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  • #11533
Closed
Open
Created Feb 03, 2016 by jscholl@trac-jscholl

Stack check not optimized out even if it could be

CmmLayoutStack tries to remove a stack check if a function uses no stack space. It knows that Sp < SpLim is always false, but not that Sp >= SpLim is always true. However, the latter can arise when GHC flips the comparison (which it does sometimes).

An example would be the worker function generated for go:

countDown :: Int -> Int
countDown = go 0
    where
        go acc n | n > 0 = go (acc + 1) (n - 1)
                 | otherwise = acc + n
Trac metadata
Trac field Value
Version 7.10.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (CodeGen)
Test case
Differential revisions
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