rustc_apfloat: Double::mul_add_r panic with specific values

[mjdr]

Code related to issue #93224

[rust-highfive]

Changes rustc_apfloat. rustc_apfloat is currently in limbo and you almost certainly don't want to change it (see #55993).

cc @eddyb

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @wesleywiser (or someone else) soon.

Please see the contribution instructions for more information.

[rust-log-analyzer]

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

running 50 tests
..............................F...................
failures:

---- issue_93224 stdout ----
thread 'issue_93224' panicked at 'assertion failed: `(left == right)`
 right: `0`', compiler/rustc_apfloat/src/ieee.rs:2545:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace



failures:
    issue_93224

test result: FAILED. 49 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

error: test failed, to rerun pass '-p rustc_apfloat --test ieee'


command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "16" "--release" "--locked" "--color" "always" "--features" " llvm" "--manifest-path" "/checkout/compiler/rustc/Cargo.toml" "-p" "rustc_apfloat" "--" "--quiet"


Build completed unsuccessfully in 0:23:44

[wesleywiser]

Nominating for discussion at the compiler team meeting because I'm not sure what to do with apfloat changes in light of #55993.

[apiraino]

This is waiting on #96784 (if i am not mistaken)

[eddyb]

I posted a longer update to #55993 (comment) regarding the progress with the whole rustc_apfloat situation, but of note for this PR is that the WIP repo already has this bug fixed.

[wesleywiser]

Hey @mjdr, thanks for your PR! As @eddyb noted, this has been fixed by the new version of rustc_apfloat that #113843 switched us to using.

Thanks again for your efforts! 🙂