#14186: CSE fails to CSE two identical large top-level functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Ha ha. This is caused by two things 1. We don't CSE things with an INLINE pragma: see `Note [CSE for INLINE and NOINLINE]` in `CSE.hs` 2. The worker/wrapper pass (right after demand analysis) gives the wrapper an inline pragma of `INLINE[0]`. So (2) means that (1) means no CSE for `foo` and `bar`. Sigh. What to do? Well * `InlinePragma` already distinguishse between the `inl_inline` field and `inl_act`. See `Note [inl_inline and inl_act]` in `BasicTypes`. * So we should be able to distinguish between a user-supplied INLINE pragma `inl_inline` and one supplied the w/w pass. * If we could distinguish then CSDE could fail on the user-supplied kind, but succeed on the w/w supplied kind. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14186#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#14186: CSE fails to CSE two identical large top-level functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): I think perhaps the `wrap_prag` can be `EmptyInlineSpec`. That might do it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14186#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#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

#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: | -------------------------------------+------------------------------------- Comment (by Joachim Breitner ): In [changeset:"fe35b85a8cc72582e0f98a3059be00a9a2318a4a/ghc" fe35b85a/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="fe35b85a8cc72582e0f98a3059be00a9a2318a4a" Add testcase for #14186 and move the generally useful helpers check_errmsg and grep_errmsg to testlib.py. Some documentation can be found on https://ghc.haskell.org/trac/ghc/wiki/Building/RunningTests/Adding }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14186#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler