GitLab

If these modules use UniqFM then we get a stack overflow when compiling
modules that use fundeps. I haven't tracked down the actual cause.

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.

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

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.

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.

GC dead code and export list entries.

CPR control

1.  Remove -fno-cpr, add -fcpr-off which is a simple static flag
    for switching the new CPR analysis off altogether.
    (The "-fno" machinery is rather complicated.)

2.  Rejig SimplCore a little so that the "old strictness analyser"
    runs both the old strictness analyser and the old CPR analyser,
    which makes it more like the new strictness/CPR analyser.

    (How much longer we keep the old strictness/CPR analyser in the
    compiler at all I don't know.  It's just for comparision purposes
    when we write the paper.)

Heal the head

Dont print (Prod [AAA]) same as (Poly Abs)

Add seqDemand, seqDemands, seqDmdType and seqStrictSig.

--------------------------------------
	Yet another cut at the DmdAnal domains
	--------------------------------------

This version of the domain for demand analysis was developed
in discussion with Peter Sestoft, so I think it might at last
be more or less right!

Our idea is mentally to separate
	strictness analysis
from
	absence and boxity analysis

Then we combine them back into a single domain.  The latter
is all you see in the compiler (the Demand type, as before)
but we understand it better now.

Move defer from NewDemand to DmdAnal

- Pet peeve removal / code tidyup, replaced various sub-optimal
  uses of 'length' with something a bit better, i.e., replaced
  the following patterns

   *  length as `cmpOp` length bs
   *  length as `cmpOp` val   -- incl. uses where val == 1 and val == 0
   *  {take,drop,splitAt} (length as) bs
   *  length [ () | pat <- as ]

  with uses of misc Util functions.

  I'd be surprised if there's a noticeable reduction in running
  times as a result of these changes, but every little bit helps.

  [ The changes have been tested wrt testsuite/ - I'm seeing a couple
    of unexpected breakages coming from CorePrep, but I'm currently
    assuming that these are due to other recent changes. ]

- compMan/CompManager.lhs: restored 4.08 compilability + some code
  cleanup.

None of these changes are HEADworthy.

Fix two minor bugs in DmdAnal, and add comments.
The bugs were both in dmdTransform, the dataConId case

  * The test for saturation should be against call_depth
    not agaainst (length ds).

  * The arg_ds computation for k=Keep should be
    with 'both' not 'lub'.

Heal the HEAD

Add comments, and nuke strictness info in CoreTidy if totally boring

Make isStrictDmd give the right answer

------------------------
	Fix the demand analyser
	------------------------

A spiffy new domain for demands, and definitions for lub/both
which are actually monotonic.   Quite a bit of related jiggling
around.

One of the original motivations was to do with functions like:

	sum n []     = n
	sum n (x:xs) = sum (n+x) xs

Even though n is returned boxed from the first case, we don't want
to get strictness
	S(L)V -> T
because that means we pass the box for n, and that is TERRIBLE.
So the new version errs on the side of unboxing, more like the forwards
analyser, and only passes the box if it is *definitely* needed, rather
than if it *may* be needed.

Change pretty-print of DmdType slightly

A major demand-analyser fix, which made it say something was
absent when it wasn't at all.  Here's the comment from the
Case equation of dmdAnal.

	-- Figure out whether the case binder is used, and use
	-- that to set the keepity of the demand.  This is utterly essential.
	-- Consider	f x = case x of y { (a,b) -> k y a }
	-- If we just take scrut_demand = U(L,A), then we won't pass x to the
	-- worker, so the worker will rebuild
	--	x = (a, absent-error)
	-- and that'll crash.

Keep the printed stuff for Demand and DmdResult separate, else
we can get confused when parsing a strictness signature.  For
example, previously

	LX

could have been parsed as	L  -> X
or as				LX -> T

Urk!  I've taken the simple path of making DmdResults print in
lower case.  Thus

	Lx 	means	L  -> x
	LX	means	LX -> t

---------------------------------
	Switch to the new demand analyser
	---------------------------------

This commit makes the new demand analyser the main beast,
with the old strictness analyser as a backup.  When
DEBUG is on, the old strictness analyser is run too, and the
results compared.

WARNING: this isn't thorougly tested yet, so expect glitches.
Delay updating for a few days if the HEAD is mission critical
for you.

But do try it out.  I'm away for 2.5 weeks from Thursday, so
it would be good to shake out any glaring bugs before then.

Next cut at the demand analyser

--------------------------------
	First cut at the demand analyser
	--------------------------------

This demand analyser is intended to replace the strictness/absence
analyser, and the CPR analyser.

This commit adds it to the compiler, but in an entirely non-invasive
way.

	If you build the compiler without -DDEBUG,
	you won't get it at all.

	If you build the compiler with -DDEBUG,
	you'll get the demand analyser, but the existing
	strictness analyser etc are still there.  All the
	demand analyser does is to compare its output with
	the existing stuff and report differences.

There's no cross-module stuff for demand info yet.

The strictness/demand info is put the IdInfo as
	newStrictnessInfo
	newDemandInfo

Eventually we'll remove the old ones.

Simon