coverage: Prefer to visit nodes whose predecessors have been visited #133946
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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☔ The latest upstream changes (presumably #133089) made this pull request unmergeable. Please resolve the merge conflicts. |
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The new traversal is also easier to grok @bors r+ |
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coverage: Prefer to visit nodes whose predecessors have been visited In coverage instrumentation, we need to traverse the control-flow graph and decide what kind of counter (physical counter or counter-expression) should be used for each node that needs a counter. The existing traversal order is complex and hard to tweak. This new traversal order tries to be a bit more principled, by always preferring to visit nodes whose predecessors have already been visited, which is a good match for how the counter-creation code ends up dealing with a node's in-edges and out-edges. For several of the coverage tests, this ends up being a strict improvement in reducing the size of the coverage metadata, and also reducing the number of physical counters needed. (The new traversal should hopefully also allow some further code simplifications in the future.) --- This is made possible by the separate simplification pass introduced by rust-lang#133849. Without that, almost any change to the traversal order ends up increasing the size of the expression table or the number of physical counters.
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coverage: Prefer to visit nodes whose predecessors have been visited In coverage instrumentation, we need to traverse the control-flow graph and decide what kind of counter (physical counter or counter-expression) should be used for each node that needs a counter. The existing traversal order is complex and hard to tweak. This new traversal order tries to be a bit more principled, by always preferring to visit nodes whose predecessors have already been visited, which is a good match for how the counter-creation code ends up dealing with a node's in-edges and out-edges. For several of the coverage tests, this ends up being a strict improvement in reducing the size of the coverage metadata, and also reducing the number of physical counters needed. (The new traversal should hopefully also allow some further code simplifications in the future.) --- This is made possible by the separate simplification pass introduced by rust-lang#133849. Without that, almost any change to the traversal order ends up increasing the size of the expression table or the number of physical counters.
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Rollup of 10 pull requests Successful merges: - rust-lang#131558 (Lint on combining `#[no_mangle]` and `#[export_name]`) - rust-lang#133122 (Add unpolished, experimental support for AFIDT (async fn in dyn trait)) - rust-lang#133184 (wasi/fs: Improve stopping condition for <ReadDir as Iterator>::next) - rust-lang#133456 (Add licenses + Run `cargo update`) - rust-lang#133472 (Run TLS destructors for wasm32-wasip1-threads) - rust-lang#133853 (use vendor sources by default on dist tarballs) - rust-lang#133946 (coverage: Prefer to visit nodes whose predecessors have been visited) - rust-lang#134010 (fix ICE on type error in promoted) - rust-lang#134029 (coverage: Use a query to find counters/expressions that must be zero) - rust-lang#134071 (Configure renovatebot) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 10 pull requests Successful merges: - rust-lang#131558 (Lint on combining `#[no_mangle]` and `#[export_name]`) - rust-lang#133184 (wasi/fs: Improve stopping condition for <ReadDir as Iterator>::next) - rust-lang#133456 (Add licenses + Run `cargo update`) - rust-lang#133472 (Run TLS destructors for wasm32-wasip1-threads) - rust-lang#133853 (use vendor sources by default on dist tarballs) - rust-lang#133946 (coverage: Prefer to visit nodes whose predecessors have been visited) - rust-lang#134010 (fix ICE on type error in promoted) - rust-lang#134029 (coverage: Use a query to find counters/expressions that must be zero) - rust-lang#134071 (Configure renovatebot) - rust-lang#134102 (Miscellaneous fixes for nix-dev-shell) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#133946 - Zalathar:ready-first, r=oli-obk coverage: Prefer to visit nodes whose predecessors have been visited In coverage instrumentation, we need to traverse the control-flow graph and decide what kind of counter (physical counter or counter-expression) should be used for each node that needs a counter. The existing traversal order is complex and hard to tweak. This new traversal order tries to be a bit more principled, by always preferring to visit nodes whose predecessors have already been visited, which is a good match for how the counter-creation code ends up dealing with a node's in-edges and out-edges. For several of the coverage tests, this ends up being a strict improvement in reducing the size of the coverage metadata, and also reducing the number of physical counters needed. (The new traversal should hopefully also allow some further code simplifications in the future.) --- This is made possible by the separate simplification pass introduced by rust-lang#133849. Without that, almost any change to the traversal order ends up increasing the size of the expression table or the number of physical counters.
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In coverage instrumentation, we need to traverse the control-flow graph and decide what kind of counter (physical counter or counter-expression) should be used for each node that needs a counter.
The existing traversal order is complex and hard to tweak. This new traversal order tries to be a bit more principled, by always preferring to visit nodes whose predecessors have already been visited, which is a good match for how the counter-creation code ends up dealing with a node's in-edges and out-edges.
For several of the coverage tests, this ends up being a strict improvement in reducing the size of the coverage metadata, and also reducing the number of physical counters needed.
(The new traversal should hopefully also allow some further code simplifications in the future.)
This is made possible by the separate simplification pass introduced by #133849. Without that, almost any change to the traversal order ends up increasing the size of the expression table or the number of physical counters.