However, if the binding can go all the way to the top level, then there seems no downside to floating it: we end up with a smaller (and hence
#15560: Full laziness destroys opportunities for join points -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 (CodeGen) | Resolution: | Keywords: JoinPoints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #14287 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by AndreasK): perhaps more inlinable) function; and the jump to the join point is still a nice, efficient jump. What's not to like? There are no top level join points as far as I know. (I might be mistaken though?) Turning them into a top level binding means the calling convention changes into the same that is used with regular functions. So we have the overhead of register saving, stack checks, layout penalty, the works. Limiting them to the top of the RHS instead seems like an advantage. Maybe that should already happen and I just hit a bug there? I haven't looked too far into the SetLevel machinery. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15560#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler