rust/compiler/rustc_mir
bors 704e47f78b Auto merge of #78407 - oli-obk:ub_checkable_ctfe, r=RalfJung,pnkfelix
Make CTFE able to check for UB...

... by not doing any optimizations on the `const fn` MIR used in CTFE. This means we duplicate all `const fn`'s MIR now, once for CTFE, once for runtime. This PR is for checking the perf effect, so we have some data when talking about https://github.com/rust-lang/const-eval/blob/master/rfcs/0000-const-ub.md

To do this, we now have two queries for obtaining mir: `optimized_mir` and `mir_for_ctfe`. It is now illegal to invoke `optimized_mir` to obtain the MIR of a const/static item's initializer, an array length, an inline const expression or an enum discriminant initializer. For `const fn`, both `optimized_mir` and `mir_for_ctfe` work, the former returning the MIR that LLVM should use if the function is called at runtime. Similarly it is illegal to invoke `mir_for_ctfe` on regular functions.

This is all checked via appropriate assertions and I don't think it is easy to get wrong, as there should be no `mir_for_ctfe` calls outside the const evaluator or metadata encoding. Almost all rustc devs should keep using `optimized_mir` (or `instance_mir` for that matter).
2021-01-12 17:26:56 +00:00
..
src Auto merge of #78407 - oli-obk:ub_checkable_ctfe, r=RalfJung,pnkfelix 2021-01-12 17:26:56 +00:00
Cargo.toml Auto merge of #78399 - vn-ki:gsgdt-graphviz, r=oli-obk 2020-12-15 22:00:02 +00:00