Add test for #18908
Special-case transmute for primitive, SIMD & pointer types.

This detects (a subset of) the cases when `transmute::<T, U>(x)` can be
lowered to a direct `bitcast T x to U` in LLVM. This assists with
efficiently handling a SIMD vector as multiple different types,
e.g. swapping bytes/words/double words around inside some larger vector
type.

C compilers like GCC and Clang handle integer vector types as `__m128i`
for all widths, and implicitly insert bitcasts as required. This patch
allows Rust to express this, even if it takes a bit of `unsafe`, whereas
previously it was impossible to do at all without inline assembly.

Example:

    pub fn reverse_u32s(u: u64x2) -> u64x2 {
        unsafe {
            let tmp = mem::transmute::<_, u32x4>(u);
            let swapped = u32x4(tmp.3, tmp.2, tmp.1, tmp.0);
            mem::transmute::<_, u64x2>(swapped)
        }
    }

Compiling with `--opt-level=3` gives:

Before

    define <2 x i64> @_ZN12reverse_u32s20hbdb206aba18a03d8tbaE(<2 x i64>) unnamed_addr #0 {
    entry-block:
      %1 = bitcast <2 x i64> %0 to i128
      %u.0.extract.trunc = trunc i128 %1 to i32
      %u.4.extract.shift = lshr i128 %1, 32
      %u.4.extract.trunc = trunc i128 %u.4.extract.shift to i32
      %u.8.extract.shift = lshr i128 %1, 64
      %u.8.extract.trunc = trunc i128 %u.8.extract.shift to i32
      %u.12.extract.shift = lshr i128 %1, 96
      %u.12.extract.trunc = trunc i128 %u.12.extract.shift to i32
      %2 = insertelement <4 x i32> undef, i32 %u.12.extract.trunc, i64 0
      %3 = insertelement <4 x i32> %2, i32 %u.8.extract.trunc, i64 1
      %4 = insertelement <4 x i32> %3, i32 %u.4.extract.trunc, i64 2
      %5 = insertelement <4 x i32> %4, i32 %u.0.extract.trunc, i64 3
      %6 = bitcast <4 x i32> %5 to <2 x i64>
      ret <2 x i64> %6
    }

    _ZN12reverse_u32s20hbdb206aba18a03d8tbaE:
    	.cfi_startproc
    	movd	%xmm0, %rax
    	punpckhqdq	%xmm0, %xmm0
    	movd	%xmm0, %rcx
    	movq	%rcx, %rdx
    	shrq	$32, %rdx
    	movq	%rax, %rsi
    	shrq	$32, %rsi
    	movd	%eax, %xmm0
    	movd	%ecx, %xmm1
    	punpckldq	%xmm0, %xmm1
    	movd	%esi, %xmm2
    	movd	%edx, %xmm0
    	punpckldq	%xmm2, %xmm0
    	punpckldq	%xmm1, %xmm0
    	retq

After

    define <2 x i64> @_ZN12reverse_u32s20hbdb206aba18a03d8tbaE(<2 x i64>) unnamed_addr #0 {
    entry-block:
      %1 = bitcast <2 x i64> %0 to <4 x i32>
      %2 = shufflevector <4 x i32> %1, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
      %3 = bitcast <4 x i32> %2 to <2 x i64>
      ret <2 x i64> %3
    }

    _ZN12reverse_u32s20hbdb206aba18a03d8tbaE:
    	.cfi_startproc
    	pshufd	$27, %xmm0, %xmm0
    	retq
Rename assert_eq arguments to left and right.

The names expected and actual are not used anymore in the output. It also
removes the confusion that the argument order is the opposite of junit.
Rollback accidental documentation changes

These probably happened during the merge of the commit that made `Copy` opt-in.

Also, convert the last occurence of `/**` to `///` in `src/libstd/num/strconv.rs`
doc: grammar fix
Add doctests for `iter_mut` and `into_iter` of BTreeMap.

Add spacing as dictated by standard rust code style.
Remove references to traits that no longer exist

This specifically means:
- `Deque`
- `Map`
- `Set`
Update sample code to use `getopts::usage` in `print_usage`
Fix an ICE when trying to resolve a struct variant

Unlike a tuple variant constructor which can be called as a function, a
struct variant constructor is not a function, so cannot be called.

If the user tries to assign the constructor to a variable, an ICE
occurs, because there is no way to use it later. So we should stop the
constructor from being used like that.

A similar mechanism already exists for a normal struct, as it prohibits
a struct from being resolved. This commit does the same for a struct
variant.

This commit also includes some changes to the existing tests.

Fixes #19452.
Fix po4a conf file

This line was declared twice, which causes the build of i10n docs to
fail.
Fix inappropriate ## headings

Fixes #15499.
auto merge of #19705 : brson/rust/fix-install, r=alexcrichton
Fix up some {ignore} and {notrust}s

These should be properly annotated instead.

