the hot path contained a call to

    v `elemUnVarSet` (neighbors g v)

and creating the set of neighbors just to check if `v` is inside
accounted for half the allocations of the test case of #15164.

By introducing a non-allocating function `hasLoopAt` for this we shave
off half the allocations. This brings the total cost of Call Arity down
to 20% of time and 23% of allocations, according to a profiled run. Not
amazing, but still much better.

Differential Revision: https://phabricator.haskell.org/D4718

This reverts commit 1cdc14f9.

This is causing non-deterministic testsuite output.

This patch adds a check for type families to the instance-decl
termination check.  See Note [Type families in instance contexts]
and Trac #15172.

A Derived CFunEqCan does not "own" its FlatMetaTv (fmv), and should not
update it.  But one caller (canCFunEqCan) was failing to satisfy the
precondition to dischargeFmv, which led to a crash (Trac #15170).

I fixed this by making dischargeFmv handle Deriveds (to avoid forcing
each caller to do so separately).

NB: this does not completely fix the original #15170 bug, but I'll
explain that on the ticket.  The test case for this patch is actually
the program in comment:1.

Trac #15164 showed that it sometimes really matters to share
sub-proofs when solving constraints.  Without it, we can get
exponentialy bad behaviour.

Fortunately, it's easily solved.
Note [Shortcut try_solve_from_instance] explains.

I did some minor assocaited refactoring.

Austin Seipp authored 6 years ago and Ben Gamari committed 6 years ago

See `Note [Recompute abi-depends]` for more information.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

Test Plan: `./validate`

Reviewers: bgamari, ezyang

Reviewed By: bgamari

Subscribers: tdammers, juhp, carter, alexbiehl, shlevy, cocreature,
rwbarton, thomie

GHC Trac Issues: #14381

Differential Revision: https://phabricator.haskell.org/D4159

Ben Gamari authored 6 years ago and Ben Gamari committed 6 years ago

unpackClosure#'s behavior and type has changed. This caused a CPP guard
in the new ghc-heap package to fail when bootstrapping with GHC 8.4.

Test Plan: Validate bootstrapping with GHC 8.4

Reviewers: RyanGlScott

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4716

patrickdoc authored 6 years ago and Ben Gamari committed 6 years ago

This pulls parts of Joachim Breitner's ghc-heap-view library inside GHC.
The bits added are the C hooks into the RTS and a basic Haskell wrapper
to these C hooks. The main reason for these to be added to GHC proper
is that the code needs to be kept in sync with the closure types
defined by the RTS. It is expected that the version of HeapView shipped
with GHC will always work with that version of GHC and that extra
functionality can be layered on top with a library like ghc-heap-view
distributed via Hackage.

Test Plan: validate

Reviewers: simonmar, hvr, nomeata, austin, Phyx, bgamari, erikd

Reviewed By: bgamari

Subscribers: carter, patrickdoc, tmcgilchrist, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3055

Alp Mestanogullari authored 6 years ago and Ben Gamari committed 6 years ago

This finally gets us to a green ./validate --slow on linux for a ghc
checkout from the beginning of this week, see

  https://circleci.com/gh/ghc/ghc/4739

This is hopefully the final (or second to final) patch to
address #14890.

Test Plan: ./validate --slow

Reviewers: bgamari, hvr, simonmar

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14890

Differential Revision: https://phabricator.haskell.org/D4712

Jack Henahan authored 6 years ago and Ben Gamari committed 6 years ago

Add Foldable and Traversable instances for Data.Monoid.Alt

Signed-off-by: Jack Henahan <jhenahan@me.com>

Reviewers: hvr, bgamari

Reviewed By: bgamari

Subscribers: mpickering, rwbarton, thomie, carter

GHC Trac Issues: #15099

Differential Revision: https://phabricator.haskell.org/D4698

This patch is an easy fix to Trac #15144, which was caused
by accidentally unifying a representational equality in the
unflattener.  (The main code in TcInteract was always careful
not to do so, but I'd missed the test in the unflattener.)

See Note [Do not unify representational equalities]
in TcInteract

Trac #15009 showed that, for Given TyVar/TyVar equalities, we really
want to orient them with the deepest-bound skolem on the left. As it
happens, we also want to do the same for Wanteds, but for a different
reason (more likely to be touchable).  Either way, deepest wins:
see TcUnify Note [Deeper level on the left].

This observation led me to some significant changes:

* A SkolemTv already had a TcLevel, but the level wasn't really being
  used.   Now it is!

* I updated added invariant (SkolInf) to TcType
  Note [TcLevel and untouchable type variables], documenting that
  the level number of all the ic_skols should be the same as the
  ic_tclvl of the implication

* FlatSkolTvs and FlatMetaTvs previously had a dummy level-number of
  zero, which messed the scheme up.   Now they get a level number the
  same way as all other TcTyVars, instead of being a special case.

* To make sure that FlatSkolTvs and FlatMetaTvs are untouchable (which
  was previously done via their magic zero level) isTouchableMetaTyVar
  just tests for those two cases.

* TcUnify.swapOverTyVars is the crucial orientation function; see the
  new Note [TyVar/TyVar orientation].  I completely rewrote this function,
  and it's now much much easier to understand.

I ended up doing some related refactoring, of course

* I noticed that tcImplicitTKBndrsX and tcExplicitTKBndrsX were doing
  a lot of useless work in the case where there are no skolems; I
  added a fast-patch

* Elminate the un-used tcExplicitTKBndrsSig; and thereby get rid of
  the higher-order parameter to tcExpliciTKBndrsX.

* Replace TcHsType.emitTvImplication with TcUnify.checkTvConstraints,
  by analogy with TcUnify.checkConstraints.

* Inline TcUnify.buildImplication into its only call-site in
  TcUnify.checkConstraints

* TcS.buildImplication becomes TcS.CheckConstraintsTcS, with a
  simpler API

* Now that we have NoEvBindsVar we have no need of termEvidenceAllowed;
  nuke the latter, adding Note [No evidence bindings] to TcEvidence.

Happily, both of these issues appear to have been fixed in GHC 8.2.
Let's add regression tests for them to ensure that they stay fixed.

Summary:
There were a number of leaks causing previously loaded modules to be
retained after a new `:load`.  This fixes enough leaks to get the
tests to pass from D4658.

Test Plan: See new tests in D4658

Reviewers: niteria, bgamari, simonpj, erikd

Subscribers: thomie, carter

GHC Trac Issues: #15111

Differential Revision: https://phabricator.haskell.org/D4659

Under certain circumstances, `GeneralizedNewtypeDeriving`
can emit code which uses unboxed tuple types, but if `UnboxedTuples`
wasn't enabled, the error message that GHC gave didn't make it very
clear that it could be worked around by explicitly enabling the
extension. Easily fixed.

Test Plan: make test TEST=T15073

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: simonpj, thomie, carter

GHC Trac Issues: #15073

Differential Revision: https://phabricator.haskell.org/D4620

Fixes #15081.

Test Plan: cd libraries/base && make test TEST="enumNumeric"

Reviewers: hvr, bgamari

Reviewed By: bgamari

Subscribers: dfeuer, simonpj, thomie, carter

GHC Trac Issues: #15081

Differential Revision: https://phabricator.haskell.org/D4650

GHC previously had a handful of special cases for
pretty-printing equalities in a more user-friendly manner, but they
were far from comprehensive (see #15039 for an example of where this
fell apart).

This patch makes the pretty-printing of equalities much more
systematic. I've adopted the approach laid out in
https://ghc.haskell.org/trac/ghc/ticket/15039#comment:4, and updated
`Note [Equality predicates in IfaceType]` accordingly. We are now
more careful to respect the properties of the
`-fprint-explicit-kinds` and `-fprint-equality-relations` flags,
which led to some improvements in error message outputs.

Along the way, I also tweaked the error-reporting machinery not to
print out the type of a typed hole when the type is an unlifted
equality, since it's kind (`TYPE ('TupleRep '[])`) was more
confusing than anything.

Test Plan: make test TEST="T15039a T15039b T15039c T15039d"

Reviewers: simonpj, goldfire, bgamari

Reviewed By: simonpj

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #15039

Differential Revision: https://phabricator.haskell.org/D4696

Summary:
- Previously we would hvae a single big table of pointers per module,
  with a set of bitmaps to reference entries within it. The new
  representation is identical to a static constructor, which is much
  simpler for the GC to traverse, and we get to remove the complicated
  bitmap-traversal code from the GC.

- Rewrite all the code to generate SRTs in CmmBuildInfoTables, and
  document it much better (see Note [SRTs]). This has been something
  I've wanted to do since we moved to the new code generator, I
  finally had the opportunity to finish it while on a transatlantic
  flight recently :)

There are a series of 4 diffs:

1. D4632 (this one), which does the bulk of the changes

2. D4633 which adds support for smaller `CmmLabelDiffOff` constants

3. D4634 which takes advantage of D4632 and D4633 to save a word in
   info tables that have an SRT on x86_64. This is where most of the
   binary size improvement comes from.

4. D4637 which makes a further optimisation to merge some SRTs with
   static FUN closures.  This adds some complexity and the benefits
   are fairly modest, so it's not clear yet whether we should do this.

Results (after (3), on x86_64)

- GHC itself (staticaly linked) is 5.2% smaller

- -1.7% binary sizes in nofib, -2.9% module sizes. Full nofib results: P176

- I measured the overhead of traversing all the static objects in a
  major GC in GHC itself by doing `replicateM_ 1000 performGC` as the
  first thing in `Main.main`.  The new version was 5-10% faster, but
  the results did vary quite a bit.

- I'm not sure if there's a compile-time difference, the results are
  too unreliable.

Test Plan: validate

Reviewers: bgamari, michalt, niteria, simonpj, erikd, osa1

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D4632

Artem Pelenitsyn authored 6 years ago and Ben Gamari committed 6 years ago

Simplifier depends on typechecker in two points: `thNameToGhcName`
(`lookupThName_maybe`, in particular)  and `lookupGlobal`. We want to
cut the ties in two steps.

1. (Presented in this commit), reimplement both functions in a way that
doesn't use typechecker.

2. (Should follow), do code moving: a) `lookupGlobal` should go in some
typechecker-free place; b) `thNameToGhcName` should leave simplifier,
because it is not used there at all (probably, it should be placed
somewhere where `GhcPlugins` can see it -- this is suggested by Joachim
on Trac).

Details
=======

We redesigned lookup interface a bit so that it exposes some
`IO`-equivalents of `Tc`-features in use.

First, `CoreMonad.hs` still calls `lookupGlobal` which is no longer
bound to the typechecker monad, but still resides in `TcEnv.hs` — it
should be moved out of Tc-land at some point (“Phase 2”) in the
future in order to achieve its part of the #14391's goal.

Second, `lookupThName_maybe` is eliminated from `CoreMonad.hs`
completely; this already achieves its part of the goal of #14391. Its
client, though, `thNameToGhcName`, is better to be moved in the future
also, for it is not used in the `CoreMonad.hs` (or anywhere else)
anyway. Joachim suggested “any module reexported by GhcPlugins (or
maybe even that module itself)”.

As a side goal, we removed `initTcForLookup` which was instrumental for
the past version of `lookupGlobal`. This, in turn, called for pushing
some more parts of the lookup interface from the `Tc`-monad to `IO`,
most notably, adding `IO`-version of `lookupOrig` and pushing
`dataConInfoPtrToName` to `IO`. The `lookupOrig` part, in turn,
triggered a slight redesign of name cache updating interface: we now
have both, `updNameCacheIO` and `updNameCacheTc`, both accepting `mod`
and `occ` to force them inside, instead of more error-prone outside
before. But all these hardly have to do anything with #14391, mere
refactoring.

Reviewers: simonpj, nomeata, bgamari, hvr

Reviewed By: simonpj, bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14391

Differential Revision: https://phabricator.haskell.org/D4503

Sebastian Graf authored 6 years ago and Ben Gamari committed 6 years ago

Previously, the `{add,sub}{Int,Word}C#` PrimOps weren't handled
in PrelRules (constant folding and algebraic simplification) at all.
This implements the necessary logic, so that using these primitives
isn't too punishing compared to their well-optimised, overflow-unaware
counterparts.

This is so that using these primitives in `enumFromThenTo @Int` can
be optimized by constant folding, reducing closure sizes.

Reviewers: bgamari, simonpj, hsyl20

Reviewed By: bgamari, simonpj

Subscribers: AndreasK, thomie, carter

GHC Trac Issues: #8763

Differential Revision: https://phabricator.haskell.org/D4605

Ben Gamari authored 6 years ago and Ben Gamari committed 6 years ago

Test Plan: Validate on Windows

Subscribers: thomie, carter

GHC Trac Issues: #14697, #15072

Differential Revision: https://phabricator.haskell.org/D4619

This lead to some rather significant performance regressions.
Specifically,

    bytes allocated value is too high:
        Expected    T5631(normal) bytes allocated: 1106015512 +/-5%
        Lower bound T5631(normal) bytes allocated: 1050714736
        Upper bound T5631(normal) bytes allocated: 1161316288
        Actual      T5631(normal) bytes allocated: 1164953208
        Deviation   T5631(normal) bytes allocated:        5.3 %
    *** unexpected stat test failure for T5631(normal)
    max_bytes_used value is too high:
        Expected    T9630(normal) max_bytes_used: 35324712 +/-15%
        Lower bound T9630(normal) max_bytes_used: 30026005
        Upper bound T9630(normal) max_bytes_used: 40623419
        Actual      T9630(normal) max_bytes_used: 43490984
        Deviation   T9630(normal) max_bytes_used:     23.1 %
    *** unexpected stat test failure for T9630(normal)

This reverts commit 7271db46.
This reverts commit b750dcc5.
This reverts commit 33de71fa.

These were both improved by d92c7556 but the
changes were lost due to merge silliness.

Trac #15152 showed that when a flag turned an error into a warning, we
were still (alas) suppressing subequent errors; includign their
essential addTcEvBind.  That led (rightly) to a Lint error.

This patch fixes it, and incidentally tidies up an ad-hoc special
case of out-of-scope variables (see the old binding for
'out_of_scope_killer' in 'tryReporters').

No test, because the problem was only shown up when turning
inaccessible code into a warning.

Tobias Dammers authored 6 years ago and Ben Gamari committed 6 years ago

See #15019. When removing an unnecessary type equality check in #14737,
several regression tests failed. The cause was that some coercions that
are actually Refl coercions weren't passed in as such, which made the
equality check needlessly complex (Refl coercions can be discarded in
this particular check immediately, without inspecting the types at all).

We fix that, and get additional performance improvements for free.

Reviewers: goldfire, bgamari, simonpj

Reviewed By: bgamari, simonpj

Subscribers: simonpj, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4635

Alp Mestanogullari authored 6 years ago and Ben Gamari committed 6 years ago

A rather detailed summary can be found at:

    https://gist.github.com/alpmestan/be82b47bb88b7dc9ff84105af9b1bb82

This doesn't fix all expectation mismatches yet, but we're down to about
20 mismatches with my previous patch and this one, as opposed to ~150
when I got started.

Test Plan: ./validate --slow

Reviewers: bgamari, erikd, simonmar

Reviewed By: simonmar

Subscribers: thomie, carter

GHC Trac Issues: #14890

Differential Revision: https://phabricator.haskell.org/D4636

Trying to determine when to insert parentheses during TH
conversion is a bit of a mess. There is an assortment of functions
that try to detect this, such as:

* `hsExprNeedsParens`
* `isCompoundHsType`
* `hsPatNeedsParens`
* `isCompoundPat`
* etc.

To make things worse, each of them have slightly different semantics.
Plus, they don't work well in the presence of explicit type
signatures, as #14875 demonstrates.

All of these problems can be alleviated with the use of an explicit
precedence argument (much like what `showsPrec` currently does). To
accomplish this, I introduce a new `PprPrec` data type, and define
standard predences for things like function application, infix
operators, function arrows, and explicit type signatures (that last
one is new). I then added `PprPrec` arguments to the various
`-NeedsParens` functions, and use them to make smarter decisions
about when things need to be parenthesized.

A nice side effect is that functions like `isCompoundHsType` are
now completely unneeded, since they're simply aliases for
`hsTypeNeedsParens appPrec`. As a result, I did a bit of refactoring
to remove these sorts of functions. I also did a pass over various
utility functions in GHC for constructing AST forms and used more
appropriate precedences where convenient.

Along the way, I also ripped out the existing `TyPrec`
data type (which was tailor-made for pretty-printing `Type`s) and
replaced it with `PprPrec` for consistency.

