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  - Attach a SrcSpan to every CostCentre.  This had the side effect
    that CostCentres that used to be merged because they had the same
    name are now considered distinct; so I had to add a Unique to
    CostCentre to give them distinct object-code symbols.

  - New flag: -fprof-auto-calls.  This flag adds an automatic SCC to
    every call site (application, to be precise).  This is typically
    more useful for call stacks than annotating whole functions.

Various tidy-ups at the same time: removed unused NoCostCentre
constructor, and refactored a bit in Coverage.lhs.

The call stack we get from traceStack now looks like this:

Stack trace:
  Main.CAF (<entire-module>)
  Main.main.xs (callstack002.hs:18:12-24)
  Main.map (callstack002.hs:13:12-16)
  Main.map.go (callstack002.hs:15:21-34)
  Main.map.go (callstack002.hs:15:21-23)
  Main.f (callstack002.hs:10:7-43)

In GHC, this provides an easy way to call a C function via a C wrapper.
This is important when the function is really defined by CPP.

Requires the new CApiFFI extension.

Not documented yet, as it's still an experimental feature at this stage.

This improves compile times slightly.

LLVM doesn't support the OS X system assembler anymore so we must use
their assembler through clang. Also improved error messages when various
LLVM tools can't be run.

-ddump-* files are put in the given directory.

-outputdir also sets the dumpdir.

I did a bit of refactoring (of course) at the same time.
See the discussion in Trac #5587.  Most of the real change
is in CoreArity.

This big patch implements a kind-polymorphic core for GHC. The current
implementation focuses on making sure that all kind-monomorphic programs still
work in the new core; it is not yet guaranteed that kind-polymorphic programs
(using the new -XPolyKinds flag) will work.

For more information, see http://haskell.org/haskellwiki/GHC/Kinds

Now included:
    - all language flags
    - all filename-related flags (-i, -osuf, -hidir etc.)
    - all CPP-related flags (-I, -D, -U)

This means ghci now correctly picks up the package flags
for tab completion.

User visible changes
====================

Profilng
--------

Flags renamed (the old ones are still accepted for now):

  OLD            NEW
  ---------      ------------
  -auto-all      -fprof-auto
  -auto          -fprof-exported
  -caf-all       -fprof-cafs

New flags:

  -fprof-auto              Annotates all bindings (not just top-level
                           ones) with SCCs

  -fprof-top               Annotates just top-level bindings with SCCs

  -fprof-exported          Annotates just exported bindings with SCCs

  -fprof-no-count-entries  Do not maintain entry counts when profiling
                           (can make profiled code go faster; useful with
                           heap profiling where entry counts are not used)

Cost-centre stacks have a new semantics, which should in most cases
result in more useful and intuitive profiles.  If you find this not to
be the case, please let me know.  This is the area where I have been
experimenting most, and the current solution is probably not the
final version, however it does address all the outstanding bugs and
seems to be better than GHC 7.2.

Stack traces
------------

+RTS -xc now gives more information.  If the exception originates from
a CAF (as is common, because GHC tends to lift exceptions out to the
top-level), then the RTS walks up the stack and reports the stack in
the enclosing update frame(s).

Result: +RTS -xc is much more useful now - but you still have to
compile for profiling to get it.  I've played around a little with
adding 'head []' to GHC itself, and +RTS -xc does pinpoint the problem
quite accurately.

I plan to add more facilities for stack tracing (e.g. in GHCi) in the
future.

Coverage (HPC)
--------------

 * derived instances are now coloured yellow if they weren't used
 * likewise record field names
 * entry counts are more accurate (hpc --fun-entry-count)
 * tab width is now correct (markup was previously off in source with
   tabs)

Internal changes
================

In Core, the Note constructor has been replaced by

        Tick (Tickish b) (Expr b)

which is used to represent all the kinds of source annotation we
support: profiling SCCs, HPC ticks, and GHCi breakpoints.

Depending on the properties of the Tickish, different transformations
apply to Tick.  See CoreUtils.mkTick for details.

Tickets
=======

This commit closes the following tickets, test cases to follow:

  - Close #2552: not a bug, but the behaviour is now more intuitive
    (test is T2552)

  - Close #680 (test is T680)

  - Close #1531 (test is result001)

  - Close #949 (test is T949)

  - Close #2466: test case has bitrotted (doesn't compile against current
    version of vector-space package)

Conflicts:

	compiler/main/DynFlags.hs
	compiler/main/HscMain.lhs

Conflicts:

	compiler/main/DynFlags.hs
	compiler/main/HscMain.lhs

This reverts commit bb0eb57e.

This reverts commit 4e2121f4.

Now need to import constructors for Foreign.C.Types types

This allows the extension (which is on by default) to be turned off,
which gets us a small step closer to replacing Haskell98 records with
something better.

This addresses the rare cases where the simplifier diverges
(see the above ticket).  We were already counting how many simplifier
steps were taking place, but with no limit.  This patch adds a limit;
at which point we halt compilation, and print out useful stats. The
stats show what is begin inlined, and how often, which points you
directly to the problem.  The limit is set based on the size of the
program.

Instead of halting compilation, we could instead just inhibit
inlining, which would let compilation of the module complete. This is
a bit harder to implement, and it's likely to mean that you unrolled
the function 1143 times and then ran out of ticks; you probably don't
want to complete parsing on this highly-unrolled program.

Flags: -dsimpl-tick-factor=N.  Default is 100 (percent).
       A bigger number increases the allowed maximum tick count.

Basically as documented in http://hackage.haskell.org/trac/ghc/wiki/KindFact,
this patch adds a new kind Constraint such that:

  Show :: * -> Constraint
  (?x::Int) :: Constraint
  (Int ~ a) :: Constraint

And you can write *any* type with kind Constraint to the left of (=>):
even if that type is a type synonym, type variable, indexed type or so on.

The following (somewhat related) changes are also made:
 1. We now box equality evidence. This is required because we want
    to give (Int ~ a) the *lifted* kind Constraint
 2. For similar reasons, implicit parameters can now only be of
    a lifted kind. (?x::Int#) => ty is now ruled out
 3. Implicit parameter constraints are now allowed in superclasses
    and instance contexts (this just falls out as OK with the new
    constraint solver)

Internally the following major changes were made:
 1. There is now no PredTy in the Type data type. Instead
    GHC checks the kind of a type to figure out if it is a predicate
 2. There is now no AClass TyThing: we represent classes as TyThings
    just as a ATyCon (classes had TyCons anyway)
 3. What used to be (~) is now pretty-printed as (~#). The box
    constructor EqBox :: (a ~# b) -> (a ~ b)
 4. The type LCoercion is used internally in the constraint solver
    and type checker to represent coercions with free variables
    of type (a ~ b) rather than (a ~# b)

Allows you to turn off loading/storing the GHCi command history from/to
the ~/.ghc/ghci_history file.