rustc: Don't inline in CGUs at -O0

This commit tweaks the behavior of inlining functions into multiple codegen
units when rustc is compiling in debug mode. Today rustc will unconditionally
treat `#[inline]` functions by translating them into all codegen units that
they're needed within, marking the linkage as `internal`. This commit changes
the behavior so that in debug mode (compiling at `-O0`) rustc will instead only
translate `#[inline]` functions into *one* codegen unit, forcing all other
codegen units to reference this one copy.

The goal here is to improve debug compile times by reducing the amount of
translation that happens on behalf of multiple codegen units. It was discovered
in #44941 that increasing the number of codegen units had the adverse side
effect of increasing the overal work done by the compiler, and the suspicion
here was that the compiler was inlining, translating, and codegen'ing more
functions with more codegen units (for example `String` would be basically
inlined into all codegen units if used). The strategy in this commit should
reduce the cost of `#[inline]` functions to being equivalent to one codegen
unit, which is only translating and codegen'ing inline functions once.

Collected [data] shows that this does indeed improve the situation from [before]
as the overall cpu-clock time increases at a much slower rate and when pinned to
one core rustc does not consume significantly more wall clock time than with one
codegen unit.

One caveat of this commit is that the symbol names for inlined functions that
are only translated once needed some slight tweaking. These inline functions
could be translated into multiple crates and we need to make sure the symbols
don't collideA so the crate name/disambiguator is mixed in to the symbol name
hash in these situations.

[data]: https://github.com/rust-lang/rust/issues/44941#issuecomment-334880911
[before]: https://github.com/rust-lang/rust/issues/44941#issuecomment-334583384

rustc: Reduce default CGUs to 16

Rationale explained in the included comment as well as #44941

Remove support for the PNaCl target (le32-unknown-nacl)

This removes support for the `le32-unknown-nacl` target which is currently supported by rustc on tier 3. Despite the "nacl" in the name, the target doesn't output native code (x86, ARM, MIPS), instead it outputs binaries in the PNaCl format.

There are two reasons for the removal:

* Google [has announced](https://blog.chromium.org/2017/05/goodbye-pnacl-hello-webassembly.html) deprecation of the PNaCl format. The suggestion is to migrate to wasm. Happens we already have a wasm backend!
* Our PNaCl LLVM backend is provided by the fastcomp patch set that the LLVM fork used by rustc contains in addition to vanilla LLVM (`src/llvm/lib/Target/JSBackend/NaCl`). Upstream LLVM doesn't have PNaCl support. Removing PNaCl support will enable us to move away from fastcomp (#44006) and have a lighter set of patches on top of upstream LLVM inside our LLVM fork. This will help distribution packagers of Rust.

Fixes #42420

rustc: Don't create empty codegen units

This'll end up just creating a bunch of object files that otherwise wouldn't
exist, so skip that extra work if possible.

rustc_trans: do not set NoCapture for anonymous lifetime &T arguments.

This was both unsound (due to lifetime elision & unsafe code) and dead code (we erase lifetimes).

r? @nikomatsakis

zircon: the type of zx_handle_t is now unsigned

This is a kernel ABI change that landed today. I noticed some other ABI
issues and have left a note to cleanup once they are better defined.

MIR-borrowck: gather and signal any move errors

When building up the `MoveData` structure for a given MIR, also accumulate any erroneous actions, and then report all of those errors when the construction is complete.

This PR adds a host of move-related error constructor methods to `trait BorrowckErrors`. I think I got the notes right; but we should plan to audit all of the notes before turning MIR-borrowck on by default.

Fix #44830

Fix some E-needstest issues.

Also ignore `attr-on-trait` test on stage-1 to keep `./x.py test --stage 1` successful.

Fixes #30355.
Fixes #33241.
Fixes #36400.
Fixes #37887.
Fixes #44578.

Add -Zmutable-noalias flag

We disabled noalias on mutable references a long time ago when it was clear that llvm was incorrectly handling this in relation to unwinding edges.

Since then, a few things have happened:

* llvm has cleaned up a bunch of the issues (I'm told)
* we've added a nounwind codegen option

As such, I would like to add this -Z flag so that we can evaluate if the codegen bugs still exist, and if this significantly affects the codegen of different projects, with an eye towards permanently re-enabling it (or at least making it a stable option).

