Allow reifying intrinsics to fn pointers. (rebase of #86699)

[GrigorenkoPV]

The original PR (#86699) died after merge conflicts due to inactivity.

Might allow to re-revert #81238.

I was able to do a rebase (mostly), but, sadly, I am underqualified to deal with the remaining issues. So, E-help-wanted label.

Current problems:

• There is an ICE because of broken MIR (see e8ef4ef). Maybe this can be used to aid solving the issue?
• The additions to tests/mir-opt/lower_intrinsics.rs do not actually get tested (this is even reported by tidy). The directives are missing. In the original PR they were in the middle of the function and without any indentation: src. I could not get this to work with the current testing infrastructure. Also see these review comments.

[rustbot]

r? @pnkfelix

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[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[compiler-errors]

I'll review this soon

[compiler-errors]

Why was this added?

[compiler-errors]

Actually, I know why. I wonder if it's better to place this in build_call_shim, or even make our own function like build_reified_intrinsic.

[compiler-errors]

Generally looks fine.

I think this needs a T-types FCP since AFAICT the only way to hit this is on nightly code. Is that last part correct?

Regardless, do you mind writing up a short blurb motivating why we want to do this and explaining the general approach?

[compiler-errors]

First this needs a rebase and also please fix the CI issues

@rustbot author

[GrigorenkoPV]

First this needs a rebase

Done

and also please fix the CI issues

Sorry, I've tried, but couldn't figure out what the problem was and why it didn't pick up the mir test. I would appreciate if somebody could help me here.

[GrigorenkoPV]

@rustbot label +E-help-wanted

[bors]

☔ The latest upstream changes (presumably #127831) made this pull request unmergeable. Please resolve the merge conflicts.

[jieyouxu]

Maybe

// EMIT_MIR lower_intrinsics.reify_intrinsics.LowerIntrinsics.mir

?

[GrigorenkoPV]

Well, I think this should be a .diff to preserve the original intentions. Plus I was not able to make it generate the same code as in #86699.

[GrigorenkoPV]

I've rebased and found a place where this ICEs. I am not sure whether the ICE was there originally or it got introduced after one of the rebases.

[GrigorenkoPV]

I've rebased and found a place where this ICEs. I am not sure whether the ICE was there originally or it got introduced after one of the rebases.

I've checked and this ICE has been present since the first version of this PR. I was not able to check whether it existed in the original #86699, because I couldn't get that old version of the compiler to build.

[Dylan-DPC]

@GrigorenkoPV any updates on this? thanks

[rust-log-analyzer]

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

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

info: removing rustup binaries
info: rustup is uninstalled
##[group]Image checksum input
mingw-check-tidy
# We use the ghcr base image because ghcr doesn't have a rate limit
# and the mingw-check-tidy job doesn't cache docker images in CI.
FROM ghcr.io/rust-lang/ubuntu:22.04
ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y --no-install-recommends \
  g++ \
  make \
---

COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/

# NOTE: intentionally uses python2 for x.py so we can test it still works.
# validate-toolstate only runs in our CI, so it's ok for it to only support python3.
ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
           --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
# This file is autogenerated by pip-compile with Python 3.10
# by the following command:
#
#    pip-compile --allow-unsafe --generate-hashes reuse-requirements.in
---
#12 2.798 Building wheels for collected packages: reuse
#12 2.800   Building wheel for reuse (pyproject.toml): started
#12 3.007   Building wheel for reuse (pyproject.toml): finished with status 'done'
#12 3.008   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132719 sha256=be6760d5849de4a58bbe52b85ca57a55f2b32b518b17029a5ad2e530db0d4303
#12 3.008   Stored in directory: /tmp/pip-ephem-wheel-cache-2ssrxpj7/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#12 3.011 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#12 3.400 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#12 3.401 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
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#12 3.957   Downloading virtualenv-20.29.1-py3-none-any.whl (4.3 MB)
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#12 4.264 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.442 Successfully installed distlib-0.3.9 filelock-3.17.0 platformdirs-4.3.6 virtualenv-20.29.1
#12 DONE 4.5s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
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##[endgroup]
Executing TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
    Finished `dev` profile [unoptimized] target(s) in 0.05s
##[endgroup]
WARN: currently no CI rustc builds have rustc debug assertions enabled. Please either set `rust.debug-assertions` to `false` if you want to use download CI rustc or set `rust.download-rustc` to `false`.
downloading https://static.rust-lang.org/dist/2025-02-08/rustfmt-nightly-x86_64-unknown-linux-gnu.tar.xz
---
##[endgroup]
fmt check
fmt: checked 5835 files
tidy check
tidy error: the following output file is not associated with any mir-opt test, you can remove it: /checkout/tests/mir-opt/lower_intrinsics.core.intrinsics-#1-forget.LowerIntrinsics.diff
tidy error: the following output file is not associated with any mir-opt test, you can remove it: /checkout/tests/mir-opt/lower_intrinsics.core.intrinsics-#1-size_of.LowerIntrinsics.diff
tidy error: the following output file is not associated with any mir-opt test, you can remove it: /checkout/tests/mir-opt/lower_intrinsics.core.intrinsics-#1-discriminant_value.LowerIntrinsics.diff
tidy error: the following output file is not associated with any mir-opt test, you can remove it: /checkout/tests/mir-opt/lower_intrinsics.core.intrinsics-#1-unreachable.LowerIntrinsics.diff
tidy error: the following output file is not associated with any mir-opt test, you can remove it: /checkout/tests/mir-opt/lower_intrinsics.core.intrinsics-#1-wrapping_add.LowerIntrinsics.diff
removing old virtual environment
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (24.3.1)
  Downloading pip-25.0.1-py3-none-any.whl.metadata (3.7 kB)
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Installing collected packages: pip
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All checks passed!
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some tidy checks failed
Command has failed. Rerun with -v to see more details.
  local time: Sun Feb  9 23:35:10 UTC 2025
  network time: Sun, 09 Feb 2025 23:35:11 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[GrigorenkoPV]

@GrigorenkoPV any updates on this? thanks

I've rebased to resolve the merge conflicts. As for the remaining issues (outlined them in the OP), I am underqualified to resolve those on my own. I would either need some help with this, or someone to take over the PR entirely. Alternatively, I could try to just brute-force my way through, gaining the qualification in process, but that would take more time than I can currently dedicate to this, sadly.