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-------------------------------------
Remove all vestiges of usage analysis
-------------------------------------
This commit removes a large blob of usage-analysis-related code, almost
all of which was commented out.
Sadly, it doesn't look as if Keith is going to have enough time to polish it
up, and in any case the actual performance benefits (so far as we can measure
them) turned out to be pretty modest (a few percent).
So, with regret, I'm chopping it all out. It's still there in the repository
if anyone wants go hack on it. And Tobias Gedell at Chalmers is implementing
a different analysis, via External Core.
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- 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.
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--------------------
A major hygiene pass
--------------------
1. The main change here is to
Move what was the "IdFlavour" out of IdInfo,
and into the varDetails field of a Var
It was a mess before, because the flavour was a permanent attribute
of an Id, whereas the rest of the IdInfo was ephemeral. It's
all much tidier now.
Main places to look:
Var.lhs Defn of VarDetails
IdInfo.lhs Defn of GlobalIdDetails
The main remaining infelicity is that SpecPragmaIds are right down
in Var.lhs, which seems unduly built-in for such an ephemeral thing.
But that is no worse than before.
2. Tidy up the HscMain story a little. Move mkModDetails from MkIface
into CoreTidy (where it belongs more nicely)
This was partly forced by (1) above, because I didn't want to make
DictFun Ids into a separate kind of Id (which is how it was before).
Not having them separate means we have to keep a list of them right
through, rather than pull them out of the bindings at the end.
3. Add NameEnv as a separate module (to join NameSet).
4. Remove unnecessary {-# SOURCE #-} imports from FieldLabel.
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I finally got tired of not having
splitTyConApp
tyConAppTyCon
tyConAppArgs
(Previously we called splitTyConApp_maybe,
but it's a pain in the neck.)
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1. Outputable.PprStyle now carries a bit more information
In particular, the printing style tells whether to print
a name in unqualified form. This used to be embedded in
a Name, but since Names now outlive a single compilation unit,
that's no longer appropriate.
So now the print-unqualified predicate is passed in the printing
style, not embedded in the Name.
2. I tidied up HscMain a little. Many of the showPass messages
have migraged into the repective pass drivers
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This commit completes the merge of compiler part
of the HEAD with the before-ghci-branch to
before-ghci-branch-merged.
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Tons of stuff for the mornings work
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Fix simplifier stuff.
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Do the begin-pass/end-pass stuff like the other core passes
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remove unused imports
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~~~~~~~~~~~~
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[!]
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Adjust treatment of rules in SimplCore to enable a Core pass to alter
them if necessary. Use tricks to ensure that the common case (no change)
is still efficient.
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GHC has instance amnesia again, so a bunch of funny
`import Ppr{Core,Type} ()? had to be added. Sorry,
but I need a bootstrapping GHC.
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This utterly gigantic commit is what I've been up to in background
mode in the last couple of months. Originally the main goal
was to get rid of Con (staturated constant applications)
in the CoreExpr type, but one thing led to another, and I kept
postponing actually committing. Sorry.
Simon, 23 March 2000
I've tested it pretty thoroughly, but doubtless things will break.
Here are the highlights
* Con is gone; the CoreExpr type is simpler
* NoRepLits have gone
* Better usage info in interface files => less recompilation
* Result type signatures work
* CCall primop is tidied up
* Constant folding now done by Rules
* Lots of hackery in the simplifier
* Improvements in CPR and strictness analysis
Many bug fixes including
* Sergey's DoCon compiles OK; no loop in the strictness analyser
* Volker Wysk's programs don't crash the CPR analyser
I have not done much on measuring compilation times and binary sizes;
they could have got worse. I think performance has got significantly
better, though, in most cases.
Removing the Con form of Core expressions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The big thing is that
For every constructor C there are now *two* Ids:
C is the constructor's *wrapper*. It evaluates and unboxes arguments
before calling $wC. It has a perfectly ordinary top-level defn
in the module defining the data type.
$wC is the constructor's *worker*. It is like a primop that simply
allocates and builds the constructor value. Its arguments are the
actual representation arguments of the constructor.
Its type may be different to C, because:
- useless dict args are dropped
- strict args may be flattened
For every primop P there is *one* Id, its (curried) Id
Neither contructor worker Id nor the primop Id have a defminition anywhere.
Instead they are saturated during the core-to-STG pass, and the code generator
generates code for them directly. The STG language still has saturated
primops and constructor applications.
* The Const type disappears, along with Const.lhs. The literal part
of Const.lhs reappears as Literal.lhs. Much tidying up in here,
to bring all the range checking into this one module.
* I got rid of NoRep literals entirely. They just seem to be too much trouble.
* Because Con's don't exist any more, the funny C { args } syntax
disappears from inteface files.
Parsing
~~~~~~~
* Result type signatures now work
f :: Int -> Int = \x -> x
-- The Int->Int is the type of f
g x y :: Int = x+y
-- The Int is the type of the result of (g x y)
Recompilation checking and make
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* The .hi file for a modules is not touched if it doesn't change. (It used to
be touched regardless, forcing a chain of recompilations.) The penalty for this
is that we record exported things just as if they were mentioned in the body of
the module. And the penalty for that is that we may recompile a module when
the only things that have changed are the things it is passing on without using.
But it seems like a good trade.
* -recomp is on by default
Foreign declarations
~~~~~~~~~~~~~~~~~~~~
* If you say
foreign export zoo :: Int -> IO Int
then you get a C produre called 'zoo', not 'zzoo' as before.
I've also added a check that complains if you export (or import) a C
procedure whose name isn't legal C.
Code generation and labels
~~~~~~~~~~~~~~~~~~~~~~~~~~
* Now that constructor workers and wrappers have distinct names, there's
no need to have a Foo_static_closure and a Foo_closure for constructor Foo.
I nuked the entire StaticClosure story. This has effects in some of
the RTS headers (i.e. s/static_closure/closure/g)
Rules, constant folding
~~~~~~~~~~~~~~~~~~~~~~~
* Constant folding becomes just another rewrite rule, attached to the Id for the
PrimOp. To achieve this, there's a new form of Rule, a BuiltinRule (see CoreSyn.lhs).
The prelude rules are in prelude/PrelRules.lhs, while simplCore/ConFold.lhs has gone.
* Appending of constant strings now works, using fold/build fusion, plus
the rewrite rule
unpack "foo" c (unpack "baz" c n) = unpack "foobaz" c n
Implemented in PrelRules.lhs
* The CCall primop is tidied up quite a bit. There is now a data type CCall,
defined in PrimOp, that packages up the info needed for a particular CCall.
There is a new Id for each new ccall, with an big "occurrence name"
{__ccall "foo" gc Int# -> Int#}
In interface files, this is parsed as a single Id, which is what it is, really.
Miscellaneous
~~~~~~~~~~~~~
* There were numerous places where the host compiler's
minInt/maxInt was being used as the target machine's minInt/maxInt.
I nuked all of these; everything is localised to inIntRange and inWordRange,
in Literal.lhs
* Desugaring record updates was broken: it didn't generate correct matches when
used withe records with fancy unboxing etc. It now uses matchWrapper.
* Significant tidying up in codeGen/SMRep.lhs
* Add __word, __word64, __int64 terminals to signal the obvious types
in interface files. Add the ability to print word values in hex into
C code.
* PrimOp.lhs is no longer part of a loop. Remove PrimOp.hi-boot*
Types
~~~~~
* isProductTyCon no longer returns False for recursive products, nor
for unboxed products; you have to test for these separately.
There's no reason not to do CPR for recursive product types, for example.
Ditto splitProductType_maybe.
Simplification
~~~~~~~~~~~~~~~
* New -fno-case-of-case flag for the simplifier. We use this in the first run
of the simplifier, where it helps to stop messing up expressions that
the (subsequent) full laziness pass would otherwise find float out.
It's much more effective than previous half-baked hacks in inlining.
Actually, it turned out that there were three places in Simplify.lhs that
needed to know use this flag.
* Make the float-in pass push duplicatable bindings into the branches of
a case expression, in the hope that we never have to allocate them.
(see FloatIn.sepBindsByDropPoint)
* Arrange that top-level bottoming Ids get a NOINLINE pragma
This reduced gratuitous inlining of error messages.
But arrange that such things still get w/w'd.
* Arrange that a strict argument position is regarded as an 'interesting'
context, so that if we see
foldr k z (g x)
then we'll be inclined to inline g; this can expose a build.
* There was a missing case in CoreUtils.exprEtaExpandArity that meant
we were missing some obvious cases for eta expansion
Also improve the code when handling applications.
* Make record selectors (identifiable by their IdFlavour) into "cheap" operations.
[The change is a 2-liner in CoreUtils.exprIsCheap]
This means that record selection may be inlined into function bodies, which
greatly improves the arities of overloaded functions.
* Make a cleaner job of inlining "lone variables". There was some distributed
cunning, but I've centralised it all now in SimplUtils.analyseCont, which
analyses the context of a call to decide whether it is "interesting".
* Don't specialise very small functions in Specialise.specDefn
It's better to inline it. Rather like the worker/wrapper case.
* Be just a little more aggressive when floating out of let rhss.
See comments with Simplify.wantToExpose
A small change with an occasional big effect.
* Make the inline-size computation think that
case x of I# x -> ...
is *free*.
CPR analysis
~~~~~~~~~~~~
* Fix what was essentially a bug in CPR analysis. Consider
letrec f x = let g y = let ... in f e1
in
if ... then (a,b) else g x
g has the CPR property if f does; so when generating the final annotated
RHS for f, we must use an envt in which f is bound to its final abstract
value. This wasn't happening. Instead, f was given the CPR tag but g
wasn't; but of course the w/w pass gives rotten results in that case!!
(Because f's CPR-ness relied on g's.)
On they way I tidied up the code in CprAnalyse. It's quite a bit shorter.
The fact that some data constructors return a constructed product shows
up in their CPR info (MkId.mkDataConId) not in CprAnalyse.lhs
Strictness analysis and worker/wrapper
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* BIG THING: pass in the demand to StrictAnal.saExpr. This affects situations
like
f (let x = e1 in (x,x))
where f turns out to have strictness u(SS), say. In this case we can
mark x as demanded, and use a case expression for it.
The situation before is that we didn't "know" that there is the u(SS)
demand on the argument, so we simply computed that the body of the let
expression is lazy in x, and marked x as lazily-demanded. Then even after
f was w/w'd we got
let x = e1 in case (x,x) of (a,b) -> $wf a b
and hence
let x = e1 in $wf a b
I found a much more complicated situation in spectral/sphere/Main.shade,
which improved quite a bit with this change.
* Moved the StrictnessInfo type from IdInfo to Demand. It's the logical
place for it, and helps avoid module loops
* Do worker/wrapper for coerces even if the arity is zero. Thus:
stdout = coerce Handle (..blurg..)
==>
wibble = (...blurg...)
stdout = coerce Handle wibble
This is good because I found places where we were saying
case coerce t stdout of { MVar a ->
...
case coerce t stdout of { MVar b ->
...
and the redundant case wasn't getting eliminated because of the coerce.
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A regrettably-gigantic commit that puts in place what Simon PJ
has been up to for the last month or so, on and off.
The basic idea was to restore unfoldings to *occurrences* of
variables without introducing a space leak. I wanted to make
sure things improved relative to 4.04, and that proved depressingly
hard. On the way I discovered several quite serious bugs in the
simplifier.
Here's a summary of what's gone on.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* No commas between for-alls in RULES. This makes the for-alls have
the same syntax as in types.
* Arrange that simplConArgs works in one less pass than before.
This exposed a bug: a bogus call to completeBeta.
* Add a top-level flag in CoreUnfolding, used in callSiteInline
* Extend w/w to use etaExpandArity, so it does eta/coerce expansion
* Implement inline phases. The meaning of the inline pragmas is
described in CoreUnfold.lhs. You can say things like
{#- INLINE 2 build #-}
to mean "inline build in phase 2"
* Don't float anything out of an INLINE.
Don't float things to top level unless they also escape a value lambda.
