[experiment] eliminate dead statements while retaining debugging information

[dianqk]

I don't have a clear idea yet, but I'd like to take a look at perf first.

r? ghost

[dianqk]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 3f1d09a with merge b3ad3fca8083d45db24ea8895612040e0cedabe8...

[bors]

💔 Test failed - checks-actions

[dianqk]

@bors try @rust-timer queue

[bors]

⌛ Trying commit ed418b0 with merge bf5df2d...

[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 2.954 Building wheels for collected packages: reuse
#12 2.955   Building wheel for reuse (pyproject.toml): started
#12 3.168   Building wheel for reuse (pyproject.toml): finished with status 'done'
#12 3.169   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132719 sha256=5bb60f62728aaedff7162745ce743c7f2f55069b3e7f82e6a37d70df455797cc
#12 3.170   Stored in directory: /tmp/pip-ephem-wheel-cache-gq97jd_g/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#12 3.172 Successfully built reuse
#12 3.172 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#12 3.576 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 3.577 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 4.116 Collecting virtualenv
#12 4.154   Downloading virtualenv-20.30.0-py3-none-any.whl (4.3 MB)
#12 4.246      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 4.3/4.3 MB 48.6 MB/s eta 0:00:00
#12 4.302 Collecting platformdirs<5,>=3.9.1
#12 4.305   Downloading platformdirs-4.3.7-py3-none-any.whl (18 kB)
#12 4.323 Collecting distlib<1,>=0.3.7
#12 4.327   Downloading distlib-0.3.9-py2.py3-none-any.whl (468 kB)
#12 4.337      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 469.0/469.0 KB 55.2 MB/s eta 0:00:00
#12 4.374 Collecting filelock<4,>=3.12.2
#12 4.378   Downloading filelock-3.18.0-py3-none-any.whl (16 kB)
#12 4.459 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.643 Successfully installed distlib-0.3.9 filelock-3.18.0 platformdirs-4.3.7 virtualenv-20.30.0
#12 4.643 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 4.7s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
DirectMap4k:      118720 kB
DirectMap2M:     4075520 kB
DirectMap1G:    14680064 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 } -- 0.216
---
fmt check
fmt: checked 5981 files
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs:208: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
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: Tue Apr 22 00:39:37 UTC 2025
  network time: Tue, 22 Apr 2025 00:39:37 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[bors]

☀️ Try build successful - checks-actions
Build commit: bf5df2d (bf5df2d521771a0774baccb586bfe531e205d258)

[rust-timer]

Finished benchmarking commit (bf5df2d): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	2.9%	[0.2%, 12.3%]	18
Regressions ❌ (secondary)	0.3%	[0.1%, 1.2%]	16
Improvements ✅ (primary)	-0.5%	[-1.3%, -0.2%]	12
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.2%]	15
All ❌✅ (primary)	1.5%	[-1.3%, 12.3%]	30

Max RSS (memory usage)

Results (primary -0.8%, secondary 2.9%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.4%, 3.2%]	7
Regressions ❌ (secondary)	2.9%	[2.9%, 2.9%]	1
Improvements ✅ (primary)	-1.9%	[-6.3%, -0.4%]	14
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.8%	[-6.3%, 3.2%]	21

Cycles

Results (primary 2.8%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	6.9%	[0.5%, 13.4%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-1.4%, -0.4%]	8
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[-1.4%, 13.4%]	15

Binary size

Results (primary 0.1%, secondary -0.1%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.0%, 4.6%]	44
Regressions ❌ (secondary)	0.2%	[0.1%, 0.3%]	13
Improvements ✅ (primary)	-0.3%	[-8.5%, -0.0%]	43
Improvements ✅ (secondary)	-0.2%	[-0.7%, -0.0%]	58
All ❌✅ (primary)	0.1%	[-8.5%, 4.6%]	87

Bootstrap: 774.01s -> 773.408s (-0.08%)
Artifact size: 365.04 MiB -> 365.06 MiB (0.01%)