#9142: LLVM HEAD rejects aliases used by LLVM codegen -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 7.10.1 Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Differential Revisions: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: 4213 Blocked By: | Related Tickets: | -------------------------------------+------------------------------------- Comment (by bgamari): This morning I approached this issue with a fresh perspective and realized that the solutions is quite simple (unless I've missed something). The issue with new LLVMs is that aliases can't point to things that aren't definitions. As it turns out, the only case where we emit aliases pointing to non- definitions is for external symbols where we emit an extern declaration and a corresponding alias. Unless I'm mistaken, there is no reason why both of these are necessary: we only use the alias. So, instead of emitting, {{{ @stg_BCO_info = external global i8 @stg_BCO_info$alias = alias private i8* @stg_BCO_info }}} we should be emitting, {{{ @stg_BCO_info$alias = external global i8 }}} I've implemented this change in my [llvm-3.5-new branch https://github.com/bgamari/ghc/compare/llvm-3.5-new and it appears to work (or rather, the GHC build hasn't failed yet; I also have yet to verify that LLVM 3.4 still works). Of course, there are still nice opportunities for cleaning up TNTC (as discussed in #4213), but at least this fixes the immediate problem. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9142#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler