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--------------------------------------
	Make Template Haskell into the HEAD
	--------------------------------------

This massive commit transfers to the HEAD all the stuff that
Simon and Tim have been doing on Template Haskell.  The
meta-haskell-branch is no more!

WARNING: make sure that you

  * Update your links if you are using link trees.
    Some modules have been added, some have gone away.

  * Do 'make clean' in all library trees.
    The interface file format has changed, and you can
    get strange panics (sadly) if GHC tries to read old interface files:
    e.g.  ghc-5.05: panic! (the `impossible' happened, GHC version 5.05):
	  Binary.get(TyClDecl): ForeignType

  * You need to recompile the rts too; Linker.c has changed


However the libraries are almost unaltered; just a tiny change in
Base, and to the exports in Prelude.


NOTE: so far as TH itself is concerned, expression splices work
fine, but declaration splices are not complete.


		---------------
		The main change
		---------------

The main structural change: renaming and typechecking have to be
interleaved, because we can't rename stuff after a declaration splice
until after we've typechecked the stuff before (and the splice
itself).

* Combine the renamer and typecheker monads into one
	(TcRnMonad, TcRnTypes)
  These two replace TcMonad and RnMonad

* Give them a single 'driver' (TcRnDriver).  This driver
  replaces TcModule.lhs and Rename.lhs

* The haskell-src library package has a module
	Language/Haskell/THSyntax
  which defines the Haskell data type seen by the TH programmer.

* New modules:
	hsSyn/Convert.hs 	converts THSyntax -> HsSyn
	deSugar/DsMeta.hs 	converts HsSyn -> THSyntax

* New module typecheck/TcSplice type-checks Template Haskell splices.

		-------------
		Linking stuff
		-------------

* ByteCodeLink has been split into
	ByteCodeLink	(which links)
	ByteCodeAsm	(which assembles)

* New module ghci/ObjLink is the object-code linker.

* compMan/CmLink is removed entirely (was out of place)
  Ditto CmTypes (which was tiny)

* Linker.c initialises the linker when it is first used (no need to call
  initLinker any more).  Template Haskell makes it harder to know when
  and whether to initialise the linker.


	-------------------------------------
	Gathering the LIE in the type checker
	-------------------------------------

* Instead of explicitly gathering constraints in the LIE
	tcExpr :: RenamedExpr -> TcM (TypecheckedExpr, LIE)
  we now dump the constraints into a mutable varabiable carried
  by the monad, so we get
	tcExpr :: RenamedExpr -> TcM TypecheckedExpr

  Much less clutter in the code, and more efficient too.
  (Originally suggested by Mark Shields.)


		-----------------
		Remove "SysNames"
		-----------------

Because the renamer and the type checker were entirely separate,
we had to carry some rather tiresome implicit binders (or "SysNames")
along inside some of the HsDecl data structures.  They were both
tiresome and fragile.

Now that the typechecker and renamer are more intimately coupled,
we can eliminate SysNames (well, mostly... default methods still
carry something similar).

		-------------
		Clean up HsPat
		-------------

One big clean up is this: instead of having two HsPat types (InPat and
OutPat), they are now combined into one.  This is more consistent with
the way that HsExpr etc is handled; there are some 'Out' constructors
for the type checker output.

So:
	HsPat.InPat	--> HsPat.Pat
	HsPat.OutPat	--> HsPat.Pat
	No 'pat' type parameter in HsExpr, HsBinds, etc

	Constructor patterns are nicer now: they use
		HsPat.HsConDetails
	for the three cases of constructor patterns:
		prefix, infix, and record-bindings

	The *same* data type HsConDetails is used in the type
	declaration of the data type (HsDecls.TyData)

Lots of associated clean-up operations here and there.  Less code.
Everything is wonderful.

In code style, print negative floating point literals in parentheses
to avoid interacting with surrounding syntax.

Fixes SourceForge bug #604849

MERGE TO STABLE

FastString cleanup, stage 1.

The FastString type is no longer a mixture of hashed strings and
literal strings, it contains hashed strings only with O(1) comparison
(except for UnicodeStr, but that will also go away in due course).  To
create a literal instance of FastString, use FSLIT("..").

By far the most common use of the old literal version of FastString
was in the pattern

	  ptext SLIT("...")

this combination still works, although it doesn't go via FastString
any more.  The next stage will be to remove the need to use this
special combination at all, using a RULE.

To convert a FastString into an SDoc, now use 'ftext' instead of
'ptext'.

I've also removed all the FAST_STRING related macros from HsVersions.h
except for SLIT and FSLIT, just use the relevant functions from
FastString instead.

Misc cleanup: remove the iface pretty-printing style, and clean up
bits of StringBuffer that aren't required any more.

Binary Interface Files - stage 1
--------------------------------

This commit changes the default interface file format from text to
binary, in order to improve compilation performace.

To view an interface file, use 'ghc --show-iface Foo.hi'.

utils/Binary.hs is the basic Binary I/O library, based on the nhc98
binary I/O library but much stripped-down and working in terms of
bytes rather than bits, and with some special features for GHC: it
remembers which Module is being emitted to avoid dumping too many
qualified names, and it keeps track of a "dictionary" of FastStrings
so that we don't dump the same FastString more than once into the
binary file.  I'll make a generic version of this for the libraries at
some point.

main/BinIface.hs contains most of the Binary instances.  Some
instances are in the same module as the data type (RdrName, Name,
OccName in particular).  Most instances were generated using a
modified version of DrIFT, which I'll commit later.  However, editing
them by hand isn't hard (certainly easier than modifying
ParseIface.y).

The first thing in a binary interface is the interface version, so
nice error messages will be generated if the binary format changes and
you still have old interfaces lying around.  The version also now
includes the "way" as an extra sanity check.

Other changes
-------------

I don't like the way FastStrings contain both hashed strings (with
O(1) comparison) and literal C strings (with O(n) comparison).  So as
a first step to separating these I made serveral "literal" type
strings into hashed strings.  SLIT() still generates a literal, and
now FSLIT() generates a hashed string.  With DEBUG on, you'll get a
warning if you try to compare any SLIT()s with anything, and the
compiler will fall over if you try to dump any literal C strings into
an interface file (usually indicating a use of SLIT() which should be
FSLIT()).

mkSysLocal no longer re-encodes its FastString argument each time it
is called.

I also fixed the -pgm options so that the argument can now optionally
be separted from the option.

Bugfix: PrelNames declared Names for several comparison primops, eg.
eqCharName, eqIntName etc. but these had different uniques from the
real primop names.  I've moved these to PrimOps and defined them using
mkPrimOpIdName instead, and deleted some for which we don't have real
primops (Manuel: please check that things still work for you after
this change).

----------------
	Division by zero
	----------------

Teach GHC that the division primops can't fail if the divisor
is non-zero.  This can eliminate some thunks in an inner loop.

Amplify comment on mkMachInt a little

Remove the in-range assertions on mkMachInt/mkMachWord.  They clearly
aren't true, because there's nothing stopping you from writing an
out-of-range Int# literal (although that's the only way I can see for
these to arise).

The wider issue is what should be done about out-of-range Int#
literals; I vaguely remember that at some point we disallowed them,
but I can't find anything in the logs.  The case which triggered the
assertion, namely "intToWord# 0xffff0000" would appear to be a
legitimate use for an out-of-range Int# literal though, given that
you can't write Word# literals directly.

How I spent my summer vacation.

Primops
-------

The format of the primops.txt.pp file has been enhanced to allow
(latex-style) primop descriptions to be included.  There is a new flag
to genprimopcode that generates documentation including these
descriptions. A first cut at descriptions of the more interesting
primops has been made, and the file has been reordered a bit.

31-bit words
------------

The front end now can cope with the possibility of 31-bit (or even 30-bit)
Int# and Word# types.  The only current use of this is to generate
external .core files that can be translated into OCAML source files
(OCAML uses a one-bit tag to distinguish integers from pointers).
The only way to get this right now is by hand-defining the preprocessor
symbol WORD_SIZE_IN_BITS, which is normally set automatically from
the familiar WORD_SIZE_IN_BYTES.

Just in case 31-bit words are used, we now have Int32# and Word32# primitive types
and an associated family of operators, paralleling the existing 64-bit
stuff.  Of course, none of the operators actually need to be implemented
in the absence of a 31-bit backend.
There has also been some minor re-jigging of the 32 vs. 64 bit stuff.
See the description at the top of primops.txt.pp file for more details.
Note that, for the first time, the *type* of a primop can now depend
on the target word size.

Also, the family of primops intToInt8#, intToInt16#, etc.
have been renamed narrow8Int#, narrow16Int#, etc., to emphasize
that they work on Int#'s and don't actually convert between types.

Addresses
---------

As another part of coping with the possibility of 31-bit ints,
the addr2Int# and int2Addr# primops are now thoroughly deprecated
(and not even defined in the 31-bit case) and all uses
of them have been removed except from the (deprecated) module
hslibs/lang/Addr

Addr# should now be treated as a proper abstract type, and has these suitable operators:

nullAddr# : Int# -> Addr# (ignores its argument; nullary primops cause problems at various places)
plusAddr# :  Addr# -> Int# -> Addr#
minusAddr : Addr# -> Addr# -> Int#
remAddr# : Addr# -> Int# -> Int#

Obviously, these don't allow completely arbitrary offsets if 31-bit ints are
in use, but they should do for all practical purposes.

It is also still possible to generate an address constant, and there is a built-in rule
that makes use of this to remove the nullAddr# calls.

Misc
----
There is a new compile flag -fno-code that causes GHC to quit after generating .hi files
and .core files (if requested) but before generating STG.

Z-encoded names for tuples have been rationalized; e.g.,
Z3H now means an unboxed 3-tuple, rather than an unboxed
tuple with 3 commas (i.e., a 4-tuple)!

Removed misc. litlits in hslibs/lang

Misc. small changes to external core format.  The external core description
has also been substantially updated, and incorporates the automatically-generated
primop documentation; its in the repository at /papers/ext-core/core.tex.

A little make-system addition to allow passing CPP options to compiler and
library builds.

fix typo in double2IntLit

----------------
	Squash newtypes
	----------------

This commit squashes newtypes and their coerces, from the typechecker
onwards.  The original idea was that the coerces would not get in the
way of optimising transformations, but despite much effort they continue
to do so.   There's no very good reason to retain newtype information
beyond the typechecker, so now we don't.

Main points:

* The post-typechecker suite of Type-manipulating functions is in
types/Type.lhs, as before.   But now there's a new suite in types/TcType.lhs.
The difference is that in the former, newtype are transparent, while in
the latter they are opaque.  The typechecker should only import TcType,
not Type.

* The operations in TcType are all non-monadic, and most of them start with
"tc" (e.g. tcSplitTyConApp).  All the monadic operations (used exclusively
by the typechecker) are in a new module, typecheck/TcMType.lhs

* I've grouped newtypes with predicate types, thus:
	data Type = TyVarTy Tyvar | ....
		  | SourceTy SourceType

	data SourceType = NType TyCon [Type]
			| ClassP Class [Type]
			| IParam Type

[SourceType was called PredType.]  This is a little wierd in some ways,
because NTypes can't occur in qualified types.   However, the idea is that
a SourceType is a type that is opaque to the type checker, but transparent
to the rest of the compiler, and newtypes fit that as do implicit parameters
and dictionaries.

* Recursive newtypes still retain their coreces, exactly as before. If
they were transparent we'd get a recursive type, and that would make
various bits of the compiler diverge (e.g. things which do type comparison).

* I've removed types/Unify.lhs (non-monadic type unifier and matcher),
merging it into TcType.

Ditto typecheck/TcUnify.lhs (monadic unifier), merging it into TcMType.

Add builtin rules for {intToInt,wordToWord}{8,16,32}# applied to literals.

Allow out-of-range character literals to appear in interface-file
unfoldings.  They occasionally pop up in Core.

Improved comment.

Don't duplicate strings semi-willy-nilly.  Literal strings now have a
size dependent on their length.

Move FAST_INT and FAST_BOOL into their own module FastTypes, replacing
the macro definitions in HsVersions.h with real definitions.  Change
most of the names in the process.

Now we don't get bogus imports of GlaExts all over the place, and
-fwarn-unused-imports is less noisy.

Now Char, Char#, StgChar have 31 bits (physically 32).
"foo"# is still an array of bytes.

CharRep represents 32 bits (on a 64-bit arch too). There is also
Int8Rep, used in those places where bytes were originally meant.
readCharArray, indexCharOffAddr etc. still use bytes. Storable and
{I,M}Array use wide Chars.

In future perhaps all sized integers should be primitive types. Then
some usages of indexing primops scattered through the code could
be changed to then-available Int8 ones, and then Char variants of
primops could be made wide (other usages that handle text should use
conversion that will be provided later).

