#5780: -faggressive-primops change caused a failure in perf/compiler/parsing001
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Reporter: simonmar | Owner:
Type: bug | Status: new
Priority: high | Milestone: 7.6.1
Component: Compiler | Version: 7.2.2
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by simonpj):
BTW here's the original commit message (the one that was reverted):
{{{
commit 601c983dd0bada6b49bdadd8f172fd4eacac4b0c
Author: Simon Peyton Jones <[email protected]>
Date: Fri Jan 13 17:50:00 2012 +0000
Add -faggressive-primops plus refactoring in CoreUtils
I'm experimenting with making GHC a bit more aggressive about
a) dropping case expressions if the result is unused
Simplify.rebuildCase, CaseElim equation
b) floating case expressions inwards
FloatIn.fiExpr, AnnCase
In both cases the new behaviour is gotten with a static (debug)
flag -faggressive-primops. The extra "aggression" is to allow
discarding and floating in for side-effecting operations. See
the new, extensive Note [PrimOp can_fail and has_side_effects]
in PrimoOp.
When discarding a case with unused binders, in the lifted-type
case it's definitely ok if the scrutinee terminates; previously
we were checking exprOkForSpeculation, which is significantly
worse.
So I wanted a new function CoreUtils.exprCertainlyTerminates.
In doing this I ended up with a significant refactoring in
CoreUtils. The new structure has quite a lot of nice sharing:
exprIsCheap = exprIsCheap' isHNFApp
exprIsExpandable = exprIsCheap' isConLikeApp
exprIsHNF = exprIsHNFlike isHNFApp
exprIsConLike = exprIsHNFlike isConLikeApp
exprCertainlyTerminates = exprIsHNFlike isTerminatingApp
compiler/coreSyn/CoreArity.lhs | 4 +-
compiler/coreSyn/CoreUtils.lhs | 237
++++++++++++++++++++----------------
compiler/main/StaticFlagParser.hs | 1 +
compiler/main/StaticFlags.hs | 6 +
compiler/prelude/PrimOp.lhs | 59 +++++++--
compiler/simplCore/FloatIn.lhs | 10 ++-
compiler/simplCore/OccurAnal.lhs | 4 +-
compiler/simplCore/SimplUtils.lhs | 10 +-
compiler/simplCore/Simplify.lhs | 20 ++--
9 files changed, 214 insertions(+), 137 deletions(-)
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5780#comment:2>
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