Implement explicit tail calls in the LLVM backend

[semtexzv]

Implements guaranteed tail calls in the LLVM backend (#112788):

[rustbot]

r? @Mark-Simulacrum

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[rustbot]

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

This PR modifies run-make tests.

cc @jieyouxu

[oxalica]

With this, I think we can enable drop-order test now: https://github.com/rust-lang/rust/blob/989d72f9abc1b4f43b2233ba0664736dc30c69e3/tests/ui/explicit-tail-calls/drop-order.rs

[semtexzv]

Looking at the recent comments to understand the GCC backend implementation issue

[rustbot]

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

[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 2.727 Building wheels for collected packages: reuse
#12 2.728   Building wheel for reuse (pyproject.toml): started
#12 2.936   Building wheel for reuse (pyproject.toml): finished with status 'done'
#12 2.937   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132720 sha256=0c2fd2aaf7b0bf8d6e131220aff14712a774c2ca462f3204d25460cbcf610b63
#12 2.937   Stored in directory: /tmp/pip-ephem-wheel-cache-qmtrwz7r/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#12 2.940 Successfully built reuse
#12 2.940 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#12 3.334 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 3.335 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
#12 3.860 Collecting virtualenv
#12 3.896   Downloading virtualenv-20.29.3-py3-none-any.whl (4.3 MB)
#12 3.960      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 4.3/4.3 MB 70.1 MB/s eta 0:00:00
#12 4.018 Collecting filelock<4,>=3.12.2
#12 4.021   Downloading filelock-3.18.0-py3-none-any.whl (16 kB)
#12 4.038 Collecting distlib<1,>=0.3.7
#12 4.041   Downloading distlib-0.3.9-py2.py3-none-any.whl (468 kB)
#12 4.048      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 469.0/469.0 KB 86.3 MB/s eta 0:00:00
#12 4.080 Collecting platformdirs<5,>=3.9.1
#12 4.083   Downloading platformdirs-4.3.6-py3-none-any.whl (18 kB)
#12 4.164 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.345 Successfully installed distlib-0.3.9 filelock-3.18.0 platformdirs-4.3.6 virtualenv-20.29.3
#12 4.345 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
#12 DONE 4.4s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
DirectMap4k:      128960 kB
DirectMap2M:     6162432 kB
DirectMap1G:    12582912 kB
##[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
##[group]Building bootstrap
    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`.
[TIMING] core::build_steps::tool::LibcxxVersionTool { target: x86_64-unknown-linux-gnu } -- 0.212
---
fmt check
fmt: checked 5908 files
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/mutual-recursion.rs:48: trailing whitespace
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/mutual-recursion.rs:50: line longer than 100 chars
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/mutual-recursion.rs:56: trailing whitespace
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/mutual-recursion.rs:58: trailing whitespace
tidy error: /checkout/tests/ui/explicit-tail-calls/mutual-recursion.rs: missing trailing newline
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/runtime-deep-recursion.rs:23: trailing whitespace
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/runtime-deep-recursion.rs:28: trailing whitespace
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/runtime-deep-recursion.rs:34: trailing whitespace
tidy error: /checkout/tests/ui/explicit-tail-calls/runtime-deep-recursion.rs: missing trailing newline
##[error]tidy error: /checkout/tests/ui/explicit-tail-calls/llvm-ir-tail-call.rs:28: trailing whitespace
tidy error: /checkout/tests/ui/explicit-tail-calls/llvm-ir-tail-call.rs: missing trailing newline
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 (25.0.1)
linting python files
All checks passed!
checking python file formatting
26 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:44
  local time: Sun Mar 16 11:48:17 UTC 2025
  network time: Sun, 16 Mar 2025 11:48:17 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[workingjubilee]

This is not how we do codegen tests.

[workingjubilee]

https://rustc-dev-guide.rust-lang.org/tests/compiletest.html#codegen-tests

[workingjubilee]

In addition, we have entirely removed support for Makefile-based tests. This test tests nothing, that's why it passes.

[WaffleLapkin]

r? WaffleLapkin

[WaffleLapkin]

@semtexzv thanks for your PR!

Do you plan to work on this further?

As @workingjubilee said ~3 weeks ago, the test you've added doesn't actually test anything. The CI is currently failing. I also have a lot of thoughts on the implementation details. All in all there is still quite a bit of work to be done before this can be merged.

Do you have the capacity and desire to continue? I'm a bit concerned that this might be too much for a first time contributor (feel free to prove me wrong tho!)

@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.