#14186: CSE fails to CSE two identical large top-level functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.3 Resolution: | Keywords: CSE Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13589 | Differential Rev(s): Phab:D3939 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * keywords: => CSE * related: => #13589 Old description:
Consider this code:
{{{ module CSEBug where
data Succs a = Succs a [a]
instance Functor Succs where fmap f (Succs o s) = Succs (f o) (map f s)
foo, bar :: (a -> b) -> (b -> c) -> Succs a -> Succs c foo f g x = fmap (g . f) x bar f g x = fmap (g . f) x }}}
If I compile this with `-O`, `foo` and `bar` are not CSEd, which can be seen with `-ddump-cse`.
Removing either the first or the second argument of `Succs` makes CSE work.
Is there a size limit on CSE?
New description: Consider this code: {{{#!hs module CSEBug where data Succs a = Succs a [a] instance Functor Succs where fmap f (Succs o s) = Succs (f o) (map f s) foo, bar :: (a -> b) -> (b -> c) -> Succs a -> Succs c foo f g x = fmap (g . f) x bar f g x = fmap (g . f) x }}} If I compile this with `-O`, `foo` and `bar` are not CSEd, which can be seen with `-ddump-cse`. Removing either the first or the second argument of `Succs` makes CSE work. Is there a size limit on CSE? -- Comment: #131589 is also somewhat relevant here. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14186#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler