Replace a recursive algorithm with an iterative one and a stack.#74983
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(rust_highfive has picked a reviewer for you, use r? to override) |
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@bors try @rust-timer queue Seems not unlikely to have some perf effects. |
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Awaiting bors try build completion |
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⌛ Trying commit ac5b2b0a2a6d526901b412f07651885be3c7f1f9 with merge 7ecf4177219d2b3082e0d5ee04edff8af3e1e80b... |
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☀️ Try build successful - checks-actions, checks-azure |
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Queued 7ecf4177219d2b3082e0d5ee04edff8af3e1e80b with parent 62f9aa9, future comparison URL. |
ecstatic-morse
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Thanks for doing this @oli-obk. I remember looking at this code early on and wondering if it was going to ruin someone's day 😄. This is a pretty straightforward translation of the recursive version, so I feel good about it even though I left some questions.
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Preexisting I know, but why do we only mark the MIR as changed if current != target? If current == target then we are inserting a self-loop, but it's possible for this to represent a change in the MIR if we had a cycle involving several Gotos.
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I have learned the hard way that tinkering with this code is not a good idea XD But I've also learned that you either break it completely or not at all, there's no middle ground, so I guess i can do more experimentation
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oh well, it worked :D
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If you don't wanna lump it into this PR, that's fine too. It just didn't make sense to me.
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it's already in this PR ;)
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Why the SmallVec here? In the common case, start will not refer to a Goto with no statements, so terminators will be empty.
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anecdotal evidence showed me many single-step goto chains (I had logging on during libcore builds). But we can also just go ahead and benchmark Vec vs SmallVec<[_; 1]> and maybe some other default sizes.
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I'm satisfied with that. It shouldn't matter much either way, maybe leave a comment?
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Finished benchmarking try commit (7ecf4177219d2b3082e0d5ee04edff8af3e1e80b): comparison url. Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up. @bors rollup=never |
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@bors r=ecstatic-morse |
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📌 Commit aba0251 has been approved by |
…arth Rollup of 6 pull requests Successful merges: - rust-lang#74977 (Clean up E0741 error explanation) - rust-lang#74981 (Some fixes for `plugin.md` in unstable-book) - rust-lang#74983 (Replace a recursive algorithm with an iterative one and a stack.) - rust-lang#74995 (Update the WASI libc build to LLVM 10.) - rust-lang#74996 (submodules: update cargo from 974eb438d to 2d5c2381e) - rust-lang#75007 (Clean up E0743 explanation) Failed merges: r? @ghost
fixes #74931