Simplifications in match lowering #126835

Nadrieril · 2024-06-22T16:21:37Z

A series of small simplifications and deduplications in the MIR lowering of patterns.

This commit was obtained by repeatedly inlining and simplifying.

Nadrieril · 2024-06-22T16:26:12Z

compiler/rustc_mir_build/src/build/matches/mod.rs

-            let mut next = Some(&candidate);
-            while let Some(candidate_ref) = next.take() {
-                for binding in &candidate_ref.extra_data.bindings {
+            // `try_to_place` may fail if it is unable to resolve the given `PlaceBuilder` inside a
+            // closure. In this case, we don't want to include a scrutinee place.
+            // `scrutinee_place_builder` will fail for destructured assignments. This is because a
+            // closure only captures the precise places that it will read and as a result a closure
+            // may not capture the entire tuple/struct and rather have individual places that will
+            // be read in the final MIR.
+            // Example:
+            // ```
+            // let foo = (0, 1);
+            // let c = || {
+            //    let (v1, v2) = foo;
+            // };
+            // ```
+            if let Some(place) = initializer.try_to_place(self) {
+                visit_bindings(&[&mut candidate], |binding: &Binding<'_>| {
                    let local = self.var_local_id(binding.var_id, OutsideGuard);
-                    // `try_to_place` may fail if it is unable to resolve the given
-                    // `PlaceBuilder` inside a closure. In this case, we don't want to include
-                    // a scrutinee place. `scrutinee_place_builder` will fail for destructured
-                    // assignments. This is because a closure only captures the precise places
-                    // that it will read and as a result a closure may not capture the entire
-                    // tuple/struct and rather have individual places that will be read in the
-                    // final MIR.
-                    // Example:
-                    // ```
-                    // let foo = (0, 1);
-                    // let c = || {
-                    //    let (v1, v2) = foo;
-                    // };
-                    // ```
-                    if let Some(place) = initializer.try_to_place(self) {
-                        let LocalInfo::User(BindingForm::Var(VarBindingForm {
-                            opt_match_place: Some((ref mut match_place, _)),
-                            ..
-                        })) = **self.local_decls[local].local_info.as_mut().assert_crate_local()
-                        else {
-                            bug!("Let binding to non-user variable.")
-                        };
+                    if let LocalInfo::User(BindingForm::Var(VarBindingForm {
+                        opt_match_place: Some((ref mut match_place, _)),
+                        ..
+                    })) = **self.local_decls[local].local_info.as_mut().assert_crate_local()
+                    {
                        *match_place = Some(place);
-                    }
-                }
-                // All of the subcandidates should bind the same locals, so we
-                // only visit the first one.
-                next = candidate_ref.subcandidates.get(0)
+                    } else {
+                        bug!("Let binding to non-user variable.")
+                    };
+                });


I guess this isn't so much a simplification by itself; it's just making my life simpler as I try to clarify this whole thing.

This commit too was obtained by repeatedly inlining and simplifying.

Zalathar · 2024-06-26T01:34:16Z

compiler/rustc_mir_build/src/build/block.rs

+                                    false,
+                                    true,


This sort of thing makes me want to start adding dedicated enums to replace some of these magic booleans.

For example, I want to replace declare_let_bindings: bool with a three-way enum:

enum DeclareLetBindings { Yes, No, LetNotPermitted, }

I've opened a draft PR to replace some booleans with enums: #126981.

matthewjasper · 2024-06-27T14:04:16Z

I think it makes sense to merge this separately from #126981.

@bors r+

bors · 2024-06-27T14:04:19Z

📌 Commit beb1d35 has been approved by matthewjasper

It is now in the queue for this repository.

…atthewjasper Simplifications in match lowering A series of small simplifications and deduplications in the MIR lowering of patterns. r? `@matthewjasper`

…llaumeGomez Rollup of 10 pull requests Successful merges: - rust-lang#123237 (Various rustc_codegen_ssa cleanups) - rust-lang#123714 (Add test for fn pointer duplication.) - rust-lang#124091 (Update AST validation module docs) - rust-lang#126835 (Simplifications in match lowering) - rust-lang#126963 (Add basic Serde serialization capabilities to Stable MIR) - rust-lang#127010 (Update browser-ui-test version to `0.18.0`) - rust-lang#127015 (Switch back `non_local_definitions` lint to allow-by-default) - rust-lang#127016 (docs: check if the disambiguator matches its suffix) - rust-lang#127029 (Fix Markdown tables in platform-support.md) - rust-lang#127032 (Enable const casting for `f16` and `f128`) r? `@ghost` `@rustbot` modify labels: rollup

…atthewjasper Simplifications in match lowering A series of small simplifications and deduplications in the MIR lowering of patterns. r? ``@matthewjasper``

…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#123237 (Various rustc_codegen_ssa cleanups) - rust-lang#123714 (Add test for fn pointer duplication.) - rust-lang#124091 (Update AST validation module docs) - rust-lang#126835 (Simplifications in match lowering) - rust-lang#126963 (Add basic Serde serialization capabilities to Stable MIR) - rust-lang#127010 (Update browser-ui-test version to `0.18.0`) - rust-lang#127015 (Switch back `non_local_definitions` lint to allow-by-default) - rust-lang#127029 (Fix Markdown tables in platform-support.md) - rust-lang#127032 (Enable const casting for `f16` and `f128`) r? `@ghost` `@rustbot` modify labels: rollup

…atthewjasper Simplifications in match lowering A series of small simplifications and deduplications in the MIR lowering of patterns. r? ```@matthewjasper```

…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#123237 (Various rustc_codegen_ssa cleanups) - rust-lang#123714 (Add test for fn pointer duplication.) - rust-lang#124091 (Update AST validation module docs) - rust-lang#126835 (Simplifications in match lowering) - rust-lang#126963 (Add basic Serde serialization capabilities to Stable MIR) - rust-lang#127015 (Switch back `non_local_definitions` lint to allow-by-default) - rust-lang#127029 (Fix Markdown tables in platform-support.md) - rust-lang#127032 (Enable const casting for `f16` and `f128`) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#126822 (Bootstrap command refactoring: port more `Command` usages to `BootstrapCmd` (step 2)) - rust-lang#126835 (Simplifications in match lowering) - rust-lang#126953 (std: separate TLS key creation from TLS access) - rust-lang#127045 (Rename `super_predicates_of` and similar queries to `explicit_*` to note that they're not elaborated) - rust-lang#127075 (rustc_data_structures: Explicitly check for 64-bit atomics support) - rust-lang#127101 (remove redundant match statement from dataflow const prop) - rust-lang#127102 (Rename fuchsia builder and bump Fuchsia) - rust-lang#127103 (Move binder and polarity parsing into `parse_generic_ty_bound`) - rust-lang#127108 (unify `dylib` and `bin_helpers` and create `shared_helpers::parse_value_from_args`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#126835 - Nadrieril:reify-decision-tree, r=matthewjasper Simplifications in match lowering A series of small simplifications and deduplications in the MIR lowering of patterns. r? ````@matthewjasper````

Nadrieril added 5 commits June 19, 2024 23:31

We can traverse bindings before lower_match_tree now

ea29d6a

Only one caller of lower_match_tree was using the fake borrows

012626b

Small dedup

cef49f7

There's nothing to bind for a wildcard

878ccd2

This commit was obtained by repeatedly inlining and simplifying.

Move lower_match_tree

c0c6c32

rustbot assigned matthewjasper Jun 22, 2024

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 22, 2024

Nadrieril commented Jun 22, 2024

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Nadrieril added 3 commits June 22, 2024 19:05

Don't use fake wildcards when we can get the failure block directly

7b150a1

This commit too was obtained by repeatedly inlining and simplifying.

Reuse lower_let_expr for let .. else lowering

ff49c37

Change comment to reflect switch to THIR unsafeck

beb1d35

Nadrieril force-pushed the reify-decision-tree branch from b408228 to beb1d35 Compare June 22, 2024 17:06

Zalathar reviewed Jun 26, 2024

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Zalathar mentioned this pull request Jun 26, 2024

Replace some magic booleans in match-lowering with enums #126981

Merged

bors 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 27, 2024

GuillaumeGomez mentioned this pull request Jun 27, 2024

Rollup of 10 pull requests #127046

Closed

matthiaskrgr mentioned this pull request Jun 27, 2024

Rollup of 9 pull requests #127056

Closed

matthiaskrgr mentioned this pull request Jun 28, 2024

Rollup of 8 pull requests #127066

Closed

matthiaskrgr mentioned this pull request Jun 29, 2024

Rollup of 9 pull requests #127111

Merged

bors merged commit 806c5c1 into rust-lang:master Jun 29, 2024
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rustbot added this to the 1.81.0 milestone Jun 29, 2024

Nadrieril deleted the reify-decision-tree branch June 29, 2024 12:34

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Simplifications in match lowering #126835

Simplifications in match lowering #126835

Nadrieril commented Jun 22, 2024

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Zalathar Jun 26, 2024 •

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matthewjasper commented Jun 27, 2024

bors commented Jun 27, 2024

Simplifications in match lowering #126835

Simplifications in match lowering #126835

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