#7258: Compiling DynFlags is jolly slow -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: deriving-perf Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
the t-10-XXXX examples are maybe too small to produce useful metrics,
I wasn't measuring performance; I was just eye-balling the (identical) code.
The profiler breakdown looks radically different between the optimized and unoptimized versions, for *all* examples
OK, so there are two perhaps-different problems * With -O compiling `DynFlags` is jolly slow. (The original bug report.) * Without -O we get non-linear stuff going on (comment:43) I think the -O case is the higher-priority item. (Though I accept that compiling without -O is supposed to be fast.) I would stick to -O for now, not -O2. The latter involves `SpecConstr` and `LiberateCase` both of which can generate a lot of code. Again let's not ignore -O2 but let's nail -O first. So what do the -O graphs look like? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7258#comment:52 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler