exclude `#![no_builtins]` crates from LTO
this prevents intrinsics like `memcpy` from being mis-optimized to
infinite recursive calls when LTO is used.
fixes#31544closes#35540
---
r? @alexcrichton
cc @Amanieu
Implement the `!` type
This implements the never type (`!`) and hides it behind the feature gate `#[feature(never_type)]`. With the feature gate off, things should build as normal (although some error messages may be different). With the gate on, `!` is usable as a type and diverging type variables (ie. types that are unconstrained by anything in the code) will default to `!` instead of `()`.
Take commandline arguments into account for incr. comp.
Implements the conservative strategy described in https://github.com/rust-lang/rust/issues/33727.
From now one, every time a new commandline option is added, one has to specify if it influences the incremental compilation cache. I've tried to implement this as automatic as possible: One just has to added either the `[TRACKED]` or the `[UNTRACKED]` marker next to the field. The `Options`, `CodegenOptions`, and `DebuggingOptions` definitions in `session::config` show plenty of examples.
The PR removes some cruft from `session::config::Options`, mostly unnecessary copies of flags also present in `DebuggingOptions` or `CodeGenOptions` in the same struct.
One notable removal is the `cfg` field that contained the values passed via `--cfg` commandline arguments. I chose to remove it because (1) its content is only a subset of what later is stored in `hir::Crate::config` and it's pretty likely that reading the cfgs from `Options` would not be what you wanted, and (2) we could not incorporate it into the dep-tracking hash of the `Options` struct because of how the test framework works, leaving us with a piece of untracked but vital data.
It is now recommended (just as before) to access the crate config via the `krate()` method in the HIR map.
Because the `cfg` field is not present in the `Options` struct any more, some methods in the `CompilerCalls` trait now take the crate config as an explicit parameter -- which might constitute a breaking change for plugin authors.
The 'cfg' in the Options struct is only the commandline-specified
subset of the crate configuration and it's almost always wrong to
read that instead of the CrateConfig in HIR crate node.
Commandline arguments influence whether incremental compilation
can use its compilation cache and thus their changes relative to
previous compilation sessions need to be taking into account. This
commit makes sure that one has to specify for every commandline
argument whether it influences incremental compilation or not.
Per the discussion on #34765, we make one `DepNode::Mir` variant and use
it to represent both the MIR tracking map as well as passes that operate
on MIR. We also track loads of cached MIR (which naturally comes from
metadata).
Note that the "HAIR" pass adds a read of TypeckItemBody because it uses
a myriad of tables that are not individually tracked.
Better attribute and metaitem encapsulation throughout the compiler
This PR refactors most (hopefully all?) of the `MetaItem` interactions outside of `libsyntax` (and a few inside) to interact with MetaItems through the provided traits instead of directly creating / destruct / matching against them. This is a necessary first step to eventually converting `MetaItem`s to internally use `TokenStream` representations (which will make `MetaItem` interactions much nicer for macro writers once the new macro system is in place).
r? @nrc
We used to use `Name`, but the session outlives the tokenizer, which
means that attempts to read this field after trans has complete
otherwise panic. All reads want an `InternedString` anyhow.
