#4936: Unbox sum types without fields
---------------------------------+------------------------------------------
Reporter: tibbe | Owner:
Type: feature request | Status: new
Priority: normal | Component: Compiler
Version: 7.0.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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In the new I/O manager we use newtyped `Int`s instead of an ADT to squeeze
out every drop of performance GHC can give us. It's a bit unfortunate that
we have to make a choice between performance and safety here. Using an ADT
have many benefits. For example, all possible values are grouped together
neatly under the data type and the compiler can make sure we check all
possible cases in case statements.
Pointer tagging helps quite a bit here, if you have fewer than 4 (or 8)
constructors. If you have more you don't get the benefit.
Given a simple sum type like this:
{{{
data Color = Red | Green | Blue | Yellow
}}}
change its representation to an `Int`, allowing it to be unboxed into data
types.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4936>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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