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Handle statics in MIR as const pointers #66587
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This is great, a much more principled approach than what I was attempting
@matthewjasper great work, indeed I'm working on the first 3. |
☔ The latest upstream changes (presumably #66607) made this pull request unmergeable. Please resolve the merge conflicts. |
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IMO this is ready to r+, would leave this up to @oli-obk though |
@bors r+ |
📌 Commit bccc59a has been approved by |
…t, r=oli-obk Handle statics in MIR as const pointers This is the first PR towards the goal of removing `PlaceBase::Static`. In this PR: * Statics are lowered to dereferencing a const pointer. * The temporaries holding such pointers are tracked in MIR, for the most part this is only used for diagnostics. There are two exceptions: * The borrow checker has some checks for thread-locals that directly use this data. * Const checking will suppress "cannot dereference raw pointer" diagnostics for pointers to `static mut`/`extern static`. This is to maintain the current behaviour (12 tests fail otherwise). The following are left to future PRs (I think that @spastorino will be working on the first 3): * Applying the same treatments to promoted statics. * Removing `PlaceBase::Static`. * Replacing `PlaceBase` with `Local`. * Moving the ever growing collection of metadata that we have for diagnostics in MIR passes somewhere more appropriate. r? @oli-obk
Rollup of 8 pull requests Successful merges: - #66183 (*Syntactically* permit visibilities on trait items & enum variants) - #66566 (Document pitfall with `impl PartialEq<B> for A`) - #66575 (Remove pretty printing of specific nodes in AST) - #66587 (Handle statics in MIR as const pointers) - #66619 (follow the convention in this file to use third-person singular verbs) - #66633 (Error code's long explanation cleanup) - #66637 (fix reoccuring typo: dereferencable -> dereferenceable) - #66639 (resolve: more declarative `fresh_binding`) Failed merges: r? @ghost
They now look the same in the MIR after rust-lang#66587.
Before this PR is was possible to always force a |
Do pointers track the TLS-ness of what they point to? If so, we can make const alloc codegen add those markers |
No. Only when an alloc gets directly referenced from a function, does the I have been able to solve the problem for cg_clif in bjorn3/rustc_codegen_cranelift@30de2a0. That commit makes the logic more like cg_llvm. |
So... the status is you solved the problem, but we could still improve on it by making this part of codegen_ssa to duplicate less code? |
Yes
cg_ssa already does this, but I can't use it much in cg_clif yet, as it depends to much on several llvm properties. |
This is the first PR towards the goal of removing
PlaceBase::Static
. In this PR:static mut
/extern static
. This is to maintain the current behaviour (12 tests fail otherwise).The following are left to future PRs (I think that @spastorino will be working on the first 3):
PlaceBase::Static
.PlaceBase
withLocal
.r? @oli-obk