brson/rust forked from rust-lang/rust

This is a hack to support building targets that don't support jemalloc
alongside hosts that do. The jemalloc build is controlled by a feature
of the std crate, and if that feature changes between targets, it
invalidates the fingerprint of std's build script (this is a cargo
bug); so we must ensure that the feature set used by std is the same
across all targets, which means we have to build the alloc_jemalloc
crate for targets like emscripten, even if we don't use it.

Doing this step for the target results in the build system
trying to build rustc for asmjs, which doesn't work.

… objects

Initialize the asmjs backend for LLVM

add wrapper for discriminant_value, take 2

[This is rust-lang#34785 reopened, since @bors apparently gave up on that thread.]

add wrapper for discriminant_value intrinsic

Implementation of [RFC 1696](https://github.com/rust-lang/rfcs/blob/master/text/1696-discriminant.md).

Wraps the `discriminant_value` intrinsic under the name `std::mem::discriminant`. In order to avoid prematurely leaking information about the implementation of enums, the return value is an opaque type, generic over the enum type, which implements Copy, Clone, PartialEq, Eq, Hash, and Debug (notably not PartialOrd). There is currently no way to get the value out excepting printing the debug representation.

The wrapper is safe and can be stabilized soon as per discussion in rust-lang#24263.

cc @aturon
r? @nagisa

Resolve the callee type in check_call before autoderef

If the callee type is an associated type, then it needs to be normalized
before trying to deref it. This matches the behaviour of
`check_method_call` for autoderef behaviour in calls.

Fixes rust-lang#36786

…r=nrc

Fix ICE on some macros in const integer positions (e.g. `[u8; m!()]`)

Fixes rust-lang#36816.
r? @nrc

…hton

Clean up hasher discussion on HashMap

* We never want to make guarantees about protecting against attacks.
* "True randomness" is not the right terminology to be using in this
    context.
* There is significantly more nuance to the performance of SipHash than
    "somewhat slow".

r? @steveklabnik

Follow up to discussion on rust-lang#35371

impl Add<{str, Cow<str>}> for Cow<str>

cc rust-lang#35837

Change encode_utf{8,16}() to write to a buffer and panic if it's too small

cc rust-lang#27784

Should the "A buffer that's too small" examples be removed and replaced by tests?

Move MIR towards a single kind of local

This PR modifies MIR to handle function arguments (`Arg`), user-defined variable bindings (`Var`), compiler-generated temporaries (`Tmp`), as well as the return value pointer equally. All of them are replaced with a single `Local` type, a few functions for iterating over different kinds of locals, and a way to get the kind of local we're dealing with (mainly used in the constant qualification/propagation passes).

~~I haven't managed to fix one remaining issue: A `StorageDead` not getting emitted for a variable (see the `TODO` in the test). If that's fixed, this is basically good to go.~~ Found the issue (an off-by-one error), fix incoming.

r? @eddyb for changes to constant qualification and propagation I'm not quite sure about