f64::exp2::lanes_2 0.013704 f64::exp2::lanes_3 0.015679 f64::exp2::lanes_6 0.013647 f64::exp::lanes_1 0.014061 f64::exp::lanes_2 0.015406 f64::exp::lanes_3 0.013673 f64::exp::lanes_6 0.013610 f64::ln::lanes_1 0.015338 f64::ln::lanes_2 0.013550 f64::ln::lanes_3 0.013579 f64::ln::lanes_6 0.015199 f64::log10::lanes_1 0.013582 f64::log10::lanes_2 0.013587 f64::log10::lanes_3 0.015058 f64::log10::lanes_6 0.013520 f64::log2::lanes_1 0.013474 f64::log2::lanes_2 0.013490 f64::log2::lanes_3 0.014898 f64::log2::lanes_6 0.013661 f64::log::lanes_1 0.013527 f64::log::lanes_2 0.014919 f64::log::lanes_3 0.013641 f64::log::lanes_6 0.013585 f64::sin::lanes_1 0.015452 f64::sin::lanes_2 0.013729 f64::sin::lanes_3 0.013687 f64::sin::lanes_6 These functions do not have guaranteed precision, so results should probably by compared with assert_approx_ex instead of assert_eq, at least when running in Miri.