Reinstate fast_reject for overlap checking #32748
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The initial implementation of specialization did not use the `fast_reject` mechanism when checking for overlap, which caused a serious performance regression in some cases. This commit modifies the specialization graph to use simplified types for fast rejection when possible, and along the way refactors the logic for building the specialization graph. Closes rust-lang#32499
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Note: I've confirmed locally that this resolves the coherence slowdown for winapi. |
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It'd be nice to have a regression test added to https://github.com/nrc/rustc-perf |
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@bors r+ |
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📌 Commit 9ba3d5e has been approved by |
Manishearth
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Reinstate fast_reject for overlap checking The initial implementation of specialization did not use the `fast_reject` mechanism when checking for overlap, which caused a serious performance regression in some cases. This commit modifies the specialization graph to use simplified types for fast rejection when possible, and along the way refactors the logic for building the specialization graph. Closes rust-lang#32499 r? @nikomatsakis
Manishearth
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to Manishearth/rust
that referenced
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Apr 7, 2016
Reinstate fast_reject for overlap checking The initial implementation of specialization did not use the `fast_reject` mechanism when checking for overlap, which caused a serious performance regression in some cases. This commit modifies the specialization graph to use simplified types for fast rejection when possible, and along the way refactors the logic for building the specialization graph. Closes rust-lang#32499 r? @nikomatsakis
Manishearth
added a commit
to Manishearth/rust
that referenced
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Apr 7, 2016
Reinstate fast_reject for overlap checking The initial implementation of specialization did not use the `fast_reject` mechanism when checking for overlap, which caused a serious performance regression in some cases. This commit modifies the specialization graph to use simplified types for fast rejection when possible, and along the way refactors the logic for building the specialization graph. Closes rust-lang#32499 r? @nikomatsakis
bors
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nikomatsakis
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Nominating for regression because:
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nikomatsakis
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Accepting for beta based on prior criteria. |
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I'm not sure if this backport was intended for 1.8, but it's missed that train unfortunately. Beta was branched off of b622c3e, however, which includes this commit, so I'm going to remove the beta-nominated tag as our way of indicating "backport done" is "beta-accepted" only, and the "backport" is done as this just made its way naturally into 1.9 |
alexcrichton
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The initial implementation of specialization did not use the
fast_rejectmechanism when checking for overlap, which caused aserious performance regression in some cases.
This commit modifies the specialization graph to use simplified types
for fast rejection when possible, and along the way refactors the logic
for building the specialization graph.
Closes #32499
r? @nikomatsakis