[GHC] #13156: CSE missing an easy case
GHC
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Fri Jan 20 11:37:50 UTC 2017
#13156: CSE missing an easy case
-------------------------------------+-------------------------------------
Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 8.2.1
Component: Compiler | Version: 8.0.1
Keywords: | Operating System: Unknown/Multiple
Architecture: | Type of failure: None/Unknown
Unknown/Multiple |
Test Case: | Blocked By:
Blocking: | Related Tickets:
Differential Rev(s): | Wiki Page:
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Consider this Core:
{{{
case f @Int of { r1 ->
case f @Int of { r2 -> ...
}}}
There is an easy common sub-expression to be had here, which would allow
to eliminate a case expression, but CSE didn't spot it in GHC 8.
Easy to fix. Here's an example that shows it
{{{
module Bug where
f g x = let r :: [a] -> [a]
r = case g x of True -> reverse . reverse
False -> reverse
in
r `seq` r `seq` True
}}}
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13156>
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