Commits on Apr 29, 2020

1. Store LLVM bitcode in object files, not compressed …

   This commit is an attempted resurrection of rust-lang#70458 where LLVM bitcode
   emitted by rustc into rlibs is stored into object file sections rather
   than in a separate file. The main rationale for doing this is that when
   rustc emits bitcode it will no longer use a custom compression scheme
   which makes it both easier to interoperate with existing tools and also
   cuts down on compile time since this compression isn't happening.
   
   The blocker for this in rust-lang#70458 turned out to be that native linkers
   didn't handle the new sections well, causing the sections to either
   trigger bugs in the linker or actually end up in the final linked
   artifact. This commit attempts to address these issues by ensuring that
   native linkers ignore the new sections by inserting custom flags with
   module-level inline assembly.
   
   Note that this does not currently change the API of the compiler at all.
   The pre-existing `-C bitcode-in-rlib` flag is co-opted to indicate
   whether the bitcode should be present in the object file or not.
   
   Finally, note that an important consequence of this commit, which is also
   one of its primary purposes, is to enable rustc's `-Clto` bitcode
   loading to load rlibs produced with `-Clinker-plugin-lto`. The goal here
   is that when you're building with LTO Cargo will tell rustc to skip
   codegen of all intermediate crates and only generate LLVM IR. Today
   rustc will generate both object code and LLVM IR, but the object code is
   later simply thrown away, wastefully.

   

   alexcrichton committed Apr 29, 2020
   Configuration menu

   • View commit details
   • Copy full SHA for ef89cc8
   • Browse repository at this point

   Copy the full SHA

   ef89cc8 View commit details

   Browse the repository at this point in the history