#10694: CPR analysis too optimistic when returning a component of a product -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: 10678 Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by rwbarton): To demonstrate the problem, if I build with `-funfolding-use-threshold=1` to induce w/w to run, I get this core (with `-dsuppress-all`): {{{ -- RHS size: {terms: 11, types: 9, coercions: 0} $wm $wm = \ w_sDP w1_sDQ -> case pm w_sDP w1_sDQ of _ { (pr_as8, mr_as9) -> case mr_as9 of _ { I# ww1_sDT -> ww1_sDT } } -- RHS size: {terms: 9, types: 3, coercions: 0} m m = \ w_sDP w1_sDQ -> case $wm w_sDP w1_sDQ of ww_sDT { __DEFAULT -> I# ww_sDT } }}} This can only lose, never gain, compared to not generating a worker/wrapper pair. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10694#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler