#2465: View + Pattern Match not fused sufficiently
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Reporter: ryani | Owner:
Type: compile-time performance bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.2
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: x86
Os: Windows |
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Comment (by ryani):
Also, to answer your question directly... what in the core should be
different?
The list thunk allocations in
[http://hackage.haskell.org/trac/ghc/attachment/ticket/2465/plzoptimize.core#L490
$sdnaView (line 490)] and
[http://hackage.haskell.org/trac/ghc/attachment/ticket/2465/plzoptimize.core#L521
dnaView (line 521)] immediately get destructed by
[http://hackage.haskell.org/trac/ghc/attachment/ticket/2465/plzoptimize.core#L386
$wconsts (line 386)], causing a lot of allocator churn.
If those two functions are fused, as they are in optConsts, the code runs
~5-10x faster (from my recollection).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2465#comment:4>
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