#14737: Improve performance of Simplify.simplCast -------------------------------------+------------------------------------- Reporter: tdammers | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #11735 #14683 | Differential Rev(s): Phab:D4385 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Try getting rid of the first equation for `puchCoTyArg` {{{ pushCoTyArg co ty | tyL `eqType` tyR = Just (ty, mkRepReflCo (piResultTy tyR ty)) }}} This is another big pile of type-equalities, rather like calling `isReflexiveCo` at the wrong moment. Claim: if it happens that `tyL` = `tyR`, but we go ahead with all that `mkCoherenceLeftCo` stuff anyway, then the coercion optimiser will get rid of it later. '''Richard''': will it? But try that change anyway. NO WAY should `pushCoTyArg` take 54% of compile time! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14737#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler