#9238: Negative zero broken -------------------------------------+------------------------------------- Reporter: augustss | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Incorrect | Blocked By: result at runtime | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by rwbarton): When we do {{{ case ds1 of wild_XT { -- ds1 :: Double# (y = D# ds1) __DEFAULT -> ... 0.0 -> ... } }}} inside the `0.0` case we seem to create a local unfolding `ds1 = 0.0`. You can see this happening with `-dverbose-core2core -ddump-inlinings`: search for "Inlining done: x" or "ds1". This is wrong because the `0.0` case matches both positive and negative zero. That is the correct semantics that makes the Core match the original program, and it is implemented correctly by the code generation. But it means that we can't create this local unfolding when the pattern is specifically `0.0`. I don't know where this unfolding gets created, or I'd try to fix it myself. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9238#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler