Auto merge of #110569 - saethlin:mir-pass-cooperation, r=cjgillot

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Deduplicate unreachable blocks, for real this time

In https://github.com/rust-lang/rust/pull/106428 (in particular 41eda69516) we noticed that inlining `unreachable_unchecked` can produce duplicate unreachable blocks. So we improved two MIR optimizations: `SimplifyCfg` was given a simplify to deduplicate unreachable blocks, then `InstCombine` was given a combiner to deduplicate switch targets that point at the same block. The problem is that change doesn't actually work.

Our current pass order is
```
SimplifyCfg (does nothing relevant to this situation)
Inline (produces multiple unreachable blocks)
InstCombine (doesn't do anything here, oops)
SimplifyCfg (produces the duplicate SwitchTargets that InstCombine is looking for)
```

So in here, I have factored out the specific function from `InstCombine` and placed it inside the simplify that produces the case it is looking for. This should ensure that it runs in the scenario it was designed for.

Fixes https://github.com/rust-lang/rust/issues/110551
r? `@cjgillot`

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bors 2023-04-21 15:08:02 +00:00

parent f0605fa8d0 c353ea0e93

commit 8a76857c06

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