• Simon Marlow's avatar
    Rollback INLINE patches · e79c9ce0
    Simon Marlow authored
    rolling back:
    
    Fri Dec  5 16:54:00 GMT 2008  simonpj@microsoft.com
      * Completely new treatment of INLINE pragmas (big patch)
      
      This is a major patch, which changes the way INLINE pragmas work.
      Although lots of files are touched, the net is only +21 lines of
      code -- and I bet that most of those are comments!
      
      HEADS UP: interface file format has changed, so you'll need to
      recompile everything.
      
      There is not much effect on overall performance for nofib, 
      probably because those programs don't make heavy use of INLINE pragmas.
      
              Program           Size    Allocs   Runtime   Elapsed
                  Min         -11.3%     -6.9%     -9.2%     -8.2%
                  Max          -0.1%     +4.6%     +7.5%     +8.9%
       Geometric Mean          -2.2%     -0.2%     -1.0%     -0.8%
      
      (The +4.6% for on allocs is cichelli; see other patch relating to
      -fpass-case-bndr-to-join-points.)
      
      The old INLINE system
      ~~~~~~~~~~~~~~~~~~~~~
      The old system worked like this. A function with an INLINE pragam
      got a right-hand side which looked like
           f = __inline_me__ (\xy. e)
      The __inline_me__ part was an InlineNote, and was treated specially
      in various ways.  Notably, the simplifier didn't inline inside an
      __inline_me__ note.  
      
      As a result, the code for f itself was pretty crappy. That matters
      if you say (map f xs), because then you execute the code for f,
      rather than inlining a copy at the call site.
      
      The new story: InlineRules
      ~~~~~~~~~~~~~~~~~~~~~~~~~~
      The new system removes the InlineMe Note altogether.  Instead there
      is a new constructor InlineRule in CoreSyn.Unfolding.  This is a 
      bit like a RULE, in that it remembers the template to be inlined inside
      the InlineRule.  No simplification or inlining is done on an InlineRule,
      just like RULEs.  
      
      An Id can have an InlineRule *or* a CoreUnfolding (since these are two
      constructors from Unfolding). The simplifier treats them differently:
      
        - An InlineRule is has the substitution applied (like RULES) but 
          is otherwise left undisturbed.
      
        - A CoreUnfolding is updated with the new RHS of the definition,
          on each iteration of the simplifier.
      
      An InlineRule fires regardless of size, but *only* when the function
      is applied to enough arguments.  The "arity" of the rule is specified
      (by the programmer) as the number of args on the LHS of the "=".  So
      it makes a difference whether you say
        	{-# INLINE f #-}
      	f x = \y -> e     or     f x y = e
      This is one of the big new features that InlineRule gives us, and it
      is one that Roman really wanted.
      
      In contrast, a CoreUnfolding can fire when it is applied to fewer
      args than than the function has lambdas, provided the result is small
      enough.
      
      
      Consequential stuff
      ~~~~~~~~~~~~~~~~~~~
      * A 'wrapper' no longer has a WrapperInfo in the IdInfo.  Instead,
        the InlineRule has a field identifying wrappers.
      
      * Of course, IfaceSyn and interface serialisation changes appropriately.
      
      * Making implication constraints inline nicely was a bit fiddly. In
        the end I added a var_inline field to HsBInd.VarBind, which is why
        this patch affects the type checker slightly
      
      * I made some changes to the way in which eta expansion happens in
        CorePrep, mainly to ensure that *arguments* that become let-bound
        are also eta-expanded.  I'm still not too happy with the clarity
        and robustness fo the result.
      
      * We now complain if the programmer gives an INLINE pragma for
        a recursive function (prevsiously we just ignored it).  Reason for
        change: we don't want an InlineRule on a LoopBreaker, because then
        we'd have to check for loop-breaker-hood at occurrence sites (which
        isn't currenlty done).  Some tests need changing as a result.
      
      This patch has been in my tree for quite a while, so there are
      probably some other minor changes.
      
    
        M ./compiler/basicTypes/Id.lhs -11
        M ./compiler/basicTypes/IdInfo.lhs -82
        M ./compiler/basicTypes/MkId.lhs -2 +2
        M ./compiler/coreSyn/CoreFVs.lhs -2 +25
        M ./compiler/coreSyn/CoreLint.lhs -5 +1
        M ./compiler/coreSyn/CorePrep.lhs -59 +53
        M ./compiler/coreSyn/CoreSubst.lhs -22 +31
        M ./compiler/coreSyn/CoreSyn.lhs -66 +92
        M ./compiler/coreSyn/CoreUnfold.lhs -112 +112
        M ./compiler/coreSyn/CoreUtils.lhs -185 +184
        M ./compiler/coreSyn/MkExternalCore.lhs -1
        M ./compiler/coreSyn/PprCore.lhs -4 +40
        M ./compiler/deSugar/DsBinds.lhs -70 +118
        M ./compiler/deSugar/DsForeign.lhs -2 +4
        M ./compiler/deSugar/DsMeta.hs -4 +3
        M ./compiler/hsSyn/HsBinds.lhs -3 +3
        M ./compiler/hsSyn/HsUtils.lhs -2 +7
        M ./compiler/iface/BinIface.hs -11 +25
        M ./compiler/iface/IfaceSyn.lhs -13 +21
        M ./compiler/iface/MkIface.lhs -24 +19
        M ./compiler/iface/TcIface.lhs -29 +23
        M ./compiler/main/TidyPgm.lhs -55 +49
        M ./compiler/parser/ParserCore.y -5 +6
        M ./compiler/simplCore/CSE.lhs -2 +1
        M ./compiler/simplCore/FloatIn.lhs -6 +1
        M ./compiler/simplCore/FloatOut.lhs -23
        M ./compiler/simplCore/OccurAnal.lhs -36 +5
        M ./compiler/simplCore/SetLevels.lhs -59 +54
        M ./compiler/simplCore/SimplCore.lhs -48 +52
        M ./compiler/simplCore/SimplEnv.lhs -26 +22
        M ./compiler/simplCore/SimplUtils.lhs -28 +4
        M ./compiler/simplCore/Simplify.lhs -91 +109
        M ./compiler/specialise/Specialise.lhs -15 +18
        M ./compiler/stranal/WorkWrap.lhs -14 +11
        M ./compiler/stranal/WwLib.lhs -2 +2
        M ./compiler/typecheck/Inst.lhs -1 +3
        M ./compiler/typecheck/TcBinds.lhs -17 +27
        M ./compiler/typecheck/TcClassDcl.lhs -1 +2
        M ./compiler/typecheck/TcExpr.lhs -4 +6
        M ./compiler/typecheck/TcForeign.lhs -1 +1
        M ./compiler/typecheck/TcGenDeriv.lhs -14 +13
        M ./compiler/typecheck/TcHsSyn.lhs -3 +2
        M ./compiler/typecheck/TcInstDcls.lhs -5 +4
        M ./compiler/typecheck/TcRnDriver.lhs -2 +11
        M ./compiler/typecheck/TcSimplify.lhs -10 +17
        M ./compiler/vectorise/VectType.hs +7
    
    Mon Dec  8 12:43:10 GMT 2008  simonpj@microsoft.com
      * White space only
    
        M ./compiler/simplCore/Simplify.lhs -2
    
    Mon Dec  8 12:48:40 GMT 2008  simonpj@microsoft.com
      * Move simpleOptExpr from CoreUnfold to CoreSubst
    
        M ./compiler/coreSyn/CoreSubst.lhs -1 +87
        M ./compiler/coreSyn/CoreUnfold.lhs -72 +1
    
    Mon Dec  8 17:30:18 GMT 2008  simonpj@microsoft.com
      * Use CoreSubst.simpleOptExpr in place of the ad-hoc simpleSubst (reduces code too)
    
        M ./compiler/deSugar/DsBinds.lhs -50 +16
    
    Tue Dec  9 17:03:02 GMT 2008  simonpj@microsoft.com
      * Fix Trac #2861: bogus eta expansion
      
      Urghlhl!  I "tided up" the treatment of the "state hack" in CoreUtils, but
      missed an unexpected interaction with the way that a bottoming function
      simply swallows excess arguments.  There's a long
           Note [State hack and bottoming functions]
      to explain (which accounts for most of the new lines of code).
      
    
        M ./compiler/coreSyn/CoreUtils.lhs -16 +53
    
    Mon Dec 15 10:02:21 GMT 2008  Simon Marlow <marlowsd@gmail.com>
      * Revert CorePrep part of "Completely new treatment of INLINE pragmas..."
      
      The original patch said:
      
      * I made some changes to the way in which eta expansion happens in
        CorePrep, mainly to ensure that *arguments* that become let-bound
        are also eta-expanded.  I'm still not too happy with the clarity
        and robustness fo the result.
        
      Unfortunately this change apparently broke some invariants that were
      relied on elsewhere, and in particular lead to panics when compiling
      with profiling on.
      
      Will re-investigate in the new year.
    
        M ./compiler/coreSyn/CorePrep.lhs -53 +58
        M ./configure.ac -1 +1
    
    Mon Dec 15 12:28:51 GMT 2008  Simon Marlow <marlowsd@gmail.com>
      * revert accidental change to configure.ac
    
        M ./configure.ac -1 +1
    e79c9ce0
CoreFVs.lhs 15.7 KB