#8731: long compilation time for module with large data type and partial record selectors -------------------------+------------------------------------------------- Reporter: | Owner: carter | Status: new Type: bug | Milestone: Priority: | Version: 7.8.1-rc1 normal | Operating System: Unknown/Multiple Component: | Type of failure: Compile-time performance bug Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- in both ghc 7.6 and 7.8rc, the Constants module in LLVM-General-Pure (and a few other similar modules) have surprisingly long (and noticable!) compilation times. This seems to related to how GHC handles a many constructor data type with overlapping field names. the time is nearly the same for building a static module with O1 and O2 {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O2 1 ↵ [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O2 7.52s user 0.23s system 99% cpu 7.755 total }}} {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O1 [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O1 6.62s user 0.20s system 100% cpu 6.768 total }}} heck even with -O0 its slow (though not terrible) {{{ carter repoScratcher/bad-ast » time ghc Constant.hs -O0 [1 of 1] Compiling Constant ( Constant.hs, Constant.o ) ghc Constant.hs -O0 2.76s user 0.14s system 101% cpu 2.873 total }}} Seems like there might something wrong in how we handle data types like this, the complexity need not -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8731 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler