LLVM 4.0 Upgrade
Since nobody has done this yet, I decided to get things started:
**Todo:**
* [x] push the relevant commits to `rust-lang/llvm` and `rust-lang/compiler-rt`
* [x] cleanup `.gitmodules`
* [x] Verify if there are any other commits from `rust-lang/llvm` which need backporting
* [x] Investigate / fix debuginfo ("`<optimized out>`") failures
* [x] Use correct emscripten version in docker image
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Closes#37609.
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**Test results:**
Everything is green 🎉
Previously the `cargotest` suite would run some arbitrary revision of Cargo's
test suite, but now that we're bundling it in tree we should be running the
Cargo submodule's test suite instead.
this commit implements the first step of the `default impl` feature:
all items in a `default impl` are (implicitly) `default` and hence
specializable.
In order to test this feature I've copied all the tests provided for the
`default` method implementation (in run-pass/specialization and
compile-fail/specialization directories) and moved the `default` keyword
from the item to the impl.
See referenced issue for further info
traits::select: quickly filter out predicates from other traits
this improves most pre-trans passes's performance by ~1%.
That missed the spring cleaning PR because I wanted to ship it.
r? @eddyb
cache dtorck constraints on ADTs
This avoids visiting the fields of all structs multiple times, improving item-bodies checking time by 10% (!).
Not sure whether we want this in 1.18 or 1.19. It's a big-ish patch, but the 10% win is very tempting.
r? @eddyb
rustc: generalize monomorphic_const_eval to polymorphic constants.
With the addition of `Substs` to the query key, we can now evaluate *and cache* polymorphic constants.
Fixes#23898 by replacing the crippled explicit-discriminant-only local-crate-only `lookup_variant_by_id` with `ConstVal::Variant` which can describe variants irrespective of their discriminant.
Fixes#41394 by fixing #23898 (for the original testcase) and by not looping past the first discriminant.