I/O and _ccall_ arguments assume ISO-8859-1. UTF-8 is internally used
for string literals (only).

Z-encoding is ready for Unicode identifiers.

Ranges of intlike and charlike closures are more easily configurable.

I've probably broken nativeGen/MachCode.lhs:chrCode for Alpha but I
don't know the Alpha assembler to fix it (what is zapnot?). Generally
I'm not sure if I've done the NCG changes right.

This commit breaks the binary compatibility (of course).

TODO:
* is* and to{Lower,Upper} in Char (in progress).
* Libraries for text conversion (in design / experiments),
  to be plugged to I/O and a higher level foreign library.
* PackedString.
* StringBuffer and accepting source in encodings other than ISO-8859-1.

Fixed conversion of MachWord to MachInt for large literals. Although
completely untested, I believe this fixes bug #111021.

Simon's Marktoberdorf Commits

1.  Tidy up the renaming story for "system binders", such as
dictionary functions, default methods, constructor workers etc.  These
are now documented in HsDecls.  The main effect of the change, apart
from tidying up, is to make the *type-checker* (instead of the
renamer) generate names for dict-funs and default-methods.  This is
good because Sergei's generic-class stuff generates new classes at
typecheck time.


2.  Fix the CSE pass so it does not require the no-shadowing invariant.
Keith discovered that the simplifier occasionally returns a result
with shadowing.  After much fiddling around (which has improved the
code in the simplifier a bit) I found that it is nearly impossible to
arrange that it really does do no-shadowing.  So I gave up and fixed
the CSE pass (which is the only one to rely on it) instead.


3. Fix a performance bug in the simplifier.  The change is in
SimplUtils.interestingArg.  It computes whether an argment should 
be considered "interesting"; if a function is applied to an interesting
argument, we are more likely to inline that function.
Consider this case
	let x = 3 in f x
The 'x' argument was considered "uninteresting" for a silly reason.
Since x only occurs once, it was unconditionally substituted, but
interestingArg didn't take account of that case.  Now it does.

I also made interestingArg a bit more liberal.  Let's see if we
get too much inlining now.


4.  In the occurrence analyser, we were choosing a bad loop breaker.
Here's the comment that's now in OccurAnal.reOrderRec

    score ((bndr, rhs), _, _)
	| exprIsTrivial rhs 	   = 3	-- Practically certain to be inlined
		-- Used to have also: && not (isExportedId bndr)
		-- But I found this sometimes cost an extra iteration when we have
		--	rec { d = (a,b); a = ...df...; b = ...df...; df = d }
		-- where df is the exported dictionary. Then df makes a really
		-- bad choice for loop breaker

I also increased the score for bindings with a non-functional type, so that
dictionaries have a better chance of getting inlined early


5. Add a hash code to the InScopeSet (and make it properly abstract)
This should make uniqAway a lot more robust.  Simple experiments suggest
that uniqAway no longer gets into the long iteration chains that it used
to.


6.  Fix a bug in the inliner that made the simplifier tend to get into
a loop where it would keep iterating ("4 iterations, bailing out" message).
In SimplUtils.mkRhsTyLam we float bindings out past a big lambda, thus:
	x = /\ b -> let g = \x -> f x x
		    in E
becomes
	g* = /\a -> \x -> f x x
	x = /\ b -> let g = g* b in E
	
It's essential that we don't simply inling g* back into the RHS of g,
else we will be back to square 1.  The inliner is meant not to do this
because there's no benefit to the inlining, but the size calculation
was a little off in CoreUnfold.


7.  In SetLevels we were bogus-ly building a Subst with an empty in-scope
set, so a WARNING popped up when compiling some modules.  (knights/ChessSetList
was the example that tickled it.)  Now in fact the warning wasn't an error,
but the Right Thing to do is to carry down a proper Subst in SetLevels, so
that is what I have now done.  It is very little more expensive.

Hash MachLabel, too

New form of literal: MachLabel, for addresses of labels.  Used by
foreign label instead of MachLitLit now.

Real lit-lits now cause the NCG to panic.

Also: removed CLitLit from AbsCSyn; it was only used in one place for
a purpose it shouldn't have been used for in the first place.

Don't use addr2Integer for large integral literals anymore, use a
Horner schema with numbers in the Int range instead. This improves
constant folding, so e.g.  (0x87654321 :: Word32) is evaluated at
compile time now. In theory we can completely say Good-bye to
addr2Integer, but for the time being it's still there. Feel free to
nuke it...  >:-)

Backed out previous commit, the change was at the completely wrong place.
*please merge*

Prefix litlits with "__litlit" in interface files.
*please merge*

~~~~~~~~~~~~
		Apr/May 2000
		~~~~~~~~~~~~

This is a pretty big commit!  It adds stuff I've been working on
over the last month or so.  DO NOT MERGE IT WITH 4.07!

Interface file formats have changed a little; you'll need
to make clean before remaking.

						Simon PJ

Recompilation checking
~~~~~~~~~~~~~~~~~~~~~~
Substantial improvement in recompilation checking.  The version management
is now entirely internal to GHC.  ghc-iface.lprl is dead!

The trick is to generate the new interface file in two steps:
  - first convert Types etc to HsTypes etc, and thereby
	build a new ParsedIface
  - then compare against the parsed (but not renamed) version of the old
	interface file
Doing this meant adding code to convert *to* HsSyn things, and to
compare HsSyn things for equality.  That is the main tedious bit.

Another improvement is that we now track version info for
fixities and rules, which was missing before.


Interface file reading
~~~~~~~~~~~~~~~~~~~~~~
Make interface files reading more robust.
  * If the old interface file is unreadable, don't fail. [bug fix]

  * If the old interface file mentions interfaces
    that are unreadable, don't fail. [bug fix]

  * When we can't find the interface file,
    print the directories we are looking in.  [feature]


Type signatures
~~~~~~~~~~~~~~~
  * New flag -ddump-types to print type signatures


Type pruning
~~~~~~~~~~~~
When importing
	data T = T1 A | T2 B | T3 C
it seems excessive to import the types A, B, C as well, unless
the constructors T1, T2 etc are used.  A,B,C might be more types,
and importing them may mean reading more interfaces, and so on.
 So the idea is that the renamer will just import the decl
	data T
unless one of the constructors is used.  This turns out to be quite
easy to implement.  The downside is that we must make sure the
constructors are always available if they are really needed, so
I regard this as an experimental feature.


Elimininate ThinAir names
~~~~~~~~~~~~~~~~~~~~~~~~~
Eliminate ThinAir.lhs and all its works.  It was always a hack, and now
the desugarer carries around an environment I think we can nuke ThinAir
altogether.

As part of this, I had to move all the Prelude RdrName defns from PrelInfo
to PrelMods --- so I renamed PrelMods as PrelNames.

I also had to move the builtinRules so that they are injected by the renamer
(rather than appearing out of the blue in SimplCore).  This is if anything simpler.

Miscellaneous
~~~~~~~~~~~~~
* Tidy up the data types involved in Rules

* Eliminate RnEnv.better_provenance; use Name.hasBetterProv instead

* Add Unique.hasKey :: Uniquable a => a -> Unique -> Bool
  It's useful in a lot of places

* Fix a bug in interface file parsing for __U[!]

Added rules for constant folding with the folloging ops:
WordQuotOp, WordRemOp, AndOp, OrOp, XorOp, Int2AddrOp, Addr2IntOp,
Float2IntOp, DoubleNegOp, Double2IntOp, Double2FloatOp, Float2DoubleOp

Add missing Literal.lhs

Move 4.01 onto the main trunk.

MachInt64 and MachWord64 added; avoid gratuitous range checking on MachInts

The Great Multi-Parameter Type Classes Merge.

Notes from Simon (abridged):

* Multi-parameter type classes are fully implemented.
* Error messages from the type checker should be noticeably improved
* Warnings for unused bindings (-fwarn-unused-names)
* many other minor bug fixes.

Internally there are the following changes

* Removal of Haskell 1.2 compatibility.
* Dramatic clean-up of the PprStyle stuff.
* The type Type has been substantially changed.
* The dictionary for each class is represented by a new
  data type for that purpose, rather than by a tuple.

Updated imports

2.04 changes

Major update to more-or-less 2.02

Pragmas in interface files added

SLPJ 1.3 changes through 96/06/25

SLPJ changes through 960604

simonpj/sansom/partain/dnt 1.3 compiler stuff through 96/03/18

Initial revision