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A real bug in the x86_64 native code gen: nice!

This bug would have been caught by -Wall, and I would have gone though
and Walled this file but I know Ben is hacking on this file quite
heavily and I don't want to create undue conflicts.  Ben: it would be
nice to enable -Wall here when you have time.

 * Fix loading of 64bit floats
 * Put SRT and other read only static data in the .text segment

  * Use BlockIds in branch instructions instead of Imms.
  * Assign FP values returned from C calls to the right regs
  * Fix loading of F32s
  * Add a SPARC version of the FreeRegs map to the linear allcator.

This makes about half the tests in codeGen/should_run work.

This merge does not turn on the new codegen (which only compiles
a select few programs at this point),
but it does introduce some changes to the old code generator.

The high bits:
1. The Rep Swamp patch is finally here.
   The highlight is that the representation of types at the
   machine level has changed.
   Consequently, this patch contains updates across several back ends.
2. The new Stg -> Cmm path is here, although it appears to have a
   fair number of bugs lurking.
3. Many improvements along the CmmCPSZ path, including:
   o stack layout
   o some code for infotables, half of which is right and half wrong
   o proc-point splitting

o Moved BlockId stuff to a new file to avoid module recursion
o Defined stack areas for parameter-passing locations and spill slots
o Part way through replacing copy in and copy out nodes
  - added movement instructions for stack pointer
  - added movement instructions for call and return parameters
    (but not with the proper calling conventions)
o Inserting spills and reloads for proc points is now procpoint-aware
  (it was relying on the presence of a CopyIn node as a proxy for
   procpoint knowledge)
o Changed ZipDataflow to expect AGraphs (instead of being polymorphic in
   the type of graph)

Several changes in this patch, partially bug fixes, partially new code:
o bug fixes in ZipDataflow
   - added some checks to verify that facts converge
   - removed some erroneous checks of convergence on entry nodes
   - added some missing applications of transfer functions
o changed dataflow clients to use ZipDataflow, making ZipDataflow0 obsolete
o eliminated DFA monad (no need for separate analysis and rewriting monads with ZipDataflow)
o started stack layout changes
   - no longer generating CopyIn and CopyOut nodes (not yet fully expunged though)
   - still not using proper calling conventions
o simple new optimizations:
   - common block elimination
      -- have not yet tried to move the Adams opt out of CmmProcPointZ
   - block concatenation
o piped optimization fuel up to the HscEnv
   - can be limited by a command-line flag
   - not tested, and probably not yet properly used by clients
o added unique supply to FuelMonad, also lifted unique supply to DFMonad

If the value is > 2^63 then we need to work out its value mod 2pi,
and apply the operation to that instead.

C-- no longer has 'hints'; to guide parameter passing, it
has 'kinds'.  Renamed type constructor, data constructor, and record
fields accordingly

So when the next person compiles the Sparc NCG it should fail more
obviously at compile time rather than panicing at runtime.
Plus one obvious fix for LocalReg gaining an extra param
Missing bits of Sparc NCG:
  * genSwitch for generating jump tables. This is the most tricky one.
  * ALLOCATABLE_REGS_INTEGER and ALLOCATABLE_REGS_DOUBLE just requires
    finding and verifying the values. The nearby comment describes how.
  * isRegRegMove and mkRegRegMoveInstr. Sparc uses Or for int move, check
    what this is supposed to do for single and double float types.
  * regDotColor. Probably just copy the ppc impl.

Split off a FastBool module, to avoid a circular import with Panic

This allows the instance of UserOfLocalRegs to be within Haskell98, and IMHO
 makes the code a little cleaner generally.
This is one small (though tedious) step towards making GHC's code more
 portable...

The old ones caused lots of
    unknown scattered relocation type 4
errors. Patch from Chris Kuklewicz.

Fixes building with -Werror (i.e. validate) and GHC < 6.6

binutils <2.17 can't generate PC64 relocations for x86_64. Hence we
emit only 32 bit PC relative offsets, and artifically stick a zero in
front of them to make them 64 bit (see PprMach.sh ppr_item in
pprDataItem). This works as long as the offset is <32bit AND it's
positive. This is not the case for offsets in jump tables, they are
all negative. This hack sign extends them with a MOVSXL instruction
into the dead index register, then adding the properly sign extended
offset to the jump table base label giving the correct target address
for the following jump.

I've renamed a number of type and data constructors within Cmm so that
the names used in the compiler may more closely reflect the C--
specification 2.1.  I've done a bit of other renaming as well.
Highlights:

  CmmFormal and CmmActual now bear a CmmKind (which for now is a
                                              MachHint as before)
  CmmFormals = [CmmFormal] and CmmActuals = [CmmActual]
  
  suitable changes have been made to both code and nonterminals in the
  Cmm parser (which is as yet untested)

  For reasons I don't understand, parts of the code generator use a
  sequence of 'formal parameters' with no C-- kinds.  For these we now
  have the types
    type CmmFormalWithoutKind   = LocalReg
    type CmmFormalsWithoutKinds = [CmmFormalWithoutKind]

  A great many appearances of (Tau, MachHint) have been simplified to
  the appropriate CmmFormal or CmmActual, though I'm sure there are
  more opportunities.

  Kind and its data constructors are now renamed to
     data GCKind = GCKindPtr | GCKindNonPtr 
  to avoid confusion with the Kind used in the type checker and with CmmKind.

Finally, in a somewhat unrelated bit (and in honor of Simon PJ, who
thought of the name), the Whalley/Davidson 'transaction limit' is now
called 'OptimizationFuel' with the net effect that there are no longer
two unrelated uses of the abbreviation 'tx'.

The type parameter to a C-- procedure now represents a control-flow
graph, not a single instruction.  The newtype ListGraph preserves the 
current representation while enabling other representations and a
sensible way of prettyprinting.  Except for a few changes in the
prettyprinter the new compiler binary should be bit-for-bit identical
to the old.

Older GHCs can't parse OPTIONS_GHC.
This also changes the URL referenced for the -w options from
WorkingConventions#Warnings to CodingStyle#Warnings for the compiler
modules.