1. 12 Jan, 2011 1 commit
    • simonpj@microsoft.com's avatar
      Major refactoring of the type inference engine · 27310213
      simonpj@microsoft.com authored
      This patch embodies many, many changes to the contraint solver, which
      make it simpler, more robust, and more beautiful.  But it has taken
      me ages to get right. The forcing issue was some obscure programs
      involving recursive dictionaries, but these eventually led to a
      massive refactoring sweep.
      
      Main changes are:
       * No more "frozen errors" in the monad.  Instead "insoluble
         constraints" are now part of the WantedConstraints type.
      
       * The WantedConstraint type is a product of bags, instead of (as
         before) a bag of sums.  This eliminates a good deal of tagging and
         untagging.
      
       * This same WantedConstraints data type is used
           - As the way that constraints are gathered
           - As a field of an implication constraint
           - As both argument and result of solveWanted
           - As the argument to reportUnsolved
      
       * We do not generate any evidence for Derived constraints. They are
         purely there to allow "impovement" by unifying unification
         variables.
      
       * In consequence, nothing is ever *rewritten* by a Derived
         constraint.  This removes, by construction, all the horrible
         potential recursive-dictionary loops that were making us tear our
         hair out.  No more isGoodRecEv search either. Hurrah!
      
       * We add the superclass Derived constraints during canonicalisation,
         after checking for duplicates.  So fewer superclass constraints
         are generated than before.
      
       * Skolem tc-tyvars no longer carry SkolemInfo.  Instead, the
         SkolemInfo lives in the GivenLoc of the Implication, where it
         can be tidied, zonked, and substituted nicely.  This alone is
         a major improvement.
      
       * Tidying is improved, so that we tend to get t1, t2, t3, rather
         than t1, t11, t111, etc
      
         Moreover, unification variables are always printed with a digit
         (thus a0, a1, etc), so that plain 'a' is available for a skolem
         arising from a type signature etc. In this way,
           (a) We quietly say which variables are unification variables,
               for those who know and care
           (b) Types tend to get printed as the user expects.  If he writes
                   f :: a -> a
                   f = ...blah...
               then types involving 'a' get printed with 'a', rather than
               some tidied variant.
      
       * There are significant improvements in error messages, notably
         in the "Cannot deduce X from Y" messages.
      27310213
  2. 13 Dec, 2010 1 commit
    • simonpj@microsoft.com's avatar
      Fix recursive superclasses (again). Fixes Trac #4809. · a3bab050
      simonpj@microsoft.com authored
      This patch finally deals with the super-delicate question of
      superclases in possibly-recursive dictionaries.  The key idea
      is the DFun Superclass Invariant (see TcInstDcls):
      
           In the body of a DFun, every superclass argument to the
           returned dictionary is
             either   * one of the arguments of the DFun,
             or       * constant, bound at top level
      
      To establish the invariant, we add new "silent" superclass
      argument(s) to each dfun, so that the dfun does not do superclass
      selection internally.  There's a bit of hoo-ha to make sure that
      we don't print those silent arguments in error messages; a knock
      on effect was a change in interface-file format.
      
      A second change is that instead of the complex and fragile
      "self dictionary binding" in TcInstDcls and TcClassDcl,
      using the same mechanism for existential pattern bindings.
      See Note [Subtle interaction of recursion and overlap] in TcInstDcls
      and Note [Binding when looking up instances] in InstEnv.
      
      Main notes are here:
      
        * Note [Silent Superclass Arguments] in TcInstDcls,
          including the DFun Superclass Invariant
      
      Main code changes are:
      
        * The code for MkId.mkDictFunId and mkDictFunTy
      
        * DFunUnfoldings get a little more complicated;
          their arguments are a new type DFunArg (in CoreSyn)
      
        * No "self" argument in tcInstanceMethod
        * No special tcSimplifySuperClasss
        * No "dependents" argument to EvDFunApp
      
      IMPORTANT
         It turns out that it's quite tricky to generate the right
         DFunUnfolding for a specialised dfun, when you use SPECIALISE
         INSTANCE.  For now I've just commented it out (in DsBinds) but
         that'll lose some optimisation, and I need to get back to
         this.
      a3bab050
  3. 12 Nov, 2010 1 commit
    • simonpj@microsoft.com's avatar
      A (final) re-engineering of the new typechecker · c80364f8
      simonpj@microsoft.com authored
      Regression testing and user feedback for GHC 7.0 taught
      us a lot.  This patch fixes numerous small bugs, and some
      major ones (eg Trac #4484, #4492), and improves type
      error messages.
      
      The main changes are:
      
      * Entirely remove the "skolem equivalance class" stuff;
        a very useful simplification
      
      * Instead, when flattening "wanted" constraints we generate
        unification variables (not flatten-skolems) for the
        flattened type function application
      
      * We then need a fixup pass at the end, TcSimplify.solveCTyFunEqs,
        which resolves any residual equalities of form
            F xi ~ alpha
      
      * When we come across a definite failure (e.g. Int ~ [a]),
        we now defer reporting the error until the end, in case we
        learn more about 'a'.  That is particularly important for
        occurs-check errors.  These are called "frozen" type errors.
      
      * Other improvements in error message generation.
      
      * Better tracing messages
      c80364f8
  4. 22 Oct, 2010 1 commit
    • simonpj@microsoft.com's avatar
      Add rebindable syntax for if-then-else · 4e0c994e
      simonpj@microsoft.com authored
      There are two main changes
      
       * New LANGUAGE option RebindableSyntax, which implies NoImplicitPrelude
      
       * if-the-else becomes rebindable, with function name "ifThenElse"
         (but case expressions are unaffected)
      
      Thanks to Sam Anklesaria for doing most of the work here
      4e0c994e
  5. 13 Oct, 2010 1 commit
  6. 18 Sep, 2010 1 commit
  7. 15 Sep, 2010 1 commit
  8. 13 Sep, 2010 1 commit
  9. 29 Oct, 2009 1 commit
    • simonpj@microsoft.com's avatar
      The Big INLINE Patch: totally reorganise way that INLINE pragmas work · 72462499
      simonpj@microsoft.com authored
      This patch has been a long time in gestation and has, as a
      result, accumulated some extra bits and bobs that are only
      loosely related.  I separated the bits that are easy to split
      off, but the rest comes as one big patch, I'm afraid.
      
      Note that:
       * It comes together with a patch to the 'base' library
       * Interface file formats change slightly, so you need to
         recompile all libraries
      
      The patch is mainly giant tidy-up, driven in part by the
      particular stresses of the Data Parallel Haskell project. I don't
      expect a big performance win for random programs.  Still, here are the
      nofib results, relative to the state of affairs without the patch
      
              Program           Size    Allocs   Runtime   Elapsed
      --------------------------------------------------------------------------------
                  Min         -12.7%    -14.5%    -17.5%    -17.8%
                  Max          +4.7%    +10.9%     +9.1%     +8.4%
       Geometric Mean          +0.9%     -0.1%     -5.6%     -7.3%
      
      The +10.9% allocation outlier is rewrite, which happens to have a
      very delicate optimisation opportunity involving an interaction
      of CSE and inlining (see nofib/Simon-nofib-notes). The fact that
      the 'before' case found the optimisation is somewhat accidental.
      Runtimes seem to go down, but I never kno wwhether to really trust
      this number.  Binary sizes wobble a bit, but nothing drastic.
      
      
      The Main Ideas are as follows.
      
      InlineRules
      ~~~~~~~~~~~
      When you say 
            {-# INLINE f #-}
            f x = <rhs>
      you intend that calls (f e) are replaced by <rhs>[e/x] So we
      should capture (\x.<rhs>) in the Unfolding of 'f', and never meddle
      with it.  Meanwhile, we can optimise <rhs> to our heart's content,
      leaving the original unfolding intact in Unfolding of 'f'.
      
      So the representation of an Unfolding has changed quite a bit
      (see CoreSyn).  An INLINE pragma gives rise to an InlineRule 
      unfolding.  
      
      Moreover, it's only used when 'f' is applied to the
      specified number of arguments; that is, the number of argument on 
      the LHS of the '=' sign in the original source definition. 
      For example, (.) is now defined in the libraries like this
         {-# INLINE (.) #-}
         (.) f g = \x -> f (g x)
      so that it'll inline when applied to two arguments. If 'x' appeared
      on the left, thus
         (.) f g x = f (g x)
      it'd only inline when applied to three arguments.  This slightly-experimental
      change was requested by Roman, but it seems to make sense.
      
      Other associated changes
      
      * Moving the deck chairs in DsBinds, which processes the INLINE pragmas
      
      * In the old system an INLINE pragma made the RHS look like
         (Note InlineMe <rhs>)
        The Note switched off optimisation in <rhs>.  But it was quite
        fragile in corner cases. The new system is more robust, I believe.
        In any case, the InlineMe note has disappeared 
      
      * The workerInfo of an Id has also been combined into its Unfolding,
        so it's no longer a separate field of the IdInfo.
      
      * Many changes in CoreUnfold, esp in callSiteInline, which is the critical
        function that decides which function to inline.  Lots of comments added!
      
      * exprIsConApp_maybe has moved to CoreUnfold, since it's so strongly
        associated with "does this expression unfold to a constructor application".
        It can now do some limited beta reduction too, which Roman found 
        was an important.
      
      Instance declarations
      ~~~~~~~~~~~~~~~~~~~~~
      It's always been tricky to get the dfuns generated from instance
      declarations to work out well.  This is particularly important in 
      the Data Parallel Haskell project, and I'm now on my fourth attempt,
      more or less.
      
      There is a detailed description in TcInstDcls, particularly in
      Note [How instance declarations are translated].   Roughly speaking
      we now generate a top-level helper function for every method definition
      in an instance declaration, so that the dfun takes a particularly
      stylised form:
        dfun a d1 d2 = MkD (op1 a d1 d2) (op2 a d1 d2) ...etc...
      
      In fact, it's *so* stylised that we never need to unfold a dfun.
      Instead ClassOps have a special rewrite rule that allows us to
      short-cut dictionary selection.  Suppose dfun :: Ord a -> Ord [a]
                                                  d :: Ord a
      Then   
          compare (dfun a d)  -->   compare_list a d 
      in one rewrite, without first inlining the 'compare' selector
      and the body of the dfun.
      
      To support this
      a) ClassOps have a BuiltInRule (see MkId.dictSelRule)
      b) DFuns have a special form of unfolding (CoreSyn.DFunUnfolding)
         which is exploited in CoreUnfold.exprIsConApp_maybe
      
      Implmenting all this required a root-and-branch rework of TcInstDcls
      and bits of TcClassDcl.
      
      
      Default methods
      ~~~~~~~~~~~~~~~
      If you give an INLINE pragma to a default method, it should be just
      as if you'd written out that code in each instance declaration, including
      the INLINE pragma.  I think that it now *is* so.  As a result, library
      code can be simpler; less duplication.
      
      
      The CONLIKE pragma
      ~~~~~~~~~~~~~~~~~~
      In the DPH project, Roman found cases where he had
      
         p n k = let x = replicate n k
                 in ...(f x)...(g x)....
      
         {-# RULE f (replicate x) = f_rep x #-}
      
      Normally the RULE would not fire, because doing so involves 
      (in effect) duplicating the redex (replicate n k).  A new
      experimental modifier to the INLINE pragma, {-# INLINE CONLIKE
      replicate #-}, allows you to tell GHC to be prepared to duplicate
      a call of this function if it allows a RULE to fire.
      
      See Note [CONLIKE pragma] in BasicTypes
      
      
      Join points
      ~~~~~~~~~~~
      See Note [Case binders and join points] in Simplify
      
      
      Other refactoring
      ~~~~~~~~~~~~~~~~~
      * I moved endPass from CoreLint to CoreMonad, with associated jigglings
      
      * Better pretty-printing of Core
      
      * The top-level RULES (ones that are not rules for locally-defined things)
        are now substituted on every simplifier iteration.  I'm not sure how
        we got away without doing this before.  This entails a bit more plumbing
        in SimplCore.
      
      * The necessary stuff to serialise and deserialise the new
        info across interface files.
      
      * Something about bottoming floats in SetLevels
            Note [Bottoming floats]
      
      * substUnfolding has moved from SimplEnv to CoreSubs, where it belongs
      
      
      --------------------------------------------------------------------------------
              Program           Size    Allocs   Runtime   Elapsed
      --------------------------------------------------------------------------------
                 anna          +2.4%     -0.5%      0.16      0.17
                 ansi          +2.6%     -0.1%      0.00      0.00
                 atom          -3.8%     -0.0%     -1.0%     -2.5%
               awards          +3.0%     +0.7%      0.00      0.00
               banner          +3.3%     -0.0%      0.00      0.00
           bernouilli          +2.7%     +0.0%     -4.6%     -6.9%
                boyer          +2.6%     +0.0%      0.06      0.07
               boyer2          +4.4%     +0.2%      0.01      0.01
                 bspt          +3.2%     +9.6%      0.02      0.02
            cacheprof          +1.4%     -1.0%    -12.2%    -13.6%
             calendar          +2.7%     -1.7%      0.00      0.00
             cichelli          +3.7%     -0.0%      0.13      0.14
              circsim          +3.3%     +0.0%     -2.3%     -9.9%
             clausify          +2.7%     +0.0%      0.05      0.06
        comp_lab_zift          +2.6%     -0.3%     -7.2%     -7.9%
             compress          +3.3%     +0.0%     -8.5%     -9.6%
            compress2          +3.6%     +0.0%    -15.1%    -17.8%
          constraints          +2.7%     -0.6%    -10.0%    -10.7%
         cryptarithm1          +4.5%     +0.0%     -4.7%     -5.7%
         cryptarithm2          +4.3%    -14.5%      0.02      0.02
                  cse          +4.4%     -0.0%      0.00      0.00
                eliza          +2.8%     -0.1%      0.00      0.00
                event          +2.6%     -0.0%     -4.9%     -4.4%
               exp3_8          +2.8%     +0.0%     -4.5%     -9.5%
               expert          +2.7%     +0.3%      0.00      0.00
                  fem          -2.0%     +0.6%      0.04      0.04
                  fft          -6.0%     +1.8%      0.05      0.06
                 fft2          -4.8%     +2.7%      0.13      0.14
             fibheaps          +2.6%     -0.6%      0.05      0.05
                 fish          +4.1%     +0.0%      0.03      0.04
                fluid          -2.1%     -0.2%      0.01      0.01
               fulsom          -4.8%     +9.2%     +9.1%     +8.4%
               gamteb          -7.1%     -1.3%      0.10      0.11
                  gcd          +2.7%     +0.0%      0.05      0.05
          gen_regexps          +3.9%     -0.0%      0.00      0.00
               genfft          +2.7%     -0.1%      0.05      0.06
                   gg          -2.7%     -0.1%      0.02      0.02
                 grep          +3.2%     -0.0%      0.00      0.00
               hidden          -0.5%     +0.0%    -11.9%    -13.3%
                  hpg          -3.0%     -1.8%     +0.0%     -2.4%
                  ida          +2.6%     -1.2%      0.17     -9.0%
                infer          +1.7%     -0.8%      0.08      0.09
              integer          +2.5%     -0.0%     -2.6%     -2.2%
            integrate          -5.0%     +0.0%     -1.3%     -2.9%
              knights          +4.3%     -1.5%      0.01      0.01
                 lcss          +2.5%     -0.1%     -7.5%     -9.4%
                 life          +4.2%     +0.0%     -3.1%     -3.3%
                 lift          +2.4%     -3.2%      0.00      0.00
            listcompr          +4.0%     -1.6%      0.16      0.17
             listcopy          +4.0%     -1.4%      0.17      0.18
             maillist          +4.1%     +0.1%      0.09      0.14
               mandel          +2.9%     +0.0%      0.11      0.12
              mandel2          +4.7%     +0.0%      0.01      0.01
              minimax          +3.8%     -0.0%      0.00      0.00
              mkhprog          +3.2%     -4.2%      0.00      0.00
           multiplier          +2.5%     -0.4%     +0.7%     -1.3%
             nucleic2          -9.3%     +0.0%      0.10      0.10
                 para          +2.9%     +0.1%     -0.7%     -1.2%
            paraffins         -10.4%     +0.0%      0.20     -1.9%
               parser          +3.1%     -0.0%      0.05      0.05
              parstof          +1.9%     -0.0%      0.00      0.01
                  pic          -2.8%     -0.8%      0.01      0.02
                power          +2.1%     +0.1%     -8.5%     -9.0%
               pretty         -12.7%     +0.1%      0.00      0.00
               primes          +2.8%     +0.0%      0.11      0.11
            primetest          +2.5%     -0.0%     -2.1%     -3.1%
               prolog          +3.2%     -7.2%      0.00      0.00
               puzzle          +4.1%     +0.0%     -3.5%     -8.0%
               queens          +2.8%     +0.0%      0.03      0.03
              reptile          +2.2%     -2.2%      0.02      0.02
              rewrite          +3.1%    +10.9%      0.03      0.03
                 rfib          -5.2%     +0.2%      0.03      0.03
                  rsa          +2.6%     +0.0%      0.05      0.06
                  scc          +4.6%     +0.4%      0.00      0.00
                sched          +2.7%     +0.1%      0.03      0.03
                  scs          -2.6%     -0.9%     -9.6%    -11.6%
               simple          -4.0%     +0.4%    -14.6%    -14.9%
                solid          -5.6%     -0.6%     -9.3%    -14.3%
              sorting          +3.8%     +0.0%      0.00      0.00
               sphere          -3.6%     +8.5%      0.15      0.16
               symalg          -1.3%     +0.2%      0.03      0.03
                  tak          +2.7%     +0.0%      0.02      0.02
            transform          +2.0%     -2.9%     -8.0%     -8.8%
             treejoin          +3.1%     +0.0%    -17.5%    -17.8%
            typecheck          +2.9%     -0.3%     -4.6%     -6.6%
              veritas          +3.9%     -0.3%      0.00      0.00
                 wang          -6.2%     +0.0%      0.18     -9.8%
            wave4main         -10.3%     +2.6%     -2.1%     -2.3%
         wheel-sieve1          +2.7%     -0.0%     +0.3%     -0.6%
         wheel-sieve2          +2.7%     +0.0%     -3.7%     -7.5%
                 x2n1          -4.1%     +0.1%      0.03      0.04
      --------------------------------------------------------------------------------
                  Min         -12.7%    -14.5%    -17.5%    -17.8%
                  Max          +4.7%    +10.9%     +9.1%     +8.4%
       Geometric Mean          +0.9%     -0.1%     -5.6%     -7.3%
      72462499
  10. 10 Sep, 2009 1 commit
    • simonpj@microsoft.com's avatar
      Three improvements to Template Haskell (fixes #3467) · 1e436f2b
      simonpj@microsoft.com authored
      This patch implements three significant improvements to Template Haskell.
        
      Declaration-level splices with no "$" 
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      This change simply allows you to omit the "$(...)" wrapper for 
      declaration-level TH splices.  An expression all by itself is
      not legal, so we now treat it as a TH splice.  Thus you can now
      say
      	data T = T1 | T2
       	deriveMyStuff ''T
      
      where deriveMyStuff :: Name -> Q [Dec]
      This makes a much nicer interface for clients of libraries that use
      TH: no scary $(deriveMyStuff ''T).
      
      Nested top-level splices
      ~~~~~~~~~~~~~~~~~~~~~~~~
      Previously TH would reject this, saying that splices cannot be nested:
      	f x = $(g $(h 'x))
      But there is no reason for this not to work.  First $(h 'x) is run,
      yielding code <blah> that is spliced instead of the $(h 'x). Then (g
      <blah>) is typechecked and run, yielding code that replaces the
      $(g ...) splice.  
      
      So this simply lifts the restriction.
      
      Fix Trac #3467: non-top-level type splices
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      It appears that when I added the ability to splice types in TH
      programs, I failed to pay attention to non-top-level splices -- that
      is, splices inside quotatation brackets.  
      
      This patch fixes the problem.  I had to modify HsType, so there's a
      knock-on change to Haddock.
      
      Its seems that a lot of lines of code has changed, but almost all the
      new lines are comments!
      
      General tidying up
      ~~~~~~~~~~~~~~~~~~
      As a result of thinking all this out I re-jigged the data type ThStage,
      which had far too many values before.  And I wrote a nice state transition
      diagram to make it all precise; 
         see Note [Template Haskell state diagram] in TcSplice
      
      Lots more refactoring in TcSplice, resulting in significantly less code.
      (A few more lines, but actually less code -- the rest is comments.)
      
      I think the result is significantly cleaner.
      1e436f2b
  11. 20 Aug, 2009 1 commit
  12. 03 Jun, 2009 1 commit
    • simonpj@microsoft.com's avatar
      Allow RULES for seq, and exploit them · 90ce88a0
      simonpj@microsoft.com authored
      Roman found situations where he had
            case (f n) of _ -> e
      where he knew that f (which was strict in n) would terminate if n did.
      Notice that the result of (f n) is discarded. So it makes sense to
      transform to
            case n of _ -> e
      
      Rather than attempt some general analysis to support this, I've added
      enough support that you can do this using a rewrite rule:
      
        RULE "f/seq" forall n.  seq (f n) e = seq n e
      
      You write that rule.  When GHC sees a case expression that discards
      its result, it mentally transforms it to a call to 'seq' and looks for
      a RULE.  (This is done in Simplify.rebuildCase.)  As usual, the
      correctness of the rule is up to you.
      
      This patch implements the extra stuff.  I have not documented it explicitly
      in the user manual yet... let's see how useful it is first.
      
      The patch looks bigger than it is, because
        a) Comments; see esp MkId Note [seqId magic]
      
        b) Some refactoring.  Notably, I moved the special desugaring for
           seq from MkCore back into DsUtils where it properly belongs.
           (It's really a desugaring thing, not a CoreSyn invariant.)
      
        c) Annoyingly, in a RULE left-hand side we need to be careful that
           the magical desugaring done in MkId Note [seqId magic] item (c) 
           is *not* done on the LHS of a rule. Or rather, we arrange to 
           un-do it, in DsBinds.decomposeRuleLhs.
      
      90ce88a0
  13. 28 May, 2009 1 commit
  14. 27 Apr, 2009 1 commit
    • chak@cse.unsw.edu.au.'s avatar
      Equality constraint solver is now externally pure · 296058a1
      chak@cse.unsw.edu.au. authored
      - This patch changes the equality constraint solver such that it does not
        instantiate any type variables that occur in the constraints that are to be
        solved (or in the environment).  Instead, it returns a bag of type bindings.
      - If these type bindings (together with the other results of the solver) are
        discarded, solver invocation has no effect (outside the solver) and can be
        repeated (that's imported for TcSimplifyRestricted).
      - For the type bindings to take effect, the caller of the solver needs to 
        execute them. 
      - The solver will still instantiate type variables thet were created during 
        solving (e.g., skolem flexibles used during type flattening).
      
        See also http://hackage.haskell.org/trac/ghc/wiki/TypeFunctionsSolving
      296058a1
  15. 15 Mar, 2009 1 commit
  16. 11 Feb, 2009 1 commit
    • simonpj@microsoft.com's avatar
      Fix Trac #3017: ensure that we quantify over enough type variables when equalities are involved · e5a8d57c
      simonpj@microsoft.com authored
      The function FunDeps.grow was not doing the right thing when type equality
      constraints were involved.  That wasn't really its fault: its input was
      being filtered by fdPredsOfInsts.
      
      To fix this I did a bit of refactoring, so that the (revolting) fdPredsOfInsts
      is now less important (maybe we can get rid of it in due course).  The 'grow'
      function moves from FunDeps to
      	 Inst.growInstsTyVars
      	 TcMTType.growThetaTyVars
      	 TcMType.growTyVars
      
      The main comments are with the first of these, in
      Note [Growing the tau-tvs using constraints] in Inst.
      
      Push to the branch if conflict free.
      
      e5a8d57c
  17. 16 Dec, 2008 1 commit
    • 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
  18. 05 Dec, 2008 1 commit
    • simonpj@microsoft.com's avatar
      Completely new treatment of INLINE pragmas (big patch) · d95ce839
      simonpj@microsoft.com authored
      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.
      d95ce839
  19. 03 Oct, 2008 1 commit
  20. 01 Oct, 2008 2 commits
  21. 16 Sep, 2008 1 commit
  22. 15 Sep, 2008 1 commit
  23. 14 Sep, 2008 1 commit
  24. 13 Sep, 2008 1 commit
    • chak@cse.unsw.edu.au.'s avatar
      Type families: completed the new equality solver · e8917205
      chak@cse.unsw.edu.au. authored
      - Implements normalisation of class constraints containing synonym family
        applications or skolems refined by local equalities.
      - Clean up of TcSimplify.reduceContext by using the new equality solver.
      - Removed all the now unused code of the old algorithm.
      - This completes the implementation of the new algorithm, but it is largely
        untested => many regressions.
      e8917205
  25. 10 Sep, 2008 1 commit
  26. 07 Sep, 2008 1 commit
  27. 31 Jul, 2008 1 commit
  28. 16 Jun, 2008 1 commit
    • Ian Lynagh's avatar
      More commandline flag improvements · 0f5e104c
      Ian Lynagh authored
      * Allow -ffoo flags to be deprecated
      * Mark some -ffoo flags as deprecated
      * Avoid using deprecated flags in error messages, in the build system, etc
      * Add a flag to en/disable the deprecated flag warning
      0f5e104c
  29. 05 Jun, 2008 1 commit
  30. 10 May, 2008 2 commits
  31. 06 May, 2008 3 commits
    • Ian Lynagh's avatar
      Make Inst warning-free · dbe50b77
      Ian Lynagh authored
      dbe50b77
    • Ian Lynagh's avatar
      Add a panic for lookupPred EqPred · 869feb6a
      Ian Lynagh authored
      It's possible that returning Nothing was the right thing to do here,
      but the comment and variable name indicated that it was written for
      implicit parameters, so make it a panic for now just in case.
      869feb6a
    • simonpj@microsoft.com's avatar
      Fix Trac #2246; overhaul handling of overloaded literals · ecdaf6bc
      simonpj@microsoft.com authored
      The real work of fixing Trac #2246 is to use shortCutLit in
      MatchLit.dsOverLit, so that type information discovered late in the
      day by the type checker can still be exploited during desugaring.
      
      However, as usual I found myself doing some refactoring along the
      way, to tidy up the handling of overloaded literals.   The main
      change is to split HsOverLit into a record, which in turn uses
      a sum type for the three variants.  This makes the code significantly
      more modular.
      
      data HsOverLit id
        = OverLit {
      	ol_val :: OverLitVal, 
      	ol_rebindable :: Bool,		-- True <=> rebindable syntax
      					-- False <=> standard syntax
      	ol_witness :: SyntaxExpr id,	-- Note [Overloaded literal witnesses]
      	ol_type :: PostTcType }
      
      data OverLitVal
        = HsIntegral   !Integer   	-- Integer-looking literals;
        | HsFractional !Rational   	-- Frac-looking literals
        | HsIsString   !FastString 	-- String-looking literals
      ecdaf6bc
  32. 23 Apr, 2008 1 commit
  33. 12 Apr, 2008 1 commit
  34. 29 Mar, 2008 1 commit
  35. 06 Mar, 2008 1 commit
    • simonpj@microsoft.com's avatar
      Fix Trac #783: improve short-cutting literals in the type checker · 0a8ad35f
      simonpj@microsoft.com authored
      The Inst.shortCutIntLit mechanism in the type checker was missing cases
      where a floating-point literal was given without an explicit decimal point.
      
      As a result, programs with lots of floating-point literals (without decimals)
      ended up with massive Static Reference Tables.  This is not cool.  See
      comments with Trac #783 for details.
      
      0a8ad35f
  36. 29 Feb, 2008 1 commit