#10137: Rewrite switch code generation -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 (CodeGen) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #9157, #8326, | Differential Revisions: #8317, #9159 | -------------------------------------+------------------------------------- Comment (by nomeata):
Note that when matching on an enumeration type, we can assume that the constructor tag is within the range of possible tag values. We cannot make any such assumption for matches on ints. So, we should remember the extra information that we have about the range when doing this reduction.
Right. The datatype is currently {{{ data SwitchTargets = SwitchTargets (Maybe (Integer, Integer)) (Maybe Label) (M.Map Integer Label) }}} so there optionally is a definite range (absent when matching literal). The function `addRange` in the new `CmmSwitch` module (currently in branch `wip/T10137`) takes care of that case, before the general layout algorithm runs on the remaining range. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10137#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler