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not *all* retags might be explicit in Runtime MIR #109408

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merged 1 commit into from
Mar 21, 2023

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In #105317 I made Miri treat Rvalue::Ref/AddrOf as implicit retagging sites. This updates the MIR docs accordingly.

For Rvalue::Ref I think this makes a lot more sense: creating a new reference is their entire point, so we can avoid bloating the MIR with retags. Also this seems to be the best way to handle cases like *ptr = &[mut] ..., where doing a retag is somewhat questionable since maybe *ptr points to another place now?

For Rvalue::AddrOf, Stacked Borrows needs this because even raw ptrs need some retagging, but Tree Borrows doesn't do ant retagging here and I hope we'll end up with a model where raw pointers don't get retagged.

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rustbot commented Mar 20, 2023

r? @compiler-errors

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 20, 2023
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rustbot commented Mar 20, 2023

This PR changes MIR

cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras

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@bors r+ rollup

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bors commented Mar 20, 2023

📌 Commit 5058cc8 has been approved by compiler-errors

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 20, 2023
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 21, 2023
not *all* retags might be explicit in Runtime MIR

In rust-lang#105317 I made Miri treat `Rvalue::Ref/AddrOf` as implicit retagging sites. This updates the MIR docs accordingly.

For `Rvalue::Ref` I think this makes a lot more sense: creating a new reference is their entire point, so we can avoid bloating the MIR with retags. Also this seems to be the best way to handle cases like `*ptr = &[mut] ...`, where doing a retag is somewhat questionable since maybe `*ptr` points to another place now?

For `Rvalue::AddrOf`, Stacked Borrows needs this because even raw ptrs need some retagging, but Tree Borrows doesn't do ant retagging here and I hope we'll end up with a model where raw pointers don't get retagged.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 21, 2023
not *all* retags might be explicit in Runtime MIR

In rust-lang#105317 I made Miri treat `Rvalue::Ref/AddrOf` as implicit retagging sites. This updates the MIR docs accordingly.

For `Rvalue::Ref` I think this makes a lot more sense: creating a new reference is their entire point, so we can avoid bloating the MIR with retags. Also this seems to be the best way to handle cases like `*ptr = &[mut] ...`, where doing a retag is somewhat questionable since maybe `*ptr` points to another place now?

For `Rvalue::AddrOf`, Stacked Borrows needs this because even raw ptrs need some retagging, but Tree Borrows doesn't do ant retagging here and I hope we'll end up with a model where raw pointers don't get retagged.
Noratrieb added a commit to Noratrieb/rust that referenced this pull request Mar 21, 2023
not *all* retags might be explicit in Runtime MIR

In rust-lang#105317 I made Miri treat `Rvalue::Ref/AddrOf` as implicit retagging sites. This updates the MIR docs accordingly.

For `Rvalue::Ref` I think this makes a lot more sense: creating a new reference is their entire point, so we can avoid bloating the MIR with retags. Also this seems to be the best way to handle cases like `*ptr = &[mut] ...`, where doing a retag is somewhat questionable since maybe `*ptr` points to another place now?

For `Rvalue::AddrOf`, Stacked Borrows needs this because even raw ptrs need some retagging, but Tree Borrows doesn't do ant retagging here and I hope we'll end up with a model where raw pointers don't get retagged.
Noratrieb added a commit to Noratrieb/rust that referenced this pull request Mar 21, 2023
not *all* retags might be explicit in Runtime MIR

In rust-lang#105317 I made Miri treat `Rvalue::Ref/AddrOf` as implicit retagging sites. This updates the MIR docs accordingly.

For `Rvalue::Ref` I think this makes a lot more sense: creating a new reference is their entire point, so we can avoid bloating the MIR with retags. Also this seems to be the best way to handle cases like `*ptr = &[mut] ...`, where doing a retag is somewhat questionable since maybe `*ptr` points to another place now?

For `Rvalue::AddrOf`, Stacked Borrows needs this because even raw ptrs need some retagging, but Tree Borrows doesn't do ant retagging here and I hope we'll end up with a model where raw pointers don't get retagged.
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 21, 2023
Rollup of 10 pull requests

Successful merges:

 - rust-lang#106434 (Document `Iterator::sum/product` for Option/Result)
 - rust-lang#108326 (Implement read_buf for a few more types)
 - rust-lang#108842 (Enforce non-lifetime-binders in supertrait preds are not object safe)
 - rust-lang#108896 (new solver: make all goal evaluation able to be automatically rerun )
 - rust-lang#109124 (Add `dist.compression-profile` option to control compression speed)
 - rust-lang#109240 (Walk un-shifted nested `impl Trait` in trait when setting up default trait method assumptions)
 - rust-lang#109385 (fix typo)
 - rust-lang#109386 (add myself to mailmap)
 - rust-lang#109390 (Custom MIR: Support aggregate expressions)
 - rust-lang#109408 (not *all* retags might be explicit in Runtime MIR)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 925fbcd into rust-lang:master Mar 21, 2023
@rustbot rustbot added this to the 1.70.0 milestone Mar 21, 2023
@RalfJung RalfJung deleted the retags branch March 22, 2023 15:08
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4 participants