Add builder for Solaris and merge it with Fuchsia's builder

The new Solaris builder can be used to build rust-std.

The dilos illumos distribution was chosen, because illumos is free software
as opposed to Oracle Solaris and dilos is the only illumos distribution that
supports x86_64 and sparcv9 at the same level.

Rollup of 10 pull requests

- Successful merges: #45018, #45042, #45052, #45053, #45058, #45060, #45081, #45083, #45090, #45094
- Failed merges:

enable strict alignment (+strict-align) on ARMv6

As discovered in #44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6
Linux *seems* to have no problem with unaligned accesses but this is because the kernel is stepping
in to fix each unaligned memory access -- this incurs in a performance penalty.

This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with
ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record,
clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or
NetBSD.

closes #44538
r? @alexcrichton

Document that `-C ar=PATH` doesn't do anything

Are there any plans to use an external archiver in the future?
IIRC, it was used before, but its use was replaced with LLVM's built-in archive management machinery. I can't found a relevant PR though. EDIT: Found it - https://github.com/rust-lang/rust/pull/26926!

The `-C` option is stable so it still can't be removed right away even if there are no plans to use it (but maybe it can be deprecated?).
Target specifications have a field for archiver as well, which is unused too (these ones are unstable, so I guess it can be removed).

r? @alexcrichton

Add read_to_end implementation to &[u8]'s Read impl

The default impl for read_to_end does a bunch of bookkeeping
that isn't necessary for slices and is about 4 times slower
on my machine.

The following benchmark takes about 30 ns before this change and about 7 ns after:

```
#[bench]
fn bench_read_std(b: &mut Bencher) {
    let data = vec![0u8; 100];
    let mut v = Vec::with_capacity(200);
    b.iter(|| {
        let mut s = data.as_slice();
        v.clear();
        s.read_to_end(&mut v).unwrap();
    });
}
```

This solves the easy part of  https://github.com/rust-lang/rust/issues/44819 (I think extending this to `Take<&[u8]> `would require specialization)

fmt: misc cleanup

Add a semicolon to span for ast::Local

Fix typo, per #45057.

This looks like a simple string -- one character -- fix.  Given that I'm currently running low on battery, I have not actually compiled and tested this.  But I am fully confident this passes muster.  If not, I'll be maintainer-educated, yes?  ;-)

Add missing links for AtomicBool

r? @rust-lang/docs

Modify Rc/Arc language around mutability

There are a few exceptions to the rule that Arc/Rc are immutable. Rather
than dig into the details, add "generally" to hint at this difference,
as it's kind of a distraction at this point in the docs.

Additionally, Arc's docs were slightly different here generally, so add
in both the existing language and the exception.

Fixes #44105

Update trait summaries for std::fmt

This patch is part of #29355.

r? @steveklabnik

incr.comp.: Fix infinite recursion in Debug implementation of DepNode

Small bug fix. Depends on #44901 to land first.

groundwork for rustc_clean/dirty improvements

This is a WIP PR that needs mentoring from @michaelwoerister.

There are several TODOs but no outstanding questions (except for the main one -- **is this the right approach?**)

This is the plumbing for supporing groups in `rustc_clean(labels="...")`, as well as supporting an `except="..."` which will remove the excepted labels in the "clean" check and then assert that they are dirty (this is still TODO).

See the code TODO's and example comments for a rough design.

I'd like to know if this is the design you would like to do, and then I can go about actually filling out the groups and implementing the remaining logic.

This commit tweaks the behavior of inlining functions into multiple codegen
units when rustc is compiling in debug mode. Today rustc will unconditionally
treat `#[inline]` functions by translating them into all codegen units that
they're needed within, marking the linkage as `internal`. This commit changes
the behavior so that in debug mode (compiling at `-O0`) rustc will instead only
translate `#[inline]` functions into *one* codegen unit, forcing all other
codegen units to reference this one copy.

The goal here is to improve debug compile times by reducing the amount of
translation that happens on behalf of multiple codegen units. It was discovered
in #44941 that increasing the number of codegen units had the adverse side
effect of increasing the overal work done by the compiler, and the suspicion
here was that the compiler was inlining, translating, and codegen'ing more
functions with more codegen units (for example `String` would be basically
inlined into all codegen units if used). The strategy in this commit should
reduce the cost of `#[inline]` functions to being equivalent to one codegen
unit, which is only translating and codegen'ing inline functions once.

