Commits on May 4, 2020

1. Don't force rustc to do codegen for LTO builds …

   This commit updates Cargo's implementation of LTO builds to do less work
   and hopefully be faster when doing a cold build. Additionaly this should
   save space on disk! The general idea is that the compiler does not need
   object files if it's only going to perform LTO with some artifacts. In
   this case all rustc needs to do is load bitcode from dependencies. This
   means that if you're doing an LTO build generating object code for
   intermediate dependencies is just wasted time!
   
   Here Cargo is updated with more intrusive knowledge about LTO. Cargo
   will now analyze the dependency graph to figure out which crates are
   being compiled with LTO, and then it will figure out which dependencies
   only need to have bitcode in them. Pure-bitcode artifacts are emitted
   with the `-Clinker-plugin-lto` flag. Some artifacts are still used in
   multiple scenarios (such as those shared between build scripts and final
   artifacts), so those are not compiled with `-Clinker-plugin-lto` since
   the linker is not guaranteed to know how to perform LTO.
   
   This functionality was recently implemented in rust-lang/rust#71528
   where rustc is now capable of reading bitcode from `-Clinker-plugin-lto`
   rlibs. Previously rustc would only read its own format of bitcode, but
   this has now been extended! This support is now on nightly, hence this
   PR.

   

   alexcrichton committed May 4, 2020
   Configuration menu

   • View commit details
   • Copy full SHA for e221925
   • Browse repository at this point

   Copy the full SHA

   e221925 View commit details

   Browse the repository at this point in the history