Re: [GHC] #8900: Strictness analysis regression

#8900: Strictness analysis regression --------------------------------------------+------------------------------ Reporter: tibbe | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.1-rc2 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 Type of failure: Runtime performance bug | (amd64) Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Comment (by Simon Peyton Jones ): In [changeset:"0b6fa3e95078797f87302780a85607decab806fb/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="0b6fa3e95078797f87302780a85607decab806fb" Eliminate redundant seq's (Trac #8900) This patch makes the simplifier eliminate a redundant seq like case x of y -> ...y.... where y is used strictly. GHC used to do this, but I made it less aggressive in commit 28d9a03253e8fd613667526a170b684f2017d299 (Jan 2013) However #8900 shows that doing so sometimes loses good transformations; and the transformation is valid according to "A semantics for imprecise exceptions". So I'm restoring the old behaviour. See Note [Eliminating redundant seqs] }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8900#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler