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| author | Andreas Klebinger <klebinger.andreas@gmx.at> | 2022-11-17 16:08:40 +0100 |
|---|---|---|
| committer | Andreas Klebinger <klebinger.andreas@gmx.at> | 2022-11-21 14:37:54 +0100 |
| commit | ce608479c7f40a9899a6448379d05861bee77b41 (patch) | |
| tree | 156d926831625eaaaab86f7c291aa9e74c9a5ca2 | |
| parent | 74ca6191fa0dbbe8cee3dc53741b8d59fbf16b09 (diff) | |
| download | haskell-wip/andreask/92-dlist.tar.gz | |
Fix #22425 - Broken eta-expansion over expensive work.wip/andreask/92-dlist
This is the 9.2 backport of !9357
Through a mistake in the latest backport we started eta-expanding over
expensive work by mistake. E.g. over <expensive> in code like:
case x of
A -> id
B -> <expensive>
We fix this by only eta-expanding over <expensive> if all other branches
are headed by an oneShot lambda.
In the long story of broken eta-expansion on 9.2/9.4 this is hopefully
the last chapter.
-------------------------
Metric Increase:
CoOpt_Read
T1969
parsing001
TcPlugin_RewritePerf
LargeRecord
-------------------------
| -rw-r--r-- | compiler/GHC/Core/Opt/Arity.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs index 1c6f9bed8b..66af0586f3 100644 --- a/compiler/GHC/Core/Opt/Arity.hs +++ b/compiler/GHC/Core/Opt/Arity.hs @@ -791,7 +791,7 @@ andArityType env (AT [] div1) at2 = andWithTail env div1 at2 andArityType env at1 (AT [] div2) = andWithTail env div2 at1 andWithTail :: ArityEnv -> Divergence -> ArityType -> ArityType -andWithTail env div1 at2@(AT lams2 _) +andWithTail env div1 at2 | isDeadEndDiv div1 -- case x of { T -> error; F -> \y.e } = at2 -- Note [ABot branches: max arity wins] @@ -799,7 +799,7 @@ andWithTail env div1 at2@(AT lams2 _) = AT [] topDiv | otherwise -- case x of { T -> plusInt <expensive>; F -> \y.e } - = AT lams2 topDiv -- We know div1 = topDiv + = takeWhileOneShot at2 -- We know div1 = topDiv -- See Note [Combining case branches: andWithTail] |