GitLab

--------------------------------------
	Finally get rid of tcAddImportedIdInfo
	--------------------------------------

TcEnv.tcAddImportedIdInfo is a notorious source of space leaks.
Simon M got rid of the need for it on default methods.
This commit gets rid of the need for it for dictionary function Ids,
and finally nukes the beast altogether. Hurrah!

The change really involves putting tcInterfaceSigs *before*
tcInstDecls1, so that any imported DFunIds are in the typechecker's
environment before we get to tcInstDecls.

Add missing files for Rank-N commit

----------------------
	Implement Rank-N types
	----------------------

This commit implements the full glory of Rank-N types, using
the Odersky/Laufer approach described in their paper
	"Putting type annotations to work"

In fact, I've had to adapt their approach to deal with the
full glory of Haskell (including pattern matching, and the
scoped-type-variable extension).  However, the result is:

* There is no restriction to rank-2 types.  You can nest forall's
  as deep as you like in a type.  For example, you can write a type
  like
	p :: ((forall a. Eq a => a->a) -> Int) -> Int
  This is a rank-3 type, illegal in GHC 5.02

* When matching types, GHC uses the cunning Odersky/Laufer coercion
  rules.  For example, suppose we have
	q :: (forall c. Ord c => c->c) -> Int
  Then, is this well typed?
	x :: Int
	x = p q
  Yes, it is, but GHC has to generate the right coercion.  Here's
  what it looks like with all the big lambdas and dictionaries put in:

	x = p (\ f :: (forall a. Eq a => a->a) ->
		 q (/\c \d::Ord c -> f c (eqFromOrd d)))

  where eqFromOrd selects the Eq superclass dictionary from the Ord
  dicationary:		eqFromOrd :: Ord a -> Eq a


* You can use polymorphic types in pattern type signatures.  For
  example:

	f (g :: forall a. a->a) = (g 'c', g True)

  (Previously, pattern type signatures had to be monotypes.)

* The basic rule for using rank-N types is that you must specify
  a type signature for every binder that you want to have a type
  scheme (as opposed to a plain monotype) as its type.

  However, you don't need to give the type signature on the
  binder (as I did above in the defn for f).  You can give it
  in a separate type signature, thus:

	f :: (forall a. a->a) -> (Char,Bool)
	f g = (g 'c', g True)

  GHC will push the external type signature inwards, and use
  that information to decorate the binders as it comes across them.
  I don't have a *precise* specification of this process, but I
  think it is obvious enough in practice.

* In a type synonym you can use rank-N types too.  For example,
  you can write

	type IdFun = forall a. a->a

	f :: IdFun -> (Char,Bool)
	f g = (g 'c', g True)

  As always, type synonyms must always occur saturated; GHC
  expands them before it does anything else.  (Still, GHC goes
  to some trouble to keep them unexpanded in error message.)


The main plan is as before.  The main typechecker for expressions,
tcExpr, takes an "expected type" as its argument.  This greatly
improves error messages.  The new feature is that when this
"expected type" (going down) meets an "actual type" (coming up)
we use the new subsumption function
	TcUnify.tcSub
which checks that the actual type can be coerced into the
expected type (and produces a coercion function to demonstrate).

The main new chunk of code is TcUnify.tcSub.  The unifier itself
is unchanged, but it has moved from TcMType into TcUnify.  Also
checkSigTyVars has moved from TcMonoType into TcUnify.
Result: the new module, TcUnify, contains all stuff relevant
to subsumption and unification.

Unfortunately, there is now an inevitable loop between TcUnify
and TcSimplify, but that's just too bad (a simple TcUnify.hi-boot
file).


All of this doesn't come entirely for free.  Here's the typechecker
line count (INCLUDING comments)
	Before	16,551
	After	17,116

Added a new section that describes how GHC defines its hardwired knowledge
about primitives and special prelude definitions.

Tidyup - only declare&use half-a-dozen prof-only global variables
when PROFILING.

Retainer/LDV changes.

The recent prof-related commit forgot to include RtsFlags.h, methinks.
But, modulo trivia, I'm reasonably sure that this commit mirrors
whatever mods that unchecked-in file contains.

extend the scope of the doNothing() macro; can now be used in Stg headers

Put spaces round %, in preparation for splittable name supplies

unbreak tcModule.

Use (DefMeth Name) rather than (DefMeth Id) in ClassOpItem.  This not
only eliminates a space leak, because Names generally hold on to much
less stuff than Ids, but also turns out to be a minor cleanup.

Replace a lazy pattern match in tcGetInstLoc with a strict one (fixes
a space leak).

Adorn various constructor fields with strictness annotations - this
fixes at least one space leak, in the mi_usages field of a ModIface.

Collect up _scc_ expressions on the right hand side of a closure
definition and attach them directly to the closure using PushCC-type
cost centres, so that the allocation of the closure gets attributed to
the right place.

