[GHC] #5598: Function quotRem is inefficient

[GHC]

#5598: Function quotRem is inefficient
---------------------------------+------------------------------------------
    Reporter:  boris             |       Owner:                               
        Type:  task              |      Status:  new                          
    Priority:  normal            |   Component:  Compiler                     
     Version:  7.0.3             |    Keywords:  division, performance, primop
    Testcase:                    |   Blockedby:                               
          Os:  Unknown/Multiple  |    Blocking:                               
Architecture:  x86               |     Failure:  Runtime performance bug      
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 Function quotRem gets compiled into two div instructions although div
 computes both quotient and remainder. This inefficiency exists both with
 NCG and LLVM backends. Thus, quotRem is at least twice as slow as it could
 be.

 As far as I understand, quotRem is decomposed into two primops quotInt#
 and remInt# (or quotWord# and remWord#) and each of them is compiled
 independently into code which has div instruction. I propose to add new
 primops quotRemInt# and quotRemWord# to address this flaw.

 Please see the sample code and corresponding assembly.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5598>
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