encounter each module. This is somewhat different than how it used to
work; it should ensure a more equitable distribution of work than
before. The reason is that, before, when we rotated, we would rotate
before we had seen the full contents of the current module. So e.g. if
we have `mod a { mod b { .. } .. }`, then we rotate when we encounter
`b`, but we haven't processed the remainder of `a` yet. Unclear if this
makes any difference in practice, but it seemed suboptimal. Also, this
structure (with an outer walk over modules) is closer to what we will
want for an incremental setting.
noteworthy because trans got mildly simpler, since it doesn't have to
ensure that we walk the contents of all things just to find all the
hidden items.
Introduce a `SwitchInt` and restructure pattern matching to collect integers and characters into one master switch. This is aimed at #29227, but is not a complete fix. Whereas before we generated an if-else-if chain and, at least on my machine, just failed to compile, we now spend ~9sec compiling `rustc_abuse`. AFAICT this is basically just due to a need for more micro-optimization of the matching process: perf shows a fair amount of time just spent iterating over the candidate list. Still, it seemed worth opening a PR with this step alone, since it's a big step forward.
Function arguments that are small aggregates get passed as integer types
instead. To correctly handle that, we need to use store_ty instead of
plain Store.
Note: for now, this change only affects `-windows-gnu` builds.
So why was this `libgcc` dylib dependency needed in the first place?
The stack unwinder needs to know about locations of unwind tables of all the modules loaded in the current process. The easiest portable way of achieving this is to have each module register itself with the unwinder when loaded into the process. All modules compiled by GCC do this by calling the __register_frame_info() in their startup code (that's `crtbegin.o` and `crtend.o`, which are automatically linked into any gcc output).
Another important piece is that there should be only one copy of the unwinder (and thus unwind tables registry) in the process. This pretty much means that the unwinder must be in a shared library (unless everything is statically linked).
Now, Rust compiler tries very hard to make sure that any given Rust crate appears in the final output just once. So if we link the unwinder statically to one of Rust's crates, everything should be fine.
Unfortunately, GCC startup objects are built under assumption that `libgcc` is the one true place for the unwind info registry, so I couldn't find any better way than to replace them. So out go `crtbegin`/`crtend`, in come `rsbegin`/`rsend`!
A side benefit of this change is that rustc is now more in control of the command line that goes to the linker, so we could stop using `gcc` as the linker driver and just invoke `ld` directly.
Motivation:
- It is not actually a pattern
- It is not actually needed, except for...
Drawback:
- Slice patterns like `[a, _.., b]` are pretty-printed as `[a, .., b]`. Great loss :(
plugin-[breaking-change], as always
Similarly to the simd intrinsics. I believe this is a better solution than #29288, and I could implement it as well for overflowing_add/sub/mul. Also rename from udiv/sdiv to div, and same for rem.
when evaluating a recursive type, the `type_of` of the interior could be
still in progress, so trying to get its size would cause an ICE.
Fixes#19001
r? @eddyb
