This replaces the wrapper around the runtime RNG with a pure Rust implementation of the same algorithm. This is much faster (up to 5x), and is hopefully safer.
There is still (a little) room for optimisation: testing by summing 100,000,000 random `u32`s indicates this is about ~~40-50%~~ 10% slower than the pure C implementation (running as standalone executable, not in the runtime).
(Only 6d50d55 is part of this PR, the first two are from #6058, but are required for the rt rng to be correct to compare against in the tests.)
This replaces the wrapper around the runtime RNG with a pure Rust
implementation of the same algorithm. This is faster (up to 5x), and
is hopefully safer.
There is still much room for optimisation: testing by summing 100,000,000
random `u32`s indicates this is about 40-50% slower than the pure C
implementation (running as standalone executable, not in the runtime).
This moves all the basic random value generation into the Rand instances for
each type and then removes the `gen_int`, `gen_char` (etc) methods on RngUtil,
leaving only the generic `gen` and the more specialised methods.
Also, removes some imports that are redundant due to a `use core::prelude::*`
statement.
Closes#3083.
This takes a similar approach to #5797 where a set is present on the `tcx` of used mutable definitions. Everything is by default warned about, and analyses must explicitly add mutable definitions to this set so they're not warned about.
Most of this was pretty straightforward, although there was one caveat that I ran into when implementing it. Apparently when the old modes are used (or maybe `legacy_modes`, I'm not sure) some different code paths are taken to cause spurious warnings to be issued which shouldn't be issued. I'm not really sure how modes even worked, so I was having a lot of trouble tracking this down. I figured that because they're a legacy thing that I'd just de-mode the compiler so that the warnings wouldn't be a problem anymore (or at least for the compiler).
Other than that, the entire compiler compiles without warnings of unused mutable variables. To prevent bad warnings, #5965 should be landed (which in turn is waiting on #5963) before landing this. I figured I'd stick it out for review anyway though.
