Add target thumbv7a-pc-windows-msvc
This is an early draft of support for Windows/ARM. To test it,
1. Install Visual Studio 2017 and Windows SDK version 17134.
1. Obtain alexcrichton/xz2-rs#35, rust-lang-nursery/compiler-builtins#256, and the fix for [LLVM Bug 38620](https://bugs.llvm.org/show_bug.cgi?id=38620).
2. Open a command prompt and run
```
set CC_thumbv7a-pc-windows-msvc=C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\VC\Tools\MSVC\14.11.25503\bin\HostX64\arm\CL.exe
set CFLAGS_thumbv7a-pc-windows-msvc=/D_ARM_WINAPI_PARTITION_DESKTOP_SDK_AVAILABLE=1 /nologo
c:\python27\python.exe x.py build --host x86_64-pc-windows-msvc --build x86_64-pc-windows-msvc --target thumbv7a-pc-windows-msvc
```
It will build the stage 2 compiler, but fail building stage 2 test. To build an executable targeting windows/arm,
1. Copy `build\x86_64-pc-windows-msvc\stage0\bin\cargo.exe` to `build\x86_64-pc-windows-msvc\stage2\bin`
2. Open a command prompt and run
```
"C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
set PATH=build\x86_64-pc-windows-msvc\stage2\bin;%PATH%
cargo new hello
cd hello
cargo build --target thumbv7a-pc-windows-msvc –release
```
Copy target\thumbv7a-pc-windows-msvc\release\hello.exe to your platform and run.
There are a number of open issues that I'm hoping to get help with:
- Error when compiling the `test` crate: `error: cannot link together two panic runtimes: panic_abort and panic_unwind`
- Warnings when building the compiler_builtins crate: `warning: cl : Command line warning D9002 : ignoring unknown option '-fvisibility=hidden'`. It looks like the build system is passing GCC-style flags to MSVC.
- How to specify the LIBPATH entries for ARM. Right now they are hardcoded as absolute paths in the target spec.
This pull request depends on
- alexcrichton/xz2-rs#35 - update vcxproj to Visual Studio 2017
- rust-lang-nursery/compiler-builtins#256 - fix compile errors when building for windows/arm
- [Bug 38620 - ARM: Incorrect COFF relocation type for thumb bl instruction](https://bugs.llvm.org/show_bug.cgi?id=38620)
This PR updates #52659
This requires the following changes.
- It moves parts of bitslice.rs into bitvec.rs: `bitwise()`,
`BitwiseOperator`, `bits_to_string()`.
- It changes `IdxSet` to just be a wrapper around `BitArray`.
- It changes `BitArray` and `BitVec` to use `usize` words instead of
`u128` words. (`BitSlice` and `IdxSet` already use `usize`.) Local
profiling showed `usize` was better.
- It moves some operations from `IdxSet` into `BitArray`:
`new_filled()`, `clear()`, `set_up_to()`, `trim_to()` (renamed
`clear_above()`), `words()` and `words_mut()`, `encode()` and
`decode(). The `IdxSet` operations now just call the `BitArray`
operations.
- It replaces `BitArray`'s iterator implementation with `IdxSet`'s,
because the latter is more concise. It also removes the buggy
`size_hint` function from `BitArray`'s iterator, which counted the
number of *words* rather than the number of *bits*. `IdxSet`'s
iterator is now just a thin wrapper around `BitArray`'s iterator.
- It moves some unit tests from `indexed_set.rs` to `bitvec.rs`.
resolve: Future proof derive helper attributes
Derive helpers no longer require going through recovery mode (fixes https://github.com/rust-lang/rust/issues/53481).
They also report an error if they are ambiguous with any other macro in scope, so we can resolve the question about their exact priority sometime later (cc https://github.com/rust-lang/rust/issues/52226).
Previously the code below would not be guaranteed to exit when the first
spawned thread took the `return, // already unparked` path because there
was no write to synchronize with a read in `park`.
```
use std::sync::atomic::{AtomicBool, Ordering};
use std:🧵:{current, spawn, park};
static FLAG: AtomicBool = AtomicBool::new(false);
fn main() {
let thread_0 = current();
spawn(move || {
FLAG.store(true, Ordering::Relaxed);
thread_0.unpark();
});
let thread_0 = current();
spawn(move || {
thread_0.unpark();
});
while !FLAG.load(Ordering::Relaxed) {
park();
}
}
```