Fixes #16219.
Change default installation directory to %SYSTEMDRIVE%\Rust.
Modify user PATH, rather than system PATH.
auto merge of #19294 : huonw/rust/transmute-inplace, r=nikomatsakis

This detects (a subset of) the cases when `transmute::<T, U>(x)` can be
lowered to a direct `bitcast T x to U` in LLVM. This assists with
efficiently handling a SIMD vector as multiple different types,
e.g. swapping bytes/words/double words around inside some larger vector
type.

C compilers like GCC and Clang handle integer vector types as `__m128i`
for all widths, and implicitly insert bitcasts as required. This patch
allows Rust to express this, even if it takes a bit of `unsafe`, whereas
previously it was impossible to do at all without inline assembly.

Example:

    pub fn reverse_u32s(u: u64x2) -> u64x2 {
        unsafe {
            let tmp = mem::transmute::<_, u32x4>(u);
            let swapped = u32x4(tmp.3, tmp.2, tmp.1, tmp.0);
            mem::transmute::<_, u64x2>(swapped)
        }
    }

Compiling with `--opt-level=3` gives:

Before

    define <2 x i64> @_ZN12reverse_u32s20hbdb206aba18a03d8tbaE(<2 x i64>) unnamed_addr #0 {
    entry-block:
      %1 = bitcast <2 x i64> %0 to i128
      %u.0.extract.trunc = trunc i128 %1 to i32
      %u.4.extract.shift = lshr i128 %1, 32
      %u.4.extract.trunc = trunc i128 %u.4.extract.shift to i32
      %u.8.extract.shift = lshr i128 %1, 64
      %u.8.extract.trunc = trunc i128 %u.8.extract.shift to i32
      %u.12.extract.shift = lshr i128 %1, 96
      %u.12.extract.trunc = trunc i128 %u.12.extract.shift to i32
      %2 = insertelement <4 x i32> undef, i32 %u.12.extract.trunc, i64 0
      %3 = insertelement <4 x i32> %2, i32 %u.8.extract.trunc, i64 1
      %4 = insertelement <4 x i32> %3, i32 %u.4.extract.trunc, i64 2
      %5 = insertelement <4 x i32> %4, i32 %u.0.extract.trunc, i64 3
      %6 = bitcast <4 x i32> %5 to <2 x i64>
      ret <2 x i64> %6
    }

    _ZN12reverse_u32s20hbdb206aba18a03d8tbaE:
    	.cfi_startproc
    	movd	%xmm0, %rax
    	punpckhqdq	%xmm0, %xmm0
    	movd	%xmm0, %rcx
    	movq	%rcx, %rdx
    	shrq	$32, %rdx
    	movq	%rax, %rsi
    	shrq	$32, %rsi
    	movd	%eax, %xmm0
    	movd	%ecx, %xmm1
    	punpckldq	%xmm0, %xmm1
    	movd	%esi, %xmm2
    	movd	%edx, %xmm0
    	punpckldq	%xmm2, %xmm0
    	punpckldq	%xmm1, %xmm0
    	retq

After

    define <2 x i64> @_ZN12reverse_u32s20hbdb206aba18a03d8tbaE(<2 x i64>) unnamed_addr #0 {
    entry-block:
      %1 = bitcast <2 x i64> %0 to <4 x i32>
      %2 = shufflevector <4 x i32> %1, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
      %3 = bitcast <4 x i32> %2 to <2 x i64>
      ret <2 x i64> %3
    }

    _ZN12reverse_u32s20hbdb206aba18a03d8tbaE:
    	.cfi_startproc
    	pshufd	$27, %xmm0, %xmm0
    	retq
Fix two bugs in HRTB: 1. Categorize early-vs-late bindings on impls when constructing    generics, so that we don't add unnecessary region parameters. 2. Correct the DeBruijn indices when substituting the self type    into the method signature.

Previously, the DeBruijn index for the self type was not being
adjusted to account for the fn binder. This mean that when late-bound
regions were instantiated, you sometimes wind up with two distinct
lifetimes.

Fixes #19537.
During method resolution, only reborrow if we are not doing an auto-ref.
The current behavior leads to adjustments like `&&*` being applied
instead of just `&` (when the unmodified receiver is a `&T` or an `&mut
T`). This causes both safety errors and unexpected behavior. The safety
errors result from regionck not being prepared for auto-ref-ref-like
adjustments; this is worth fixing on its own, but I think the best way
to do it is to modify regionck to use expr-use-visitor (and fix
expr-use-visitor as well, which I don't think properly invokes `borrow`
for each level of auto-ref), and for now it's simpler to just not
produce the adjustment in question. (I have a separate patch porting
regionck to use exprusevisitor for a different bug, so that is coming.)
Fix an incorrect type annotation (shadowed lifetime parameter) that was masked by
these bugs.
Update intro.md
gdb < RUST_BACKTRACE

Fixes #19717