1. 02 Oct, 2008 1 commit
    • rl@cse.unsw.edu.au's avatar
      Prevent excessive inlining with DPH · 444c6250
      rl@cse.unsw.edu.au authored
      This adds a new flag -finline-if-enough-args which disables inlining for
      partially applied functions. It is automatically set by -Odph. This is a
      temporary hack and should remain undocumented.
      
      MERGE TO 6.10
      444c6250
  2. 14 Sep, 2008 1 commit
  3. 10 Sep, 2008 1 commit
    • simonpj@microsoft.com's avatar
      Fix Trac #2581: inlining of record selectors · 112ad197
      simonpj@microsoft.com authored
      Bryan discovered that a non-trivial record selector (non-trivial in 
      the sense that it has to reconstruct the result value because of
      UNPACK directives) weren't being inlined.  The reason was that the
      unfolding generated by MkId.mRecordSelId was never being optimised
      *at all*, and hence looked big, and hence wasn't inlined.
      
      (The out-of-line version *is* put into the code of the module
      and *is* optimised, which made this bug pretty puzzling.  But the
      unfolding inside the record-selector-Id itself, which is a GlobalId
      and hence does not get its inlining updated like LocalIds, was
      big and fat.)
      
      Solution: I wrote a very simple optimiser, CoreUnfold.simplOptExpr,
      which does enough optimisation to solve this particular problem.
      It's short, simple, and will be useful in other contexts.
      112ad197
  4. 09 Sep, 2008 1 commit
    • simonpj@microsoft.com's avatar
      Important performance wibble to callSiteInline (the n_vals_wanted > 0 thing) · e71d6d1f
      simonpj@microsoft.com authored
      See Note [Inlining in ArgCtxt].  This very small change gives quite a
      big performance win. Just showing the bigger ones:
      
              Program           Size    Allocs   Runtime
      --------------------------------------------------------------------------------
                 anna          -0.7%     -4.3%      0.15
             cichelli          -0.6%     -6.4%      0.15
               fulsom          -0.4%    -18.5%     -8.1%
                  gcd          -0.6%    -12.0%      0.06
              integer          -0.6%    -16.2%     -8.4%
                power          -0.7%    -19.3%     -4.8%
      --------------------------------------------------------------------------------
                  Min          -0.7%    -19.3%    -15.7%
                  Max          -0.1%     +0.1%     +5.7%
       Geometric Mean          -0.6%     -1.9%     -4.3%
      
      The original change was to improve a case that Roman found (see test
      eyeball/inline1) but that seems to work ok now anyway.
      
      e71d6d1f
  5. 12 Apr, 2008 1 commit
  6. 29 Mar, 2008 1 commit
  7. 07 Feb, 2008 1 commit
    • simonpj@microsoft.com's avatar
      Redo inlining patch, plus some tidying up · fa1c8a7e
      simonpj@microsoft.com authored
      This adds back in the patch 
        * UNDO: Be a little keener to inline
      
      It originally broke the compiler because it tickled a Cmm optimisation bug,
      now fixed.  
      
      In revisiting this I have also make inlining a bit cleverer, in response to
      more examples from Roman. In particular
      
        * CoreUnfold.CallCtxt is a data type that tells something about
          the context of a call.  The new feature is that if the context is
          the argument position of a function call, we record both 
      	- whether the function (or some higher up function) has rules
      	- what the argument discount in that position is
          Either of these make functions keener to inline, even if it's
          in a lazy position
      
        * There was conseqential tidying up on the data type of CallCont.
          In particular I got rid of the now-unused LetRhsFlag
      
      
      fa1c8a7e
  8. 01 Feb, 2008 1 commit
    • Simon Marlow's avatar
      UNDO: Be a little keener to inline · 2859b531
      Simon Marlow authored
      This patch caused at least the following test failures:
         1744(normal)
         ghci028(ghci)
         unicode001(normal)
      and additionally made the stage3 build fail.  
      
      A little more validation please!
      
      I didn't find the exact cause of the failure yet, but it appears that
      the Lexer is miscompiled in some strange way.  If any of {Encoding,
      StringBuffer, or Lexer} are compiled without -O, the problem goes
      away.
      2859b531
  9. 25 Jan, 2008 2 commits
  10. 17 Jan, 2008 1 commit
    • Isaac Dupree's avatar
      lots of portability changes (#1405) · 206b4dec
      Isaac Dupree authored
      re-recording to avoid new conflicts was too hard, so I just put it
      all in one big patch :-(  (besides, some of the changes depended on
      each other.)  Here are what the component patches were:
      
      Fri Dec 28 11:02:55 EST 2007  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * document BreakArray better
      
      Fri Dec 28 11:39:22 EST 2007  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * properly ifdef BreakArray for GHCI
      
      Fri Jan  4 13:50:41 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * change ifs on __GLASGOW_HASKELL__ to account for... (#1405)
        for it not being defined. I assume it being undefined implies
        a compiler with relatively modern libraries but without most
        unportable glasgow extensions.
      
      Fri Jan  4 14:21:21 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * MyEither-->EitherString to allow Haskell98 instance
      
      Fri Jan  4 16:13:29 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * re-portabilize Pretty, and corresponding changes
      
      Fri Jan  4 17:19:55 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * Augment FastTypes to be much more complete
      
      Fri Jan  4 20:14:19 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * use FastFunctions, cleanup FastString slightly
      
      Fri Jan  4 21:00:22 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * Massive de-"#", mostly Int# --> FastInt (#1405)
      
      Fri Jan  4 21:02:49 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * miscellaneous unnecessary-extension-removal
      
      Sat Jan  5 19:30:13 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
        * add FastFunctions
      206b4dec
  11. 04 Dec, 2007 1 commit
    • simonpj@microsoft.com's avatar
      Improve inlining for INLINE non-functions · 30c39066
      simonpj@microsoft.com authored
      	
      (No need to merge to 6.8, but no harm if a subsequent patch needs it.)
      
      The proximate cause for this patch is to improve the inlining for INLINE
      things that are not functions; this came up in the NDP project.  See
      Note [Lone variables] in CoreUnfold.
      
      This caused some refactoring that actually made things simpler.  In 
      particular, more of the inlining logic has moved from SimplUtils to 
      CoreUnfold, where it belongs.
      
      30c39066
  12. 04 Sep, 2007 1 commit
  13. 03 Sep, 2007 1 commit
  14. 01 Sep, 2007 1 commit
  15. 09 Feb, 2007 1 commit
    • simonpj@microsoft.com's avatar
      Major improvement to SpecConstr · cac2aca1
      simonpj@microsoft.com authored
      This patch improves the SpecConstr pass, by 
        a) making it work with join points
        b) making it generate specialisations transitively
      
      As part of it, SpecConstr now carries a substitution with it, which
      runs over the whole program as it goes.  This turned out to be 
      a big win; simplified the implementation quite a bit.
      
      I have *disabled* the specialisation on lambdas; it's pretty fragile,
      and sometimes generates more and more specialisations. Something to
      come back to, perhaps.
      
      I rejigged the flag-handling a bit.  Now the specification of passes
      in DynFlags is a bit nicer; see
      	- optLevelFlags top-level data structure
      	- runWhen function
      	- CoreDoPasses constructor
      
      There are now command-line flags
      	-fspec-constr
      	-fliberate-case
      	-fspec-threshold=N
      which do the obvious thing.  -O2 switches on both spec-constr and liberate-case.
      You can use -fno-liberate-case, -fno-spec-constr after -O2 to switch them off again.
      
      The spec-threshold applies to both these transformations; default value 200 for now.
      
      
      
      
      cac2aca1
  16. 11 Oct, 2006 1 commit
    • Simon Marlow's avatar
      Module header tidyup, phase 1 · 49c98d14
      Simon Marlow authored
      This patch is a start on removing import lists and generally tidying
      up the top of each module.  In addition to removing import lists:
      
         - Change DATA.IOREF -> Data.IORef etc.
         - Change List -> Data.List etc.
         - Remove $Id$
         - Update copyrights
         - Re-order imports to put non-GHC imports last
         - Remove some unused and duplicate imports
      49c98d14
  17. 05 Oct, 2006 2 commits
    • simonpj@microsoft.com's avatar
      Remove unused OccInfo (simplification) · b6cc5851
      simonpj@microsoft.com authored
      The substitution used to carry "fragile" OccInfo to call sites via the
      DoneId constructor of SimplEnv.SimplSR.  This was always a tricky thing 
      to do, and for some time I've been removing the need for it.
      
      Now at last I think we can nuke it altogether.  Hooray.
      
      I did a full nonfib run, and got zero perf changes.
      b6cc5851
    • simonpj@microsoft.com's avatar
      Take 2 on the recursive-rule fix · 805edf6e
      simonpj@microsoft.com authored
      This is another attempt to fix the interaction between recursion and
      RULES.  I just had it wrong before!  Now the significance of the
      flag on IAmALoopBreaker is given in BasicTypes
      
        | IAmALoopBreaker	-- Used by the occurrence analyser to mark loop-breakers
      			-- in a group of recursive definitions
      	!RulesOnly	-- True <=> This loop breaker mentions the other binders
      			--	    in its recursive group only in its RULES, not
      			--	    in its rhs
      			--  See OccurAnal Note [RulesOnly]
      805edf6e
  18. 04 Oct, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Second bite at the rules-only idea · a35f75aa
      simonpj@microsoft.com authored
      This is part 2 of the patch that improved the interaction of RULES and
      recursion.  It's vital that all Ids that may be referred to from later in
      the module are marked 'IAmALoopBreaker' because otherwise we may do
      postInlineUnconditionally, and lose the binding altogether. 
      
      So I've added a boolean rules-only flag to IAmALoopBreaker.  Now we can
      do inlining for rules-only loop-breakers. 
      a35f75aa
  19. 04 Aug, 2006 1 commit
  20. 05 Jun, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Remove InlinePlease and add inline function and RULE · f2dcf256
      simonpj@microsoft.com authored
      For a long time GHC has had some internal mechanism designed to support
      a call-site inline directive, thus
      	inline f xs
      makes f be inlined at the call site even if f is big.
      
      However, the surface syntax seems to have gone, and in any case it
      can be done more neatly using a RULE.
      
      This commit:
        * Removes the InlineCall constructor for Note
          and InlinePlease for SimplCont
      
        * Adds a new known-key Id called 'inline', whose definition in
          GHC.Base is just the identity function
      
        * Adds a built-in RULE in PrelRules that rewrites (inline f) to
          the body of f, if possible
      
        * Adds documentation
      
      NOTE: I have not tested this (aeroplane work).  Give it a try!
      f2dcf256
  21. 04 May, 2006 1 commit
  22. 07 Apr, 2006 1 commit
    • Simon Marlow's avatar
      Reorganisation of the source tree · 0065d5ab
      Simon Marlow authored
      Most of the other users of the fptools build system have migrated to
      Cabal, and with the move to darcs we can now flatten the source tree
      without losing history, so here goes.
      
      The main change is that the ghc/ subdir is gone, and most of what it
      contained is now at the top level.  The build system now makes no
      pretense at being multi-project, it is just the GHC build system.
      
      No doubt this will break many things, and there will be a period of
      instability while we fix the dependencies.  A straightforward build
      should work, but I haven't yet fixed binary/source distributions.
      Changes to the Building Guide will follow, too.
      0065d5ab
  23. 14 Oct, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-10-14 11:22:41 by simonpj] · 36436bc6
      simonpj authored
      Add record syntax for GADTs
      	~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      Atrijus Tang wanted to add record syntax for GADTs and existential
      types, so he and I worked on it a bit at ICFP.  This commit is the
      result.  Now you can say
      
       data T a where
        T1 { x :: a }           	 :: T [a]
        T2 { x :: a, y :: Int } 	 :: T [a]
        forall b. Show b =>
       	T3 { naughty :: b, ok :: Int } :: T Int
        T4 :: Eq a => a -> b -> T (a,b)
      
      Here the constructors are declared using record syntax.
      
      Still to come after this commit:
        - User manual documentation
        - More regression tests
        - Some missing cases in the parser (e.g. T3 won't parse)
      Autrijus is going to do these.
      
      
      Here's a quick summary of the rules.  (Atrijus is going to write
      proper documentation shortly.)
      
      Defnition: a 'vanilla' constructor has a type of the form
      	forall a1..an. t1 -> ... -> tm -> T a1 ... an
      No existentials, no context, nothing.  A constructor declared with
      Haskell-98 syntax is vanilla by construction.  A constructor declared
      with GADT-style syntax is vanilla iff its type looks like the above.
      (In the latter case, the order of the type variables does not matter.)
      
      * You can mix record syntax and non-record syntax in a single decl
      
      * All constructors that share a common field 'x' must have the
        same result type (T [a] in the example).
      
      * You can use field names without restriction in record construction
        and record pattern matching.
      
      * Record *update* only works for data types that only have 'vanilla'
        constructors.
      
      * Consider the field 'naughty', which uses a type variable that does
        not appear in the result type ('b' in the example).  You can use the
        field 'naughty' in pattern matching and construction, but NO
        SELECTOR function is generated for 'naughty'.  [An attempt to use
        'naughty' as a selector function will elicit a helpful error
        message.]
      
      * Data types declared in GADT syntax cannot have a context. So this
      is illegal:
      	data (Monad m) => T a where
      		  ....
      
      * Constructors in GADT syntax can have a context (t.g. T3, T4 above)
        and that context is stored in the constructor and made available
        when the constructor is pattern-matched on.  WARNING: not competely
        implemented yet, but that's the plan.
      
      
      
      Implementation notes
      ~~~~~~~~~~~~~~~~~~~~
      - Data constructors (even vanilla ones) no longer share the type
        variables of their parent type constructor.
      
      - HsDecls.ConDecl has changed quite a bit
      
      - TyCons don't record the field labels and type any more (doesn't
        make sense for existential fields)
      
      - GlobalIdDetails records which selectors are 'naughty', and hence
        don't have real code.
      36436bc6
  24. 12 Aug, 2005 1 commit
    • simonmar's avatar
      [project @ 2005-08-12 10:45:36 by simonmar] · 196ccd21
      simonmar authored
      More inlining changes from SimonPJ & me: The Plan is to avoid relying
      on knowledge of OneOcc occurrences after postInlineUnconditionally, so
      we now attempt to make use of OneOcc as far as possible in in
      pre/postInlineUnconditionally rather than the call site.  Plenty of
      comments in the code with more details.
      
      This change almost always improves performance on nofib; we have one
      program that goes slower, which we'll investigate in due course.
      196ccd21
  25. 10 Aug, 2005 1 commit
  26. 09 Aug, 2005 1 commit
  27. 04 Aug, 2005 1 commit
  28. 03 Aug, 2005 1 commit
    • simonmar's avatar
      [project @ 2005-08-03 13:53:35 by simonmar] · cfd9e9b3
      simonmar authored
      Patch from SimonPJ (slightly tweaked by me after checking performance
      results):
      
      Fix occasional O(n^2) behaviour in the simplifier.  There was a
      possibility that by inlining a binding, we could re-simplify an
      arbitrary sized expression.  This patch fixes it by moving the
      inlining of arbitrary-sized expressiong to the binding site
      (preInlineUnconditionally), so the decision to inline happens before
      simplifying the RHS.  To do this, we have to collect more information
      during the occurrence analysis phase.
      
      We still make inlining decisions at the call site, but they are always
      size-limited, so we can't get quadratic blowup.
      cfd9e9b3
  29. 19 Jul, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-07-19 16:44:50 by simonpj] · a7ecdf96
      simonpj authored
      WARNING: this is a big commit.  You might want 
      	to wait a few days before updating, in case I've 
      	broken something.
      
      	However, if any of the changes are what you wanted,
      	please check it out and test!
      
      This commit does three main things:
      
      1. A re-organisation of the way that GHC handles bindings in HsSyn.
         This has been a bit of a mess for quite a while.  The key new
         types are
      
      	-- Bindings for a let or where clause
      	data HsLocalBinds id
      	  = HsValBinds (HsValBinds id)
      	  | HsIPBinds  (HsIPBinds id)
      	  | EmptyLocalBinds
      
      	-- Value bindings (not implicit parameters)
      	data HsValBinds id
      	  = ValBindsIn  -- Before typechecking
      		(LHsBinds id) [LSig id]	-- Not dependency analysed
      					-- Recursive by default
      
      	  | ValBindsOut	-- After typechecking
      		[(RecFlag, LHsBinds id)]-- Dependency analysed
      
      2. Implement Mark Jones's idea of increasing polymoprhism
         by using type signatures to cut the strongly-connected components
         of a recursive group.  As a consequence, GHC no longer insists
         on the contexts of the type signatures of a recursive group
         being identical.
      
         This drove a significant change: the renamer no longer does dependency
         analysis.  Instead, it attaches a free-variable set to each binding,
         so that the type checker can do the dep anal.  Reason: the typechecker
         needs to do *two* analyses:
      	one to find the true mutually-recursive groups
      		(which we need so we can build the right CoreSyn)
      	one to find the groups in which to typecheck, taking
      		account of type signatures
      
      3. Implement non-ground SPECIALISE pragmas, as promised, and as
         requested by Remi and Ross.  Certainly, this should fix the 
         current problem with GHC, namely that if you have
      	g :: Eq a => a -> b -> b
         then you can now specialise thus
      	SPECIALISE g :: Int -> b -> b
          (This didn't use to work.)
      
         However, it goes further than that.  For example:
      	f :: (Eq a, Ix b) => a -> b -> b
         then you can make a partial specialisation
      	SPECIALISE f :: (Eq a) => a -> Int -> Int
      
          In principle, you can specialise f to *any* type that is
          "less polymorphic" (in the sense of subsumption) than f's 
          actual type.  Such as
      	SPECIALISE f :: Eq a => [a] -> Int -> Int
          But I haven't tested that.
      
          I implemented this by doing the specialisation in the typechecker
          and desugarer, rather than leaving around the strange SpecPragmaIds,
          for the specialiser to find.  Indeed, SpecPragmaIds have vanished 
          altogether (hooray).
      
          Pragmas in general are handled more tidily.  There's a new
          data type HsBinds.Prag, which lives in an AbsBinds, and carries
          pragma info from the typechecker to the desugarer.
      
      
      Smaller things
      
      - The loop in the renamer goes via RnExpr, instead of RnSource.
        (That makes it more like the type checker.)
      
      - I fixed the thing that was causing 'check_tc' warnings to be 
        emitted.
      a7ecdf96
  30. 16 May, 2005 1 commit
  31. 31 Mar, 2005 1 commit
    • simonmar's avatar
      [project @ 2005-03-31 10:16:33 by simonmar] · 853e20a3
      simonmar authored
      Tweaks to get the GHC sources through Haddock.  Doesn't quite work
      yet, because Haddock complains about the recursive modules.  Haddock
      needs to understand SOURCE imports (it can probably just ignore them
      as a first attempt).
      853e20a3
  32. 18 Mar, 2005 1 commit
    • simonmar's avatar
      [project @ 2005-03-18 13:37:27 by simonmar] · d1c1b7d0
      simonmar authored
      Flags cleanup.
      
      Basically the purpose of this commit is to move more of the compiler's
      global state into DynFlags, which is moving in the direction we need
      to go for the GHC API which can have multiple active sessions
      supported by a single GHC instance.
      
      Before:
      
      $ grep 'global_var' */*hs | wc -l
           78
      
      After:
      
      $ grep 'global_var' */*hs | wc -l
           27
      
      Well, it's an improvement.  Most of what's left won't really affect
      our ability to host multiple sessions.
      
      Lots of static flags have become dynamic flags (yay!).  Notably lots
      of flags that we used to think of as "driver" flags, like -I and -L,
      are now dynamic.  The most notable static flags left behind are the
      "way" flags, eg. -prof.  It would be nice to fix this, but it isn't
      urgent.
      
      On the way, lots of cleanup has happened.  Everything related to
      static and dynamic flags lives in StaticFlags and DynFlags
      respectively, and they share a common command-line parser library in
      CmdLineParser.  The flags related to modes (--makde, --interactive
      etc.) are now private to the front end: in fact private to Main
      itself, for now.
      d1c1b7d0
  33. 31 Jan, 2005 1 commit
  34. 22 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-22 12:06:13 by simonpj] · d7c402a3
      simonpj authored
      ----------------------------------------
           New Core invariant: keep case alternatives in sorted order
      	----------------------------------------
      
      We now keep the alternatives of a Case in the Core language in sorted
      order.  Sorted, that is,
      	by constructor tag	for DataAlt
      	by literal		for LitAlt
      
      The main reason is that it makes matching and equality testing more robust.
      But in fact some lines of code vanished from SimplUtils.mkAlts.
      
      
      WARNING: no change to interface file formats, but you'll need to recompile
      your libraries so that they generate interface files that respect the
      invariant.
      d7c402a3
  35. 30 Sep, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-09-30 10:35:15 by simonpj] · 23f40f0e
      simonpj authored
      ------------------------------------
      	Add Generalised Algebraic Data Types
      	------------------------------------
      
      This rather big commit adds support for GADTs.  For example,
      
          data Term a where
       	  Lit :: Int -> Term Int
      	  App :: Term (a->b) -> Term a -> Term b
      	  If  :: Term Bool -> Term a -> Term a
      	  ..etc..
      
          eval :: Term a -> a
          eval (Lit i) = i
          eval (App a b) = eval a (eval b)
          eval (If p q r) | eval p    = eval q
          		    | otherwise = eval r
      
      
      Lots and lots of of related changes throughout the compiler to make
      this fit nicely.
      
      One important change, only loosely related to GADTs, is that skolem
      constants in the typechecker are genuinely immutable and constant, so
      we often get better error messages from the type checker.  See
      TcType.TcTyVarDetails.
      
      There's a new module types/Unify.lhs, which has purely-functional
      unification and matching for Type. This is used both in the typechecker
      (for type refinement of GADTs) and in Core Lint (also for type refinement).
      23f40f0e
  36. 09 Oct, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-10-09 11:58:39 by simonpj] · 98688c6e
      simonpj authored
      -------------------------
      		GHC heart/lung transplant
      		-------------------------
      
      This major commit changes the way that GHC deals with importing
      types and functions defined in other modules, during renaming and
      typechecking.  On the way I've changed or cleaned up numerous other
      things, including many that I probably fail to mention here.
      
      Major benefit: GHC should suck in many fewer interface files when
      compiling (esp with -O).  (You can see this with -ddump-rn-stats.)
      
      It's also some 1500 lines of code shorter than before.
      
      **	So expect bugs!  I can do a 3-stage bootstrap, and run
      **	the test suite, but you may be doing stuff I havn't tested.
      ** 	Don't update if you are relying on a working HEAD.
      
      
      In particular, (a) External Core and (b) GHCi are very little tested.
      
      	But please, please DO test this version!
      
      
      	------------------------
      		Big things
      	------------------------
      
      Interface files, version control, and importing declarations
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      * There is a totally new data type for stuff that lives in interface files:
      	Original names			IfaceType.IfaceExtName
      	Types				IfaceType.IfaceType
      	Declarations (type,class,id)	IfaceSyn.IfaceDecl
      	Unfoldings			IfaceSyn.IfaceExpr
        (Previously we used HsSyn for type/class decls, and UfExpr for unfoldings.)
        The new data types are in iface/IfaceType and iface/IfaceSyn.  They are
        all instances of Binary, so they can be written into interface files.
        Previous engronkulation concering the binary instance of RdrName has
        gone away -- RdrName is not an instance of Binary any more.  Nor does
        Binary.lhs need to know about the ``current module'' which it used to,
        which made it specialised to GHC.
      
        A good feature of this is that the type checker for source code doesn't
        need to worry about the possibility that we might be typechecking interface
        file stuff.  Nor does it need to do renaming; we can typecheck direct from
        IfaceSyn, saving a whole pass (module TcIface)
      
      * Stuff from interface files is sucked in *lazily*, rather than being eagerly
        sucked in by the renamer. Instead, we use unsafeInterleaveIO to capture
        a thunk for the unfolding of an imported function (say).  If that unfolding
        is every pulled on, TcIface will scramble over the unfolding, which may
        in turn pull in the interface files of things mentioned in the unfolding.
      
        The External Package State is held in a mutable variable so that it
        can be side-effected by this lazy-sucking-in process (which may happen
        way later, e.g. when the simplifier runs).   In effect, the EPS is a kind
        of lazy memo table, filled in as we suck things in.  Or you could think
        of it as a global symbol table, populated on demand.
      
      * This lazy sucking is very cool, but it can lead to truly awful bugs. The
        intent is that updates to the symbol table happen atomically, but very bad
        things happen if you read the variable for the table, and then force a
        thunk which updates the table.  Updates can get lost that way. I regret
        this subtlety.
      
        One example of the way it showed up is that the top level of TidyPgm
        (which updates the global name cache) to be much more disciplined about
        those updates, since TidyPgm may itself force thunks which allocate new
        names.
      
      * Version numbering in interface files has changed completely, fixing
        one major bug with ghc --make.  Previously, the version of A.f changed
        only if A.f's type and unfolding was textually different.  That missed
        changes to things that A.f's unfolding mentions; which was fixed by
        eagerly sucking in all of those things, and listing them in the module's
        usage list.  But that didn't work with --make, because they might have
        been already sucked in.
      
        Now, A.f's version changes if anything reachable from A.f (via interface
        files) changes.  A module with unchanged source code needs recompiling
        only if the versions of any of its free variables changes. [This isn't
        quite right for dictionary functions and rules, which aren't mentioned
        explicitly in the source.  There are extensive comments in module MkIface,
        where all version-handling stuff is done.]
      
      * We don't need equality on HsDecls any more (because they aren't used in
        interface files).  Instead we have a specialised equality for IfaceSyn
        (eqIfDecl etc), which uses IfaceEq instead of Bool as its result type.
        See notes in IfaceSyn.
      
      * The horrid bit of the renamer that tried to predict what instance decls
        would be needed has gone entirely.  Instead, the type checker simply
        sucks in whatever instance decls it needs, when it needs them.  Easy!
      
        Similarly, no need for 'implicitModuleFVs' and 'implicitTemplateHaskellFVs'
        etc.  Hooray!
      
      
      Types and type checking
      ~~~~~~~~~~~~~~~~~~~~~~~
      * Kind-checking of types is far far tidier (new module TcHsTypes replaces
        the badly-named TcMonoType).  Strangely, this was one of my
        original goals, because the kind check for types is the Right Place to
        do type splicing, but it just didn't fit there before.
      
      * There's a new representation for newtypes in TypeRep.lhs.  Previously
        they were represented using "SourceTypes" which was a funny compromise.
        Now they have their own constructor in the Type datatype.  SourceType
        has turned back into PredType, which is what it used to be.
      
      * Instance decl overlap checking done lazily.  Consider
      	instance C Int b
      	instance C a Int
        These were rejected before as overlapping, because when seeking
        (C Int Int) one couldn't tell which to use.  But there's no problem when
        seeking (C Bool Int); it can only be the second.
      
        So instead of checking for overlap when adding a new instance declaration,
        we check for overlap when looking up an Inst.  If we find more than one
        matching instance, we see if any of the candidates dominates the others
        (in the sense of being a substitution instance of all the others);
        and only if not do we report an error.
      
      
      
      	------------------------
      	     Medium things
      	------------------------
      
      * The TcRn monad is generalised a bit further.  It's now based on utils/IOEnv.lhs,
        the IO monad with an environment.  The desugarer uses the monad too,
        so that anything it needs can get faulted in nicely.
      
      * Reduce the number of wired-in things; in particular Word and Integer
        are no longer wired in.  The latter required HsLit.HsInteger to get a
        Type argument.  The 'derivable type classes' data types (:+:, :*: etc)
        are not wired in any more either (see stuff about derivable type classes
        below).
      
      * The PersistentComilerState is now held in a mutable variable
        in the HscEnv.  Previously (a) it was passed to and then returned by
        many top-level functions, which was painful; (b) it was invariably
        accompanied by the HscEnv.  This change tidies up top-level plumbing
        without changing anything important.
      
      * Derivable type classes are treated much more like 'deriving' clauses.
        Previously, the Ids for the to/from functions lived inside the TyCon,
        but now the TyCon simply records their existence (with a simple boolean).
        Anyone who wants to use them must look them up in the environment.
      
        This in turn makes it easy to generate the to/from functions (done
        in types/Generics) using HsSyn (like TcGenDeriv for ordinary derivings)
        instead of CoreSyn, which in turn means that (a) we don't have to figure
        out all the type arguments etc; and (b) it'll be type-checked for us.
        Generally, the task of generating the code has become easier, which is
        good for Manuel, who wants to make it more sophisticated.
      
      * A Name now says what its "parent" is. For example, the parent of a data
        constructor is its type constructor; the parent of a class op is its
        class.  This relationship corresponds exactly to the Avail data type;
        there may be other places we can exploit it.  (I made the change so that
        version comparison in interface files would be a bit easier; but in
        fact it tided up other things here and there (see calls to
        Name.nameParent).  For example, the declaration pool, of declararations
        read from interface files, but not yet used, is now keyed only by the 'main'
        name of the declaration, not the subordinate names.
      
      * New types OccEnv and OccSet, with the usual operations.
        OccNames can be efficiently compared, because they have uniques, thanks
        to the hashing implementation of FastStrings.
      
      * The GlobalRdrEnv is now keyed by OccName rather than RdrName.  Not only
        does this halve the size of the env (because we don't need both qualified
        and unqualified versions in the env), but it's also more efficient because
        we can use a UniqFM instead of a FiniteMap.
      
        Consequential changes to Provenance, which has moved to RdrName.
      
      * External Core remains a bit of a hack, as it was before, done with a mixture
        of HsDecls (so that recursiveness and argument variance is still inferred),
        and IfaceExprs (for value declarations).  It's not thoroughly tested.
      
      
      	------------------------
      	     Minor things
      	------------------------
      
      * DataCon fields dcWorkId, dcWrapId combined into a single field
        dcIds, that is explicit about whether the data con is a newtype or not.
        MkId.mkDataConWorkId and mkDataConWrapId are similarly combined into
        MkId.mkDataConIds
      
      * Choosing the boxing strategy is done for *source* type decls only, and
        hence is now in TcTyDecls, not DataCon.
      
      * WiredIn names are distinguished by their n_sort field, not by their location,
        which was rather strange
      
      * Define Maybes.mapCatMaybes :: (a -> Maybe b) -> [a] -> [b]
        and use it here and there
      
      * Much better pretty-printing of interface files (--show-iface)
      
      Many, many other small things.
      
      
      	------------------------
      	     File changes
      	------------------------
      * New iface/ subdirectory
      * Much of RnEnv has moved to iface/IfaceEnv
      * MkIface and BinIface have moved from main/ to iface/
      * types/Variance has been absorbed into typecheck/TcTyDecls
      * RnHiFiles and RnIfaces have vanished entirely.  Their
        work is done by iface/LoadIface
      * hsSyn/HsCore has gone, replaced by iface/IfaceSyn
      * typecheck/TcIfaceSig has gone, replaced by iface/TcIface
      * typecheck/TcMonoType has been renamed to typecheck/TcHsType
      * basicTypes/Var.hi-boot and basicTypes/Generics.hi-boot have gone altogether
      98688c6e
  37. 16 Sep, 2003 1 commit
    • simonmar's avatar
      [project @ 2003-09-16 13:03:37 by simonmar] · 2129fa6f
      simonmar authored
      Legacy Removal
      ~~~~~~~~~~~~~~
      
      The following features have been consigned to the bit bucket:
      
        _ccall_
        _casm_
        ``....''  (lit-lits)
        the CCallable class
        the CReturnable class
      2129fa6f
  38. 12 Feb, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-02-12 15:01:31 by simonpj] · 42b63073
      simonpj authored
      -------------------------------------
        Big upheaval to the way that constructors are named
      	-------------------------------------
      
      This commit enshrines the new story for constructor names.  We could never
      really get External Core to work nicely before, but now it does.
      
      The story is laid out in detail in the Commentary
      	ghc/docs/comm/the-beast/data-types.html
      so I will not repeat it here.
      
      	[Manuel: the commentary isn't being updated, apparently.]
      
      However, the net effect is that in Core and in External Core, contructors look
      like constructors, and the way things are printed is all consistent.
      
      It is a fairly pervasive change (which is why it has been so long postponed),
      but I hope the question is now finally closed.
      
      All the libraries compile etc, and I've run many tests, but doubtless there will
      be some dark corners.
      42b63073