Print hex dump of alloc on reading undef bytes
Here's a small addition I made locally to the UB diagnostics, in case you're interested in it. This PR calls `dump_alloc()` on the relevant allocation if Miri fails on UB due to reading undefined bytes. This came in handy when diagnosing such an issue in a large program using unsafe Rust, in part because it wasn't deterministic enough to use `-Zmiri-track-alloc-id=`. If you'd like to put this behind another -Z flag, let me know.
Handle std::sync::atomic::spin_loop_hint()
This PR adds support for `std::sync::atomic::spin_loop_hint()` by implementing the `llvm.x86.sse2.pause` intrinsic when the target is x86-based. It appears this is the first LLVM intrinsic in foreign_items, so I added a couple match blocks to handle it or fall through to the different OS-specific methods. I added a basic smoke test to `tests/run-pass/sync.rs`. I came across this by way of `crossbeam::utils::Backoff::spin()`, FWIW.
implement float_to_int_unchecked
@hanna-kruppe would be great if you could have a look at this.
`float.rs` tests legal casts. `test_cast` checks that both `as` casts and unchecked casts work (i.e., these are not saturating). The `compile-fail` tests should ensure that illegal casts via the intrinsic are detected as such.
Fixes https://github.com/rust-lang/miri/issues/1264
Implement `mach_timebase_info` for macOS
Since we return nanoseceonds instead of ticks from `mach_absolute_time`, we don't need to scale the absolute time
Fixes#1288
Even more float cast tests
Copy a bunch of float cast tests from https://github.com/WebAssembly/testsuite/blob/master/conversions.wast. I didn't do all of them though, too lazy... maybe we should have a wasm interpreter written in Rust and run that in Miri and use the wasm test suite directly that way? :P
