Region inference: Simplify initialisation of region values by amandasystems · Pull Request #157672 · rust-lang/rust

amandasystems · 2026-06-09T15:41:07Z

This PR simplifies the initialisation of region values in region_infer

RegionInferenceContext::init_free_and_bound_regions() is inlined into ::new() and pulled to before initial SCC values are assigned
A couple of iteration-then-index patterns are changed into iter_enumerated()-style patterns
Some leftover code comments are removed and revised to actually describe the initialisation
Free regions are now marked as live everywhere in liveness constraints, then copied to scc_values upon initialisation, avoiding performing that logic twice
The trait used to index into SCC values goes away and the relevant methods are monomorphised and static-dispatched. This makes it easier to follow what's going on where, and possibly also shows a potential optimiser how insanely inline:able those methods are since they are used in exactly one place with exactly one type of value (though maybe it already saw that).

It should do strictly less work, but almost all of it would only happen on free regions, and there shouldn't be large numbers of those. Depending on the cleverness of the optimiser most of the option/some checks should have been compiled away anyway.

The key advantage as I see it is clearer flow: first liveness constraints are set up, then initial values are initialised, then region inference is ready to run.

rustbot · 2026-06-09T15:41:12Z

r? @davidtwco

rustbot has assigned @davidtwco.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: borrowck, compiler
borrowck, compiler expanded to 73 candidates
Random selection from 17 candidates

amandasystems · 2026-06-09T15:43:26Z

Dammit, it seems to be weirdly based on something. I'll have to rebase it.

- `RegionInferenceContext::init_free_and_bound_regions()` is inlined into `::new()` and pulled to before initial SCC values are assigned - A couple of iteration-then-index patterns are changed into `iter_enumerated()`-style patterns - Some leftover code comments are removed and revised to actually describe the initialisation - Free regions are now marked as live everywhere in liveness constraints, then copied to scc_values upon initialisation, avoiding performing that logic twice It should do strictly less work, but almost all of it would only happen on free regions, and there shouldn't be large numbers of those. Depending on the cleverness of the optimiser most of the option/some checks should have been compiled away anyway. The key advantage as I see it is clearer flow: first liveness constraints are set up, then initial values are initialised, then region inference is ready to run.

amandasystems · 2026-06-09T17:21:37Z


                    // Add all nodes in the CFG to liveness constraints
-                    self.liveness_constraints.add_all_points(variable);
-                    self.scc_values.add_all_points(scc);


Note this!

View changes since the review

davidtwco

LGTM

View changes since this review

davidtwco · 2026-06-12T16:02:11Z

@bors r+

rust-bors · 2026-06-12T16:02:15Z

📌 Commit 5c35f31 has been approved by davidtwco

It is now in the queue for this repository.

…tialisation, r=davidtwco Region inference: Simplify initialisation of region values This PR simplifies the initialisation of region values in `region_infer` - `RegionInferenceContext::init_free_and_bound_regions()` is inlined into `::new()` and pulled to before initial SCC values are assigned - A couple of iteration-then-index patterns are changed into `iter_enumerated()`-style patterns - Some leftover code comments are removed and revised to actually describe the initialisation - Free regions are now marked as live everywhere in liveness constraints, then copied to scc_values upon initialisation, avoiding performing that logic twice - The trait used to index into SCC values goes away and the relevant methods are monomorphised and static-dispatched. This makes it easier to follow what's going on where, and possibly also shows a potential optimiser how insanely inline:able those methods are since they are used in exactly one place with exactly one type of value (though maybe it already saw that). It should do strictly less work, but almost all of it would only happen on free regions, and there shouldn't be large numbers of those. Depending on the cleverness of the optimiser most of the option/some checks should have been compiled away anyway. The key advantage as I see it is clearer flow: first liveness constraints are set up, then initial values are initialised, then region inference is ready to run.

…uwer Rollup of 23 pull requests Successful merges: - #144220 (Add powerpc64-unknown-linux-gnuelfv2 target) - #153238 (debuginfo: slices are DW_TAG_array_type's) - #157112 (Update aarch64-unknown-freebsd target description) - #157322 (test pre-stabilization items on CI) - #157348 (Don't track cwd for `-Zremap-cwd-prefix` in incremental compilation) - #157490 (Add field-wise CoerceShared reborrow tests) - #157655 (Make Share::share final and improve docs) - #157672 (Region inference: Simplify initialisation of region values) - #157680 (Require `#[pin_v2]` for explicit pin-projection patterns) - #157688 (Create experimental test job `aarch64-apple-macos-26` for evaluating `macos-26` runner images) - #157796 (rustdoc: Some more lazy formatting) - #157818 (miri subtree update) - #157069 (Test that you can't implement Unpin for a compiler-generated future using TAIT) - #157079 (Don't recover `&raw EXPR` as a missing comma) - #157202 (add #[rustc_no_writable] to slice::get_unchecked_mut) - #157622 (Disable retagging for variadic arguments in const-eval) - #157684 (-Zassumptions-on-binders: insert empty assumptions when entering binders in the solver) - #157695 (Extend capabilities of `TypeFoldable_Generic`) - #157766 (interpret: avoid computing layout of sized raw pointee) - #157785 (fuchsia: Support AddressSanitizer on riscv64gc-unknown-fuchsia) - #157795 (revert 157013) - #157798 (Prevent approving PRs that wait for Crater or formal decisions) - #157803 (Rename `errors.rs` file to `diagnostics.rs` (7/N)) Failed merges: - #157752 (Rename `errors.rs` file to `diagnostics.rs` (6/N))

Rollup merge of #157672 - amandasystems:region-inference-initialisation, r=davidtwco Region inference: Simplify initialisation of region values This PR simplifies the initialisation of region values in `region_infer` - `RegionInferenceContext::init_free_and_bound_regions()` is inlined into `::new()` and pulled to before initial SCC values are assigned - A couple of iteration-then-index patterns are changed into `iter_enumerated()`-style patterns - Some leftover code comments are removed and revised to actually describe the initialisation - Free regions are now marked as live everywhere in liveness constraints, then copied to scc_values upon initialisation, avoiding performing that logic twice - The trait used to index into SCC values goes away and the relevant methods are monomorphised and static-dispatched. This makes it easier to follow what's going on where, and possibly also shows a potential optimiser how insanely inline:able those methods are since they are used in exactly one place with exactly one type of value (though maybe it already saw that). It should do strictly less work, but almost all of it would only happen on free regions, and there shouldn't be large numbers of those. Depending on the cleverness of the optimiser most of the option/some checks should have been compiled away anyway. The key advantage as I see it is clearer flow: first liveness constraints are set up, then initial values are initialised, then region inference is ready to run.

…uwer Rollup of 23 pull requests Successful merges: - rust-lang/rust#144220 (Add powerpc64-unknown-linux-gnuelfv2 target) - rust-lang/rust#153238 (debuginfo: slices are DW_TAG_array_type's) - rust-lang/rust#157112 (Update aarch64-unknown-freebsd target description) - rust-lang/rust#157322 (test pre-stabilization items on CI) - rust-lang/rust#157348 (Don't track cwd for `-Zremap-cwd-prefix` in incremental compilation) - rust-lang/rust#157490 (Add field-wise CoerceShared reborrow tests) - rust-lang/rust#157655 (Make Share::share final and improve docs) - rust-lang/rust#157672 (Region inference: Simplify initialisation of region values) - rust-lang/rust#157680 (Require `#[pin_v2]` for explicit pin-projection patterns) - rust-lang/rust#157688 (Create experimental test job `aarch64-apple-macos-26` for evaluating `macos-26` runner images) - rust-lang/rust#157796 (rustdoc: Some more lazy formatting) - rust-lang/rust#157818 (miri subtree update) - rust-lang/rust#157069 (Test that you can't implement Unpin for a compiler-generated future using TAIT) - rust-lang/rust#157079 (Don't recover `&raw EXPR` as a missing comma) - rust-lang/rust#157202 (add #[rustc_no_writable] to slice::get_unchecked_mut) - rust-lang/rust#157622 (Disable retagging for variadic arguments in const-eval) - rust-lang/rust#157684 (-Zassumptions-on-binders: insert empty assumptions when entering binders in the solver) - rust-lang/rust#157695 (Extend capabilities of `TypeFoldable_Generic`) - rust-lang/rust#157766 (interpret: avoid computing layout of sized raw pointee) - rust-lang/rust#157785 (fuchsia: Support AddressSanitizer on riscv64gc-unknown-fuchsia) - rust-lang/rust#157795 (revert 157013) - rust-lang/rust#157798 (Prevent approving PRs that wait for Crater or formal decisions) - rust-lang/rust#157803 (Rename `errors.rs` file to `diagnostics.rs` (7/N)) Failed merges: - rust-lang/rust#157752 (Rename `errors.rs` file to `diagnostics.rs` (6/N))

rustbot assigned davidtwco Jun 9, 2026

rustbot added 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 Jun 9, 2026

amandasystems marked this pull request as draft June 9, 2026 15:43

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 9, 2026

amandasystems force-pushed the region-inference-initialisation branch from ffc1eec to 9602230 Compare June 9, 2026 16:00

amandasystems force-pushed the region-inference-initialisation branch from 9602230 to 219a65f Compare June 9, 2026 16:15

amandasystems marked this pull request as ready for review June 9, 2026 16:15

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 9, 2026

amandasystems commented Jun 9, 2026

View reviewed changes

SccValues: Inline and monomorphise ToElementIndex

0b6f400

amandasystems force-pushed the region-inference-initialisation branch from 610be6c to 0b6f400 Compare June 10, 2026 13:45

Fuse the two loops and do all region initialisation in one shot

5c35f31

davidtwco approved these changes Jun 12, 2026

View reviewed changes

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 Jun 12, 2026

This was referenced Jun 12, 2026

Rollup of 23 pull requests #157827

Closed

Rollup of 23 pull requests #157828

Merged

rust-bors Bot merged commit af8cbe7 into rust-lang:main Jun 12, 2026
12 checks passed

rustbot added this to the 1.98.0 milestone Jun 12, 2026

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Region inference: Simplify initialisation of region values#157672

Region inference: Simplify initialisation of region values#157672
rust-bors[bot] merged 3 commits into
rust-lang:mainfrom
amandasystems:region-inference-initialisation

amandasystems commented Jun 9, 2026 •

edited

Loading

Uh oh!

rustbot commented Jun 9, 2026

Uh oh!

amandasystems commented Jun 9, 2026

Uh oh!

amandasystems Jun 9, 2026 •

edited by rustbot

Loading

Uh oh!

davidtwco left a comment •

edited by rustbot

Loading

Uh oh!

davidtwco commented Jun 12, 2026

Uh oh!

rust-bors Bot commented Jun 12, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Conversation

amandasystems commented Jun 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Jun 9, 2026

Uh oh!

amandasystems commented Jun 9, 2026

Uh oh!

amandasystems Jun 9, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

davidtwco left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

davidtwco commented Jun 12, 2026

Uh oh!

rust-bors Bot commented Jun 12, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

amandasystems commented Jun 9, 2026 •

edited

Loading

amandasystems Jun 9, 2026 •

edited by rustbot

Loading

davidtwco left a comment •

edited by rustbot

Loading