rollup merge of #18564 : nick29581/dxr-1a
rollup merge of #18568 : gamazeps/issue18551
rollup merge of #18572 : cakebaker/small_doc_changes
rollup merge of #18580 : hirschenberger/issue-17713
rollup merge of #18578 : japaric/clone
rollup merge of #18593 : hirschenberger/issue-18587

Conflicts:
	src/test/compile-fail/lint-exceeding-bitshifts.rs
auto merge of #18132 : P1start/rust/more-help, r=jakub-

Closes #18126.

At the moment this mostly only changes notes that are particularly help-oriented or directly suggest the user to do something to help messages, and does not change messages that simply explain an error message further. If it is decided that those messages should also be help messages, I can add them to this PR, but for now I’m excluding them as I believe that changing those messages might leave very few places where notes would be appropriate.
auto merge of #18596 : alexcrichton/rust/rollup, r=alexcrichton

Let's see if we can clear out the queue entirely today!
Implement flexible target specification

Removes all target-specific knowledge from rustc. Some targets have changed
during this, but none of these should be very visible outside of
cross-compilation. The changes make our targets more consistent.

iX86-unknown-linux-gnu is now only available as i686-unknown-linux-gnu. We
used to accept any value of X greater than 1. i686 was released in 1995, and
should encompass the bare minimum of what Rust supports on x86 CPUs.

The only two windows targets are now i686-pc-windows-gnu and
x86_64-pc-windows-gnu.

The iOS target has been renamed from arm-apple-ios to arm-apple-darwin.

A complete list of the targets we accept now:

arm-apple-darwin
arm-linux-androideabi
arm-unknown-linux-gnueabi
arm-unknown-linux-gnueabihf

i686-apple-darwin
i686-pc-windows-gnu
i686-unknown-freebsd
i686-unknown-linux-gnu

mips-unknown-linux-gnu
mipsel-unknown-linux-gnu

x86_64-apple-darwin
x86_64-unknown-freebsd
x86_64-unknown-linux-gnu
x86_64-pc-windows-gnu

Closes #16093

[breaking-change]
Use -m32 on 32bit Linux
Same fix for mac32
Same fix for dragonfly
Don't use pie on Android
Update some new use of the old targ_cfg
Update for collections reform
auto merge of #16156 : cmr/rust/target-spec, r=alexcrichton

See commit message.
Guide: explains the enum/match relationship

Closes #18169
Translate SIMD construction as `insertelement`s and a single store.

This almost completely avoids GEPi's and pointer manipulation,
postponing it until the end with one big write of the whole vector. This
leads to a small speed-up in compilation, and makes it easier for LLVM
to work with the values, e.g. with `--opt-level=0`,

    pub fn foo() -> f32x4 {
        f32x4(0.,0.,0.,0.)
    }

was previously compiled to

    define <4 x float> @_ZN3foo20h74913e8b13d89666eaaE() unnamed_addr #0 {
    entry-block:
      %sret_slot = alloca <4 x float>
      %0 = getelementptr inbounds <4 x float>* %sret_slot, i32 0, i32 0
      store float 0.000000e+00, float* %0
      %1 = getelementptr inbounds <4 x float>* %sret_slot, i32 0, i32 1
      store float 0.000000e+00, float* %1
      %2 = getelementptr inbounds <4 x float>* %sret_slot, i32 0, i32 2
      store float 0.000000e+00, float* %2
      %3 = getelementptr inbounds <4 x float>* %sret_slot, i32 0, i32 3
      store float 0.000000e+00, float* %3
      %4 = load <4 x float>* %sret_slot
      ret <4 x float> %4
    }

but now becomes

    define <4 x float> @_ZN3foo20h74913e8b13d89666eaaE() unnamed_addr #0 {
    entry-block:
      ret <4 x float> zeroinitializer
    }
rustc: Support stability attributes on crates

This commit adds support for linting `extern crate` statements for stability
attributes attached to the crate itself. This is likely to be the mechanism used
to deny access to experimental crates that are part of the standard
distribution.

cc #18585
auto merge of #18497 : gamazeps/rust/enumsmatch, r=steveklabnik

Closes #18169