Commit 07160d61 authored by simonpj@microsoft.com's avatar simonpj@microsoft.com
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parent 32722dc3
......@@ -474,7 +474,22 @@ The thunk_cpr_ok stuff [CPR-AND-STRICTNESS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the rhs is a thunk, we usually forget the CPR info, because
it is presumably shared (else it would have been inlined, and
so we'd lose sharing if w/w'd it into a function.
so we'd lose sharing if w/w'd it into a function). E.g.
let r = case expensive of
(a,b) -> (b,a)
in ...
If we marked r as having the CPR property, then we'd w/w into
let $wr = \() -> case expensive of
(a,b) -> (# b, a #)
r = case $wr () of
(# b,a #) -> (b,a)
in ...
But now r is a thunk, which won't be inlined, so we are no further ahead.
However, if the strictness analyser has figured out (in a previous
iteration) that it's strict, then we DON'T need to forget the CPR info.
......
......@@ -317,7 +317,7 @@ splitThunk transforms like this:
Now simplifier will transform to
case x-rhs of
I# a -> let x* = I# b
I# a -> let x* = I# a
in body
which is what we want. Now suppose x-rhs is itself a case:
......
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