Fix a long-standing bug in the cost attribution of cost-center stacks.
The problem case is this:

	let z = _scc_ "z" f x
	in ... z ...

previously we were attributing the cost of allocating the closure 'z'
to the enclosing cost center stack (CCCS), when it should really be
attributed to "z":CCCS.  The effects are particularly visible with
retainer profiling, because the closure retaining 'f' and 'x' would
show up with the wrong CCS attached.

To fix this, we need a new form of CCS representation internally:
'PushCC CostCentre CostCentreStack' which subsumes (and therefore
replaces) SingletonCCS.  SingletonCCS is now represented by 'PushCC cc
NoCCS'.

The CCS argument to SET_HDR may now be an arbitrary expression, such
as PushCostCentre(CCCS,foo_cc), as may be the argument to CCS_ALLOC().
So we combine SET_HDR and CCS_ALLOC into a single macro, SET_HDR_, to
avoid repeated calls to PushCostCentre().

Call LDV_ENTER() on entry to a constructor in profiling mode.

Call LDV_ENTER() on entry to a thunk or function in profiling mode.

Add
	ldvEnter :: Code

for LDV profiling: it records that the closure pointed to by R1 has
just been entered.

We don't need to consider Hp as a volatile register across C calls; it
is already saved by the CALLER_SAVES_SYSTEM macro.

Fix compilation problems with Stats.c in the !DEBUG case.

Omit GC and SYSTEM from the cost centre summary at the top of the profile.

Add rts_getThreadId to the Linker's built in symbol table

Retainer Profiling / Lag-drag-void profiling.

This is mostly work by Sungwoo Park, who spent a summer internship at
MSR Cambridge this year implementing these two types of heap profiling
in GHC.

Relative to Sungwoo's original work, I've made some improvements to
the code:

   - it's now possible to apply constraints to retainer and LDV profiles
     in the same way as we do for other types of heap profile (eg.
     +RTS -hc{foo,bar} -hR -RTS gives you a retainer profiling considering
     only closures with cost centres 'foo' and 'bar').

   - the heap-profile timer implementation is cleaned up.

   - heap profiling no longer has to be run in a two-space heap.

   - general cleanup of the code and application of the SDM C coding
     style guidelines.

Profiling will be a little slower and require more space than before,
mainly because closures have an extra header word to support either
retainer profiling or LDV profiling (you can't do both at the same
time).

We've used the new profiling tools on GHC itself, with moderate
success.  Fixes for some space leaks in GHC to follow...

Inlining pragma buglet

Update this document.  Some of the implementation problems can be
solved in a cleaner way, and the document was confused about the
problems caused by slop in the heap (it's only a problem when
traversing the dead heap, not the live heap).

initialize_virtual_timer: Robustified win32 version; don't
assume that the minimal resolution is one millisec, consult
the underlying impl via timeGetDevCaps().

StablePtr indexes/counts are no longer weighted (i.e., sync wrt Stable.{c,h} changes)

#ifdef protect generated config.h file.

Turn the weighted reference count in a StablePtr into a simple counter
in the stable ptr table.  We never made use of the weighted count, and
it caused problems when making many StablePtrs to the same object.

In the future we could remove the reference counting altogether and
just make a new StablePtr each time, rather than attempting to use an
existing one.  This would save on the hash table lookup at creation
time.

Have prototypes and implementation of prel_PrelHandle_{write,read}() match
up with the stated Haskell FFI type in PrelHandle.hs, i.e., the size
parameter is a CInt, not an Int.

getTimes (win32): Win9x OSes don't provide per-process timing data, so
GetProcessTimes() doesn't do anything interesting. So, resort to using
system-time instead to measure user/process time iff running under Win9x.
(the precision is not as good, deltas were ~6 millisecs when testing
on a Win98 box, but it's better than nothing).

This change should make profiling on Win9x boxes finally work.

Nuke #include of MachDeps.h - nothing in there that cannot be
(better) gotten from the in-tree config.h

This is the only (last?) use of MachDeps.h, so if anyone won't argue
for its continued existence, I'll nuke it sometime soon.

Print to stdout instead of stderr.  I'm pretty ambivalent about this,
but Sungwoo Park made the changes as part of his retainer profiling
work so he must have had a good reason for it at the time...

Add constant-folding rules for Float# and Double#

If the configure script determined that the build-tree version of happy
is to be used, descend into happy/ and build it, if needs be.

- change the interpretation of FPTOOLS_TOP_ABS, it is now the UNIXy path.
  For Win32, it is of the form <drive>:<path> where '/' is the directory
  separator. Prior to this commit, the directory separator was '\'.
- for the (only) place we need to have a platform-native representation
  of FPTOOLS_TOP_ABS, use FPTOOLS_TOP_ABS_PLATFORM.

Tidy up imports

Improve error msg

--------------------------------------
	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.

Added a new section that covers lexing and parsing.

if IS_CBITS_LIB is YES: Extend SRC_HS2HS_OPTS in the same way that SRC_CC_OPTS is