Collected [data] shows that this does indeed improve the situation from [before]
as the overall cpu-clock time increases at a much slower rate and when pinned to
one core rustc does not consume significantly more wall clock time than with one
codegen unit.

One caveat of this commit is that the symbol names for inlined functions that
are only translated once needed some slight tweaking. These inline functions
could be translated into multiple crates and we need to make sure the symbols
don't collideA so the crate name/disambiguator is mixed in to the symbol name
hash in these situations.

[data]: https://github.com/rust-lang/rust/issues/44941#issuecomment-334880911
[before]: https://github.com/rust-lang/rust/issues/44941#issuecomment-334583384

Allow atomic operations up to 32 bits

The ARMv5te platform does not have instruction-level support for atomics, however the kernel provides [user space helpers] which can be used to perform atomic operations. When linked with `libgcc`, the atomic symbols needed by Rust will be provided, rather than CPU level intrinsics.

[user space helpers]: https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt

32-bit versions of these kernel level helpers were introduced in Linux Kernel 2.6.12, and 64-bit version of these kernel level helpers were introduced in Linux Kernel 3.1. I have selected 32 bit versions as std currently only requires Linux version 2.6.18 and above as far as I am aware.

As this target is specifically linux and gnueabi, it is reasonable to assume the Linux Kernel and libc will be available for the target. There is a large performance penalty, as we are not using CPU level intrinsics, however this penalty is likely preferable to not having the target at all.

I have used this change in a custom target (along with xargo) to build std, as well as a number of higher level crates.

## Additional information

For reference, here is what a a code snippet decompiles to:

```rust
use std::sync::atomic::{AtomicIsize, Ordering};

#[no_mangle]
pub extern fn foo(a: &AtomicIsize) -> isize {

    a.fetch_add(1, Ordering::SeqCst)
}
```

```
Disassembly of section .text.foo:

00000000 <foo>:
   0:	e92d4800 	push	{fp, lr}
   4:	e3a01001 	mov	r1, #1
   8:	ebfffffe 	bl	0 <__sync_fetch_and_add_4>
   c:	e8bd8800 	pop	{fp, pc}
```

Which in turn is provided by `libgcc.a`, which has code which looks like this:

```
Disassembly of section .text:

00000000 <__sync_fetch_and_add_4>:
       0:	e92d40f8 	push	{r3, r4, r5, r6, r7, lr}
       4:	e1a05000 	mov	r5, r0
       8:	e1a07001 	mov	r7, r1
       c:	e59f6028 	ldr	r6, [pc, #40]	; 3c <__sync_fetch_and_add_4+0x3c>
      10:	e5954000 	ldr	r4, [r5]
      14:	e1a02005 	mov	r2, r5
      18:	e1a00004 	mov	r0, r4
      1c:	e0841007 	add	r1, r4, r7
      20:	e1a0e00f 	mov	lr, pc
      24:	e12fff16 	bx	r6
      28:	e3500000 	cmp	r0, #0
      2c:	1afffff7 	bne	10 <__sync_fetch_and_add_4+0x10>
      30:	e1a00004 	mov	r0, r4
      34:	e8bd40f8 	pop	{r3, r4, r5, r6, r7, lr}
      38:	e12fff1e 	bx	lr
      3c:	ffff0fc0 	.word	0xffff0fc0
```

Where you can see the reference to `0xffff0fc0`, which is provided by the [user space helpers].

rustc: Implement ThinLTO

This commit is an implementation of LLVM's ThinLTO for consumption in rustc
itself. Currently today LTO works by merging all relevant LLVM modules into one
and then running optimization passes. "Thin" LTO operates differently by having
more sharded work and allowing parallelism opportunities between optimizing
codegen units. Further down the road Thin LTO also allows *incremental* LTO
which should enable even faster release builds without compromising on the
performance we have today.

This commit uses a `-Z thinlto` flag to gate whether ThinLTO is enabled. It then
also implements two forms of ThinLTO:

* In one mode we'll *only* perform ThinLTO over the codegen units produced in a
  single compilation. That is, we won't load upstream rlibs, but we'll instead
  just perform ThinLTO amongst all codegen units produced by the compiler for
  the local crate. This is intended to emulate a desired end point where we have
  codegen units turned on by default for all crates and ThinLTO allows us to do
  this without performance loss.

