#14152: Float exit paths out of recursive functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: JoinPoints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #14137 #10918 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nomeata): Note to myself: == Common up identical exit paths I expect much code to look like this: {{{ let x = f x0 joinrec go 0 = h x go 10 = h x go 30 = if something then h x else call go (n-1) go 40 = if something then h (x+1) else call go (n-1) go n = call go (n-1) in call go 10 }}} where a recursive function checks a bunch of conditions and has the same exit code multiple times. Ih would be silly to create three joint points with `h x` as the right hand side. So when floating out these exit expressions, I plan to check if the same expression is already being floated out and use that join point, to get {{{ let x = f x0 join exit1 = h x join exit2 = h (x+1) joinrec go 0 = call exit1 go 10 = call exit1 go 30 = if something then call exit1 else call go (n-1) go 40 = if something then call exit2 else call go (n-1) go n = call go (n-1) in call go 10 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14152#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler