#8668: SPECIALIZE silently fails to apply
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Reporter: crockeea | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.8.3
Resolution: | Keywords: Inlining
Operating System: Unknown/Multiple | Architecture: x86_64
Type of failure: Runtime | (amd64)
performance bug | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by nfrisby):
Executive summary: It looks like the expected optimization is achieved in
GHC 7.10.2. I don't know if something was broken and is now fixed or if
some other change side-stepped the original problem, etc. etc.
In GHC 7.10.2, `fcTest` seems to be ''faster'' than `vtTest` (5
repetitions, using the same `-O3` setting that crockeea used); that's a
reversal of the originally discussed behavior.
Compiling `Foo.hs` yields the following rule, which fires when compiling
`Main.hs`, in spite of the dfuns on the LHS (see #7080).
{{{
------ Local rules for imported ids --------
"SPEC plusFastCyc" [ALWAYS]
forall (@ m_a3Ai)
($dFactored_a3Aj :: Factored m_a3Ai Int)
($dVector_a3Bz :: V.Vector U.Vector Int).
plusFastCyc @ (VT U.Vector m_a3Ai)
@ Int
(Foo.$fNumVT
@ U.Vector
@ m_a3Ai
@ Int
(GHC.Real.$p1Real
@ Int
(GHC.Real.$p1Integral
@ Int
($dFactored_a3Aj
`cast` (Foo.NTCo:Factored[0]