rust/tests/ui/lto/auxiliary/thin-lto-inlines-aux.rs

// no-prefer-dynamic

#![crate_type = "rlib"]

pub fn bar() -> u32 {
    3
}
rustc: Implement ThinLTO This commit is an implementation of LLVM's ThinLTO for consumption in rustc itself. Currently today LTO works by merging all relevant LLVM modules into one and then running optimization passes. "Thin" LTO operates differently by having more sharded work and allowing parallelism opportunities between optimizing codegen units. Further down the road Thin LTO also allows incremental LTO which should enable even faster release builds without compromising on the performance we have today. This commit uses a `-Z thinlto` flag to gate whether ThinLTO is enabled. It then also implements two forms of ThinLTO: * In one mode we'll only perform ThinLTO over the codegen units produced in a single compilation. That is, we won't load upstream rlibs, but we'll instead just perform ThinLTO amongst all codegen units produced by the compiler for the local crate. This is intended to emulate a desired end point where we have codegen units turned on by default for all crates and ThinLTO allows us to do this without performance loss. * In anther mode, like full LTO today, we'll optimize all upstream dependencies in "thin" mode. Unlike today, however, this LTO step is fully parallelized so should finish much more quickly. There's a good bit of comments about what the implementation is doing and where it came from, but the tl;dr; is that currently most of the support here is copied from upstream LLVM. This code duplication is done for a number of reasons: * Controlling parallelism means we can use the existing jobserver support to avoid overloading machines. * We will likely want a slightly different form of incremental caching which integrates with our own incremental strategy, but this is yet to be determined. * This buys us some flexibility about when/where we run ThinLTO, as well as having it tailored to fit our needs for the time being. * Finally this allows us to reuse some artifacts such as our `TargetMachine` creation, where all our options we used today aren't necessarily supported by upstream LLVM yet. My hope is that we can get some experience with this copy/paste in tree and then eventually upstream some work to LLVM itself to avoid the duplication while still ensuring our needs are met. Otherwise I fear that maintaining these bindings may be quite costly over the years with LLVM updates! 2017-07-23 10:14:38 -05:00			`// no-prefer-dynamic`

			`#![crate_type = "rlib"]`

			`pub fn bar() -> u32 {`
			`3`
			`}`