Wrong results in some FMA cases #11
Comments
|
I've posted a PR to fix this in LLVM at llvm/llvm-project#98721. I've also made a Rust port of the fix at https://github.com/beetrees/rustc_apfloat/tree/fix-mul-add. |
|
llvm/llvm-project#63895 has been fixed upstream. Can we get that fix into the Rust port as well? :) Cc @eddyb @wesleywiser |
|
@beetrees could you make a PR for your branch? |
workingjubilee
added a commit
to workingjubilee/rustc
that referenced
this issue
Jun 12, 2025
…li-obk miri: we can use apfloat's mul_add now With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here. Fixes rust-lang/miri#2995 We already have a test for this: https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003 r? `@oli-obk`
matthiaskrgr
added a commit
to matthiaskrgr/rust
that referenced
this issue
Jun 13, 2025
…li-obk miri: we can use apfloat's mul_add now With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here. Fixes rust-lang/miri#2995 We already have a test for this: https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003 r? ``@oli-obk``
rust-timer
added a commit
to rust-lang/rust
that referenced
this issue
Jun 13, 2025
Rollup merge of #142340 - RalfJung:miri-apfloat-mul-add, r=oli-obk miri: we can use apfloat's mul_add now With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here. Fixes rust-lang/miri#2995 We already have a test for this: https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003 r? ``@oli-obk``
github-actions bot
pushed a commit
to rust-lang/miri
that referenced
this issue
Jun 14, 2025
miri: we can use apfloat's mul_add now With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here. Fixes #2995 We already have a test for this: https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003 r? ``@oli-obk``
github-actions bot
pushed a commit
to rust-lang/rustc-dev-guide
that referenced
this issue
Jun 16, 2025
miri: we can use apfloat's mul_add now With rust-lang/rustc_apfloat#11 fixed, there is no reason to still use host floats here. Fixes rust-lang/miri#2995 We already have a test for this: https://github.com/rust-lang/rust/blob/a7153db254acc387e271e75153bdbd3caa2bed89/src/tools/miri/tests/pass/float.rs#L998-L1003 r? ``@oli-obk``
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Due to this being an exact port of the LLVM library, this crate is affected by llvm/llvm-project#63895: some FMA produce wrong results. This seems worth tracking on our side as well, if only to make it easier to find, given that "produces wrong result" is the worst kind of bug.
The text was updated successfully, but these errors were encountered: