#7960: Compiling profiling CCS registration .c file takes far too long -----------------------------------------+---------------------------------- Reporter: duncan | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Compile-time performance bug | Blockedby: Blocking: | Related: -----------------------------------------+---------------------------------- When compiling executables for profiling, ghc generates a .c file something like this: {{{ #define IN_STG_CODE 0 #include "Rts.h" #include "Stg.h" static void prof_init_Main(void) __attribute__((constructor)); static void prof_init_Main(void) {extern CostCentre Foo_bar_cc[]; REGISTER_CC(Foo_bar_cc); ... }}} When there are a large number of CCSs, e.g. 10's of 1,000s (as can easily happen with large projects and using `-fprof-auto`) then of course this .c file and this single C function become very large. The C compiler then takes a very long time to compile it. For example, with a .c file with ~27k lines (so about half that number of CCSs), gcc 4.7.2 with -O1 takes about 20 minutes to compile. With -O0 it takes about 4 seconds. Clearly this version of gcc does not cope very well with this massive function at -O1 level. I suggest that since the initialisation is not performance critical, and it doesn't look like there is a lot to optimise here anyway, that ghc compile this .c file without passing gcc the -O flag. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7960 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler