[commit: ghc] master: Make 'SPECIALISE instance' work again (1ed0409)

[Simon Peyton Jones]

Repository : http://darcs.haskell.org/ghc.git/

On branch  : master

https://github.com/ghc/ghc/commit/1ed0409010afeaa318676e351b833aea659bf93a

>---------------------------------------------------------------

commit 1ed0409010afeaa318676e351b833aea659bf93a
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Thu May 30 12:08:39 2013 +0100

    Make 'SPECIALISE instance' work again
    
    This is a long-standing regression (Trac #7797), which meant that in
    particular the Eq [Char] instance does not get specialised.
    (The *methods* do, but the dictionary itself doesn't.)  So when you
    call a function
         f :: Eq a => blah
    on a string type (ie a=[Char]), 7.6 passes a dictionary of un-specialised
    methods.
    
    This only matters when calling an overloaded function from a
    specialised context, but that does matter in some programs.  I
    remember (though I cannot find the details) that Nick Frisby discovered
    this to be the source of some pretty solid performanc regresisons.
    
    Anyway it works now. The key change is that a DFunUnfolding now takes
    a form that is both simpler than before (the DFunArg type is eliminated)
    and more general:
    
    data Unfolding
      = ...
      | DFunUnfolding {     -- The Unfolding of a DFunId
        			-- See Note [DFun unfoldings]
          		  	--     df = /\a1..am. \d1..dn. MkD t1 .. tk
                            --                                 (op1 a1..am d1..dn)
         		      	--     	    	      	       	   (op2 a1..am d1..dn)
            df_bndrs :: [Var],      -- The bound variables [a1..m],[d1..dn]
            df_con   :: DataCon,    -- The dictionary data constructor (never a newtype datacon)
            df_args  :: [CoreExpr]  -- Args of the data con: types, superclasses and methods,
        }                           -- in positional order
    
    That in turn allowed me to re-enable the DFunUnfolding specialisation in
    DsBinds.  Lots of details here in TcInstDcls:
    	  Note [SPECIALISE instance pragmas]
    
    I also did some refactoring, in particular to pass the InScopeSet to
    exprIsConApp_maybe (which in turn means it has to go to a RuleFun).
    
    NB: Interface file format has changed!

 compiler/basicTypes/MkId.lhs                   |   8 +-
 compiler/coreSyn/CoreFVs.lhs                   |  33 +++--
 compiler/coreSyn/CoreSubst.lhs                 |  65 +++++----
 compiler/coreSyn/CoreSyn.lhs                   |  39 ++----
 compiler/coreSyn/CoreTidy.lhs                  |   7 +-
 compiler/coreSyn/CoreUnfold.lhs                |  11 +-
 compiler/coreSyn/PprCore.lhs                   |  10 +-
 compiler/deSugar/DsBinds.lhs                   |  39 +++---
 compiler/iface/BinIface.hs                     |  15 +--
 compiler/iface/IfaceSyn.lhs                    |   9 +-
 compiler/iface/MkIface.lhs                     |   4 +-
 compiler/iface/TcIface.lhs                     |  10 +-
 compiler/main/TidyPgm.lhs                      |   3 +-
 compiler/prelude/PrelRules.lhs                 | 180 +++++++------------------
 compiler/simplCore/OccurAnal.lhs               |   2 +-
 compiler/simplCore/SimplUtils.lhs              |  12 +-
 compiler/simplCore/Simplify.lhs                |  12 +-
 compiler/specialise/Rules.lhs                  |  76 +++++------
 compiler/specialise/Specialise.lhs             |  20 ++-
 compiler/typecheck/TcInstDcls.lhs              | 120 ++++++++++-------
 compiler/vectorise/Vectorise/Generic/PADict.hs |  24 ++--
 21 files changed, 316 insertions(+), 383 deletions(-)


Diff suppressed because of size. To see it, use:

    git show 1ed0409010afeaa318676e351b833aea659bf93a