#5658: Strict bindings are wrongly floated out of case alternatives.
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Reporter: benl | Owner: benl
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.2.1
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Runtime crash
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Changes (by simonmar):
* difficulty: => Unknown
Comment:
I think of `has_side_effects` as implying `can_fail`, but not vice versa.
* A primop that is neither `can_fail` nor `has_side_effects` can be
executed speculatively, any number of times
* A primop that is marked `can_fail` cannot be executed speculatively,
but it can be repeated (why would you want to do that? Perhaps it might
enable some eta-expansion, if you can prove that the lambda is definitely
applied at least once. I guess we don't currently do that).
* A primop that is marked `has_side_effects` can be neither speculated
nor repeated; it must be executed exactly the right number of times.
This is all moot since as you point out we don't currently take advantage
of `can_fail && !has_side_effects`.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5658#comment:6>
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