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Auto merge of #111673 - cjgillot:dominator-preprocess, r=cjgillot,tmiasko

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Preprocess and cache dominator tree

Preprocessing dominators has a very strong effect for https://github.com/rust-lang/rust/pull/111344.
That pass checks that assignments dominate their uses repeatedly. Using the unprocessed dominator tree caused a quadratic runtime (number of bbs x depth of the dominator tree).

This PR also caches the dominator tree and the pre-processed dominators in the MIR cfg cache.

Rebase of https://github.com/rust-lang/rust/pull/107157
cc `@tmiasko`
This commit is contained in:
bors 2023-05-24 16:18:21 +00:00
commit 97d328012b
9 changed files with 107 additions and 51 deletions
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5
compiler/rustc_middle/src/mir/basic_blocks.rs
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@ -27,6 +27,7 @@ struct Cache {
switch_sources: OnceCell<SwitchSources>,
is_cyclic: OnceCell<bool>,
postorder: OnceCell<Vec<BasicBlock>>,
dominators: OnceCell<Dominators<BasicBlock>>,
}
impl<'tcx> BasicBlocks<'tcx> {
@ -41,8 +42,8 @@ impl<'tcx> BasicBlocks<'tcx> {
*self.cache.is_cyclic.get_or_init(|| graph::is_cyclic(self))
}
pub fn dominators(&self) -> Dominators<BasicBlock> {
dominators(&self)
pub fn dominators(&self) -> &Dominators<BasicBlock> {
self.cache.dominators.get_or_init(|| dominators(self))
}
/// Returns predecessors for each basic block.