Annotate MIR with dataflow results for testing purposes by tmiasko · Pull Request #163721 · rust-lang/rust

tmiasko · 2026-10-03T21:32:37Z

When requested through an internal rustc attribute, include dataflow
results in MIR output, i.e., -Zunpretty=mir or --emit mir.

For now, supported dataflows are:

#[rustc_mir(rustc_pretty_live_locals)]
#[rustc_mir(rustc_pretty_transitive_live_locals)]

The mechanism is intended to supersede existing rustc_peek intrinsic.
For demonstration also migrates one of tests based on rustc_peek:
tests/ui/mir-dataflow/liveness-projection.rs.

To avoid name conflicts with dataflow directory (to be added in subsequent commit).

rustbot · 2026-10-03T21:32:41Z

Some changes occurred in compiler/rustc_attr_ir

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

rustbot · 2026-10-03T21:32:43Z

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Amanieu · 2026-10-03T23:02:32Z

Should this also use a MirDumper so that we can use EMIT_MIR annotations in the tests?

tmiasko · 2026-10-04T05:59:25Z

Is there something specific you would like to see implemented? I could try to include it in all MIR dumps, in a fixed stage, or at configurable point, ... . Alternatively, one could also teach compiletest to dump the complete MIR as opposed to merely checking it.

Amanieu · 2026-10-04T10:41:20Z

+            _ => {}
+        }
+    }
+    annotations.into_extra_data()


Suggested change

annotations.into_extra_data()

let extra_data = annotations.into_extra_data()?;

if let Some(dumper) = MirDumper::new(tcx, "DataflowPretty", body) {

dumper.set_extra_data(&*extra_data).dump_mir(body);

}

Some(extra_data)

This allows the tests to contain full snapshots of the annotated MIR with:

// EMIT_MIR liveness.fields.DataflowPretty.0.mir

View changes since the review

OK. Added with a different suffix "dataflow".

This is simpler from what I had in mind. There is a drawback that it couples -Zdump-mir and --emit mir together. That is, dumping dataflow results individually requires emitting the complete MIR.

When requested through an internal rustc attribute, include dataflow results in MIR output, i.e., `-Zunpretty=mir` or `--emit mir`. For now, supported dataflows are: * `#[rustc_mir(rustc_pretty_live_locals)]` * `#[rustc_mir(rustc_pretty_transitive_live_locals)]` The mechanism is intended to supersede existing `rustc_peek` intrinsic. For demonstration also migrates one of tests based on `rustc_peek`: tests/ui/mir-dataflow/liveness-projection.rs.

Amanieu · 2026-10-04T20:56:27Z

@bors r+

rust-bors · 2026-10-04T20:56:30Z

📌 Commit 3b3e098 has been approved by Amanieu

It is now in the queue for this repository.

rust-bors · 2026-10-05T01:36:59Z

☀️ Test successful - CI
Approved by: Amanieu
Duration: 3h 3m 57s
Pushing 260f1ac to main...

github-actions · 2026-10-05T01:40:08Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 2822155 (parent) -> 260f1ac (this PR)

Test differences

Show 16 test diffs

Stage 1

[mir-opt] tests/mir-opt/dataflow.rs: pass -> [missing] (J0)
[mir-opt] tests/mir-opt/dataflow/liveness.rs: [missing] -> pass (J0)
[mir-opt] tests/mir-opt/dump_dataflow.rs: [missing] -> pass (J0)

Stage 2

[mir-opt] tests/mir-opt/dataflow.rs: pass -> [missing] (J1)
[mir-opt] tests/mir-opt/dataflow/liveness.rs: [missing] -> pass (J1)
[mir-opt] tests/mir-opt/dump_dataflow.rs: [missing] -> pass (J1)

Additionally, 10 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 260f1acad9d7f70b5b56a636a9dc5a7f76150417 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-loongarch64-linux: 1h 16m -> 2h 8m (+68.6%)
dist-i686-mingw: 34m 28s -> 57m 10s (+65.9%)
test-x86_64-mingw-2: 1h 39m -> 2h 45m (+65.5%)
dist-ohos-armv7: 50m 5s -> 1h 16m (+52.1%)
test-pr-check-2: 28m 36s -> 42m 1s (+46.9%)
test-x86_64-gnu-next-trait-solver-polonius: 43m 10s -> 1h 2m (+44.8%)
dist-powerpc64le-linux-musl: 1h 9m -> 1h 39m (+44.1%)
test-x86_64-msvc-ext3: 1h 58m -> 1h 6m (-43.7%)
dist-x86_64-mingw: 2h 45m -> 1h 41m (-38.6%)
test-i686-gnu-2: 1h 49m -> 1h 9m (-36.6%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-10-05T02:21:29Z

Finished benchmarking commit (260f1ac): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 1.1%, secondary -1.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	0.7%	[0.7%, 0.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.2%	[-3.2%, -3.2%]	1
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

Cycles

Results (primary -2.2%, secondary 19.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	19.7%	[19.7%, 19.7%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.206s -> 490.682s (0.30%)
Artifact size: 408.62 MiB -> 408.64 MiB (0.00%)

Rename tests/mir-opt/dataflow.rs to dump_dataflow.rs

bef651b

To avoid name conflicts with dataflow directory (to be added in subsequent commit).

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 3, 2026

rustbot assigned tiif Oct 3, 2026

tmiasko mentioned this pull request Oct 3, 2026

MIR move elimination [3/6]: PreciseLiveness #163337

Merged

Amanieu reviewed Oct 4, 2026

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rust-cloud-vms Bot force-pushed the pretty-dataflow branch from 2e4f92b to 3b3e098 Compare October 4, 2026 15:13

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 4, 2026

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Oct 5, 2026

rust-bors Bot merged commit 260f1ac into rust-lang:main Oct 5, 2026
15 checks passed

rustbot added this to the 1.101.0 milestone Oct 5, 2026

tmiasko deleted the pretty-dataflow branch October 5, 2026 07:53

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Annotate MIR with dataflow results for testing purposes - #163721

Annotate MIR with dataflow results for testing purposes#163721
rust-bors[bot] merged 2 commits into
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tmiasko:pretty-dataflow

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-    annotations.into_extra_data()
+    let extra_data = annotations.into_extra_data()?;
+    if let Some(dumper) = MirDumper::new(tcx, "DataflowPretty", body) {
+        dumper.set_extra_data(&*extra_data).dump_mir(body);
+    }
+    Some(extra_data)

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Test differences

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Overall result: ❌ regressions - no action needed

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