[see comments with SetLevels.lvlMFE
Without at least one of these changes, I found that
{-# INLINE concat #-}
concat = __inline (/\a -> foldr (++) [])
was getting floated to
concat = __inline( /\a -> lvl a )
lvl = ...inlined version of foldr...
Subsequently I found that not floating constants out of an INLINE
gave really bad code like
__inline (let x = e in \y -> ...)
so I now let things float out of INLINE
* Implement the "reverse-mapping" idea for CSE; actually it turned out to be easier
to implement it in SetLevels, and may benefit full laziness too.
* It's a good idea to inline inRange. Consider
index (l,h) i = case inRange (l,h) i of
True -> l+i
False -> error
inRange itself isn't strict in h, but if it't inlined then 'index'
*does* become strict in h. Interesting!
* Big change to the way unfoldings and occurrence info is propagated in the simplifier
The plan is described in Subst.lhs with the Subst type
Occurrence info is now in a separate IdInfo field than user pragmas
* I found that
(coerce T (coerce S (\x.e))) y
didn't simplify in one round. First we get to
(\x.e) y
and only then do the beta. Solution: cancel the coerces in the continuation
* Amazingly, CoreUnfold wasn't counting the cost of a function an application.
* Disable rules in initial simplifier run. Otherwise full laziness
doesn't get a chance to lift out a MFE before a rule (e.g. fusion)
zaps it. queens is a case in point
* Improve float-out stuff significantly. The big change is that if we have
\x -> ... /\a -> ...let p = ..a.. in let q = ...p...
where p's rhs doesn't x, we abstract a from p, so that we can get p past x.
(We did that before.) But we also substitute (p a) for p in q, and then
we can do the same thing for q. (We didn't do that, so q got stuck.)
This is much better. It involves doing a substitution "as we go" in SetLevels,
though.
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Fix use of _unused var for ghc-3.XX.
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Layout fix to uses of ASSERT in do expressions; thanks Kevin for
pointing out the problem.
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This commit makes a start at implementing polymorphic usage
annotations.
* The module Type has now been split into TypeRep, containing the
representation Type(..) and other information for `friends' only,
and Type, providing the public interface to Type. Due to a bug in
the interface-file slurping prior to ghc-4.04, {-# SOURCE #-}
dependencies must unfortunately still refer to TypeRep even though
they are not friends.
* Unfoldings in interface files now print as __U instead of __u.
UpdateInfo now prints as __UA instead of __U.
* A new sort of variables, UVar, in their own namespace, uvName, has
been introduced for usage variables.
* Usage binders __fuall uv have been introduced. Usage annotations
are now __u - ty (used once), __u ! ty (used possibly many times),
__u uv ty (used uv times), where uv is a UVar. __o and __m have
gone. All this still lives only in a TyNote, *for now* (but not for
much longer).
* Variance calculation for TyCons has moved from
typecheck/TcTyClsDecls to types/Variance.
* Usage annotation and inference are now done together in a single
pass. Provision has been made for inferring polymorphic usage
annotations (with __fuall) but this has not yet been implemented.
Watch this space!
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Rescue UsageSP analysis from bit-rot.
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RULES-NOTES
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(this is number 5a of 9 commits to be applied together)
The major purpose of this commit is to introduce usage information
and usage analysis into the compiler, per the paper _Once Upon a
Polymorphic Type_ (Keith Wansbrough and Simon Peyton Jones, POPL'99,
and Glasgow TR-1998-19).
An analysis is provided that annotates a Core program with optimal
usage annotations. This analysis is performed by -fusagesp
(=CoreDoUSPInf), and requires -fusagesp-on (=opt_UsageSPOn). This
latter performs an analysis in tidyCorePgm, immediately before
CoreToStg is done. The driver flag -fusagesp currently provides hsc
with -fusagesp-on, and if -O is on does a single -fusagesp early on
in the Core-to-Core sequence. Please change this as desired.
*NB*: For now, -fusagesp with -O requires -fno-specialise. Sorry.
The flags -ddump-usagesp (=opt_D_dump_usagesp) and -dusagesp-lint
(=opt_DoUSPLinting) (also -dnousagesp-lint to the driver) have been
added and are documented in the User Guide.
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