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When they existed, they were getting included in the includes_H_FILES
variable (as it uses wildcard to find all header files). But the
.depends files for the programs that generate the headers depend on
$(includes_H_FILES), so the .depends files looked out-of-date once the
headers had been created. This caused unnecessary make reinvocations.

So now we put them in dist* directories, where they ought to be anyway.

With Windows 7 in a vitrual box VM on OS X, some very odd things happen
with dates and time stamps when SSHing into cygwin. e.g. here the
"Change" time is in the past:

$ date; touch foo; stat foo
Fri Dec  2 16:58:07 GMTST 2011
  File: `foo'
  Size: 0               Blocks: 0          IO Block: 65536  regular
empty file
Device: 540aba0bh/1409989131d   Inode: 562949953592977  Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     ian)   Gid: (  513/    None)
Access: 2011-12-02 16:58:07.414457900 +0000
Modify: 2011-12-02 16:58:07.414457900 +0000
Change: 2011-12-02 16:58:03.495141800 +0000
 Birth: 2011-12-02 16:57:57.731469900 +0000

And if we copy such a file, then the copy is older (as determined by the
"Modify" time) than the original:

$ date; touch foo; stat foo; cp foo bar; stat bar
Fri Dec  2 16:59:10 GMTST 2011
  File: `foo'
  Size: 0               Blocks: 0          IO Block: 65536  regular
empty file
Device: 540aba0bh/1409989131d   Inode: 1407374883725128  Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     ian)   Gid: (  513/    None)
Access: 2011-12-02 16:59:10.118457900 +0000
Modify: 2011-12-02 16:59:10.118457900 +0000
Change: 2011-12-02 16:59:06.189477700 +0000
 Birth: 2011-12-02 16:57:57.731469900 +0000
  File: `bar'
  Size: 0               Blocks: 0          IO Block: 65536  regular
empty file
Device: 540aba0bh/1409989131d   Inode: 281474976882512  Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     ian)   Gid: (  513/    None)
Access: 2011-12-02 16:59:06.394555800 +0000
Modify: 2011-12-02 16:59:06.394555800 +0000
Change: 2011-12-02 16:59:06.395532400 +0000
 Birth: 2011-12-02 16:58:40.921899600 +0000

This means that make thinks that things are out of date when it
shouldn't, so reinvokes itself repeatedly until the MAKE_RESTARTS
infinite-recursion test triggers.

The touchy program, like most other programs, creates files with both
Modify and Change in the past, which is still a little odd, but is
consistent, so doesn't break make.

The parallel GC was using setContextSwitches() to stop all the other
threads, which sets the context_switch flag on every Capability.  That
had the side effect of causing every Capability to also switch
threads, and since GCs can be much more frequent than context
switches, this increased the context switch frequency.  When context
switches are expensive (because the switch is between two bound
threads or a bound and unbound thread), the difference is quite
noticeable.

The fix is to have a separate flag to indicate that a Capability
should stop and return to the scheduler, but not switch threads.  I've
called this the "interrupt" flag.

Spotted by gdb's malloc debugger while I was looking for something else.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

When getting options from basicTypes/RdrName.lhs, we were seeing
text like "-- |\n-- ...\n" in the buffer, and lexer then recognises
"-- |\n-- ..." as a complete ITdocCommentNext token, with the end of
the buffer not reached.

Next time round, when we get more input into the buffer, it started
"\n-- * 'Var.Var': see", so the lexer gave us an ITdocSection token.

However, getOptions' only knew about ITdocCommentNext, and so it
stopped at that point, and didn't see the pragmas further down the file.
This caused the build to fail due to -fwarn-tabs not being turned off.

But actually, we don't really want the haddock docs at this point, so
now we just unset Opt_Haddock in getOptionsFromFile.

I tried this out on the panic we're currently getting for #3103:

ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.3.20111128 for x86_64-unknown-linux):
        tcIfaceGlobal (local): not found:
    base:GHC.Word.W#{d 6w}
    [(32R, Type constructor `base:GHC.Word.Word{tc 32R}'),
     (r6O, Identifier `base:GHC.Word.$fNumWord{v r6O}'),
     (r6P, Identifier `base:GHC.Word.$fEqWord{v r6P}'),
     (r6Q, Identifier `base:GHC.Word.$fNumWord1{v r6Q}'),
     (r6R, Identifier `base:GHC.Word.$fNumWord2{v r6R}'),
     (r6S, Data constructor `base:GHC.Word.W#{d r6S}'),
     (r6U, Identifier `base:GHC.Word.W#{v r6U}'),
     (r75, Identifier `base:GHC.Word.$fNumWord_$csignum{v r75}'),
     (r76, Identifier `base:GHC.Word.$fEqWord_$c/={v r76}'),
     (r77, Identifier `base:GHC.Word.$fEqWord_$c=={v r77}')]
{ Main.main
   GHC.defaultErrorHandler
    GHC.runGhc
     GhcMonad.>>=
      GhcMonad.>>=.\
       Main.main'
        Main.doMake
         GhcMake.load
          GhcMake.load2
           GhcMake.upsweep
            GhcMake.upsweep.upsweep'
             GhcMake.reTypecheckLoop
              GhcMake.typecheckLoop
               GhcMake.typecheckLoop.\
                TcRnMonad.initIfaceCheck
                 TcRnMonad.initTcRnIf
                  IOEnv.runIOEnv
                   IOEnv.thenM
                    IOEnv.thenM.\
                     TcIface.typecheckIface
                      TcIface.typecheckIface.\
                       LoadIface.loadDecls
                        LoadIface.loadDecl
                         TcIface.tcIfaceDecl
                          TcIface.tc_iface_decl
                           TcIface.tcIdInfo
                            MonadUtils.foldlM
                             TcIface.tcIdInfo.tcPrag
                              TcIface.tcUnfolding
                               TcIface.tcPragExpr
                                TcIface.tcIfaceExpr
                                 TcIface.tcIfaceAlt
                                  TcIface.tcIfaceDataCon }

 - add getCCSOf# :: a -> State# s -> (# State# s, Addr# #)
   (returns the CCS attached to the supplied object)

 - remove traceCcs# (obsoleted by getCCSOf#)

 - rename getCCCS# to getCurrentCCS#

We now put the before and after filenames into a tree structure,
which vastly improves performance when simulating the delete
commands.

We were generating them from the tcg_tcs field of the TcGblEnv,
but that goes badly wrong when there are top-level Template
Haskell splices, because the tcg_tcs field grows successively.
If we generate record-selector binds for all the TyCons in the
accumulated list, we generate them multiple times for TyCons
earlier in the program.  This what was happening in Trac #5665:
  data T = T { x :: Int }
  $(f 4)  -- Top level splice
  ..more code..
Here the record selector bindings for T were being generated
twice.

Better instead to generate the record-selector bindings in
TcTyClsDecls, right where the new TyCons are being declared (as indeed
they were some time ago).  This pushed me into doing some refactoring:
instead of returning the record bindings, tcTyAndClassDecls adds them
to the tcg_binds field of the TcGblEnv.  I think the result is a bit
nicer, and it has the additional merit of working.

Returns a pointer to the current cost-centre stack when profiling,
NULL otherwise.

This means that both time and heap profiling work for parallel
programs.  Main internal changes:

  - CCCS is no longer a global variable; it is now another
    pseudo-register in the StgRegTable struct.  Thus every
    Capability has its own CCCS.

  - There is a new built-in CCS called "IDLE", which records ticks for
    Capabilities in the idle state.  If you profile a single-threaded
    program with +RTS -N2, you'll see about 50% of time in "IDLE".

  - There is appropriate locking in rts/Profiling.c to protect the
    shared cost-centre-stack data structures.

This patch does enough to get it working, I have cut one big corner:
the cost-centre-stack data structure is still shared amongst all
Capabilities, which means that multiple Capabilities will race when
updating the "allocations" and "entries" fields of a CCS.  Not only
does this give unpredictable results, but it runs very slowly due to
cache line bouncing.

It is strongly recommended that you use -fno-prof-count-entries to
disable the "entries" count when profiling parallel programs. (I shall
add a note to this effect to the docs).

This field was doing nothing.  I think it originally appeared in a
very old incarnation of the new code generator.

This is a vital wibble to:
 f7cf3dcd * Be a bit less gung-ho in exprIsConApp_maybe

that evVarPred.cc_id must be equal to ctPred
needs no longer be true.

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.

Details:
isReflCo is no longer reliable for detection of no-rewriting/flattening
since we are using cached reflexivity solved goals. Introduced a boolean
flag in the flattener for this purpose, instead.

Adding commentary, and fixing a knot-tie related bug.

Commentary only.

1) Stopped rewriting and caching solveds in the inerts because
profiling showed that a lot of time was spent on rewriting
already solved goals.

2) Optimisations in zonkEvBinds for common-case
evidence bindings generated from the constraint solver.

3) Now solved goals cache their evidence terms, so that we can more
aggressively optimize Refl coercions during constraint solving.
This patch also includes a rewrite of rewriteInertEqsFromInertEq
which greatly improves its efficiency.