Currently, calling pow may panic in case of overflow, and the function
does not have non-panicking counterparts. Thus, it would be beneficial
to add those in.

rust-lang#41891

Previously, if the gdb command was available, but threw an error, compiletest would panic.  This is obviously not good. Now, gdb is treated as missing if calling `gdb --version` does not output anything on stdout.

Make a minimal commitment for stabilization.  More impls are likely in future, but are not necessary at this time.

This ensures that the entry function is never elided due to inlining, even with `inline(always)`. Fixes rust-lang#47783.

There were a couple of possible ways of addressing this issue; I simply picked the one that seemed most direct. A warning could be appropriate, but considering using inlining hints in other places it doesn't apply also throws no warnings, and it seems like an edge case anyway, I haven't added one for now.

This is what [Intel calls it][bmi1] and will [remove a special case][stdsimd]
when verifying intrinsics in stdsimd.

[bmi1]: https://software.intel.com/sites/landingpage/IntrinsicsGuide/#othertechs=BMI1
[stdsimd]: https://github.com/rust-lang-nursery/stdsimd/blob/bed25b2a9f3b28e6ea80de6d87842f739a2e2d58/crates/stdsimd-verify/tests/x86-intel.rs#L252-L258

…on-ice, r=michaelwoerister

Report non-standard compile flags on ICE

Some ICEs (such as the recent rust-lang#48248) only happens when a non-standard compiler flag is provided to rustc, but users don't always report the used flags. This can slow down reproducing the issue, so this PR shows all the non-standard compiler flags in the ICE error message.

For example, the output of rust-lang#48248 with this PR is:

```
error: internal compiler error: [...]

thread 'rustc' panicked at [...]
note: Run with `RUST_BACKTRACE=1` for a backtrace.

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: [...]

note: rustc 1.25.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -C link-dead-code
```

### Open questions

* At the moment, only `-C` and `-Z` flags are shown by default, and all the ones provided by cargo in a standard build are ignored: I did this to only show the flags that probably caused the ICE, and to remove some noise from the message. This removed flags like `opt-level` and `debuginfo` though, could those be useful for reproducing ICEs?

Add non-panicking variants of pow for integer types

Currently, calling pow may panic in case of overflow, and the function does not have non-panicking counterparts. Thus, it would be beneficial to add those in.

Closes rust-lang#48291.
Relevant tracking issue: rust-lang#48320

…rotatee, r=alexcrichton

Stabilize [T]::rotate_{left,right}

rust-lang#41891

…mpl-fix, r=QuietMisdreavus

Fix auto trait impl rustdoc ice

Fixes rust-lang#48463.

r? @QuietMisdreavus

…ichton

Add support for powerpc-unknown-linux-gnuspe

This PR adds support for the embedded PowerPC variant "e500". On Linux, this architecture is usually called "powerpcspe", it is a 32-bit PowerPC architecture. The main difference between normal 32-bit PowerPC and PowerPCSPE is the lack of Altivec instructions and the additional SPE instruction set.

This architecture is supported in Debian through an unofficial port.

…, r=michaelwoerister

Handle gdb command failure gracefully in compiletest

Previously, if the gdb command was available, but threw an error, compiletest would panic.  This is obviously not good. Now, gdb is treated as missing if calling `gdb --version` does not output anything on stdout.

…n, r=nikomatsakis

Restrict the Termination impls to simplify stabilization

Make a minimal commitment in preparation for stabilization.  More impls, or broader ones, are likely in future, but are not necessary at this time and are more controversial.

cc rust-lang#48453 (comment)
r? @nikomatsakis

…ster

Ensure main() always has external linkage

This ensures that the entry function is never elided due to inlining, even with `inline(always)`. Fixes rust-lang#47783.

There were a couple of possible ways of addressing this issue; I simply picked the one that seemed most direct. A warning could be appropriate, but considering using inlining hints in other places it doesn't apply also throws no warnings, and it seems like an edge case anyway, I haven't added one for now.

…ishearth

Fix error-format to properly send JSON to stdout

Since we take Cargo's JSON messages as well we need to specifically send
rustc's messages out so we don't hide them.

r? @Manishearth

…bank

Fix FreeBSD struct returning ABI.

FreeBSD has had a patch similar to this for a while. See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223047.

This reworks 6774e7a to be more specific about what `compute_abi_info` is checking for per target.

rustc: Rename `bmi` feature to `bmi1`

This is what [Intel calls it][bmi1] and will [remove a special case][stdsimd]
when verifying intrinsics in stdsimd.

[bmi1]: https://software.intel.com/sites/landingpage/IntrinsicsGuide/#othertechs=BMI1
[stdsimd]: https://github.com/rust-lang-nursery/stdsimd/blob/bed25b2a9f3b28e6ea80de6d87842f739a2e2d58/crates/stdsimd-verify/tests/x86-intel.rs#L252-L258

…ties, r=QuietMisdreavus

Rustdoc theme securities rust-lang#48381

Fixes rust-lang#48375.
Fixes rust-lang#48376.

…lexcrichton

Encode linker arguments as UTF-16 on MSVC platforms

This is a forward-port of rust-lang#48455 to the master branch