* In anther mode, like full LTO today, we'll optimize all upstream dependencies
  in "thin" mode. Unlike today, however, this LTO step is fully parallelized so
  should finish much more quickly.

There's a good bit of comments about what the implementation is doing and where
it came from, but the tl;dr; is that currently most of the support here is
copied from upstream LLVM. This code duplication is done for a number of
reasons:

* Controlling parallelism means we can use the existing jobserver support to
  avoid overloading machines.
* We will likely want a slightly different form of incremental caching which
  integrates with our own incremental strategy, but this is yet to be
  determined.
* This buys us some flexibility about when/where we run ThinLTO, as well as
  having it tailored to fit our needs for the time being.
* Finally this allows us to reuse some artifacts such as our `TargetMachine`
  creation, where all our options we used today aren't necessarily supported by
  upstream LLVM yet.

My hope is that we can get some experience with this copy/paste in tree and then
eventually upstream some work to LLVM itself to avoid the duplication while
still ensuring our needs are met. Otherwise I fear that maintaining these
bindings may be quite costly over the years with LLVM updates!

The default impl for read_to_end does a bunch of bookkeeping
that isn't necessary for slices and is about 4 times slower
on my machine.

Fnty args rustdoc

Fixes #44570.

cc @QuietMisdreavus
cc @rust-lang/dev-tools

Considering the impact on the `hir` libs, I'll put @EddyB as reviewer.

r? @EddyB

As discovered in #44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6
Linux *seems* to have no problem with unaligned accesses but this is because the kernel is stepping
in to fix each unaligned memory access -- this incurs in a performance penalty.

This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with
ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record,
clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or
NetBSD.

This commit is an implementation of LLVM's ThinLTO for consumption in rustc
itself. Currently today LTO works by merging all relevant LLVM modules into one
and then running optimization passes. "Thin" LTO operates differently by having
more sharded work and allowing parallelism opportunities between optimizing
codegen units. Further down the road Thin LTO also allows *incremental* LTO
which should enable even faster release builds without compromising on the
performance we have today.

This commit uses a `-Z thinlto` flag to gate whether ThinLTO is enabled. It then
also implements two forms of ThinLTO:

* In one mode we'll *only* perform ThinLTO over the codegen units produced in a
  single compilation. That is, we won't load upstream rlibs, but we'll instead
  just perform ThinLTO amongst all codegen units produced by the compiler for
  the local crate. This is intended to emulate a desired end point where we have
  codegen units turned on by default for all crates and ThinLTO allows us to do
  this without performance loss.

* In anther mode, like full LTO today, we'll optimize all upstream dependencies
  in "thin" mode. Unlike today, however, this LTO step is fully parallelized so
  should finish much more quickly.

There's a good bit of comments about what the implementation is doing and where
it came from, but the tl;dr; is that currently most of the support here is
copied from upstream LLVM. This code duplication is done for a number of
reasons:

* Controlling parallelism means we can use the existing jobserver support to
  avoid overloading machines.
* We will likely want a slightly different form of incremental caching which
  integrates with our own incremental strategy, but this is yet to be
  determined.
* This buys us some flexibility about when/where we run ThinLTO, as well as
  having it tailored to fit our needs for the time being.
* Finally this allows us to reuse some artifacts such as our `TargetMachine`
  creation, where all our options we used today aren't necessarily supported by
  upstream LLVM yet.

My hope is that we can get some experience with this copy/paste in tree and then
eventually upstream some work to LLVM itself to avoid the duplication while
still ensuring our needs are met. Otherwise I fear that maintaining these
bindings may be quite costly over the years with LLVM updates!

Fix TcpStream::local_addr docs example code

The local address's port is not 8080 in this example, that's the remote peer address port. On my machine, the local address is different every time, so I've changed `assert_eq` to only test the IP address

Fix issue #44731.

Also excludes `impl Trait` from everybody_loops if it appears in the path.

Fixes #44731.

{compiler-builtins,libc} shim cleanup

~~Depends on https://github.com/rust-lang/libc/pull/764; opening early for feedback.~~ r? @alexcrichton

implement pattern-binding-modes RFC

See the [RFC] and [tracking issue].

[tracking issue]: #42640
[RFC]: https://github.com/rust-lang/rfcs/blob/491e0af/text/2005-match-ergonomics.md