Test Plan: make test TEST=T14875

Reviewers: alanz, goldfire, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14875

Differential Revision: https://phabricator.haskell.org/D4688

Chaitanya Koparkar authored 6 years ago and Ben Gamari committed 6 years ago

Test Plan: validate

Reviewers: bgamari, RyanGlScott, osa1

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #15055

Differential Revision: https://phabricator.haskell.org/D4669

Refactor LitString so that the string length is computed at most once
and then stored.

Also remove strlen and memcmp wrappers (it seems like they were a
workaround for a very old GCC when using -fvia-C).

Bumps haddock submodule.

Reviewers: bgamari, dfeuer, nickkuk

Reviewed By: bgamari, nickkuk

Subscribers: nickkuk, dfeuer, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4630

Ben Gamari authored 6 years ago and Ben Gamari committed 6 years ago

Summary: This fixes #15067.

Test Plan: Validate

Subscribers: thomie, carter, RyanGlScott

GHC Trac Issues: #15067

Differential Revision: https://phabricator.haskell.org/D4623

Matthew Pickering authored 6 years ago and Ben Gamari committed 6 years ago

This patch takes the much simpler route of whenever the compiler tries
to output something. We just dump a JSON document there and then.

I think this should be sufficient to work with and anything more refined
quickly got complicated as it was necessary to demarcate message scopes
and so on.

Reviewers: bgamari, dfeuer

Reviewed By: bgamari

Subscribers: Phyx, dfeuer, rwbarton, thomie, carter

GHC Trac Issues: #14078

Differential Revision: https://phabricator.haskell.org/D4532

Summary:
The parser's calculation of source spans for `EmptyCase`
expressions was a bit off, leading to some wonky-looking error
messages. Easily fixed with some uses of `comb3` and `sLL`.

Test Plan: make test TEST=T15139

Reviewers: bgamari, simonpj

Reviewed By: simonpj

Subscribers: simonpj, rwbarton, thomie, mpickering, carter

GHC Trac Issues: #15139

Differential Revision: https://phabricator.haskell.org/D4685

Azel authored 6 years ago and Tamar Christina committed 6 years ago

Summary:
Uses Win32's System.Win32.Console.CtrlHandler.withConsoleCtrlHandler to add
to Windows's version of the timeout executable a CTRL-C/CTRL-BREAK
handler which does the close IO port/kill job cleanup, just in case.

Signed-off-by: ARJANEN Loïc Jean David <arjanen.loic@gmail.com>

Reviewers: Phyx, bgamari

Reviewed By: Phyx

Subscribers: dfeuer, thomie, carter

GHC Trac Issues: #12721

Differential Revision: https://phabricator.haskell.org/D4631

This reverts commit 5fe6aaa3.

We introduce a new Id for unused pointer values in unboxed sums that is
not CAFFY. Because the Id is not CAFFY it doesn't make non-CAFFY
definitions CAFFY, fixing #15038.

To make sure anything referenced by the new id will be retained we get a
stable pointer to in on RTS startup.

Test Plan: Passes validate

Reviewers: simonmar, simonpj, hvr, bgamari, erikd

Reviewed By: simonmar

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #15038

Differential Revision: https://phabricator.haskell.org/D4680

Summary:
Space leaks in GHCi emerge from time to time and tend to come back again
after they get fixed. This is an attempt to limit regressions by

* adding a reliable detection for some classes of space leaks in GHCi
* turning on leak checking for all GHCi tests in the test suite, so that
  we'll notice if the leak appears again.

The idea for detecting space leaks is quite simple:

* find some data that we expect to be GC'd later, make a weak pointer to it
* when we expect the data to be dead, do a `performGC` and then check
  the status of the weak pointer.

It would be nice to apply this trick to lots of things in GHC,
e.g. ensuring that HsSyn is not retained after the desugarer, or
ensuring that CoreSyn from the previous simplifier pass is not retained.

Test Plan: validate

Reviewers: bgamari, simonpj, erikd, niteria

Subscribers: thomie, carter

GHC Trac Issues: #15111

Differential Revision: https://phabricator.haskell.org/D4658

Summary:
The element type of `List` maybe a type family instacen, rather than a trivial type.
For example in Trac #14547,

```
{-# LANGUAGE TypeFamilies, OverloadedLists #-}

class Foo f where
        type It f
        foo :: [It f] -> f

data List a = Empty | a :! List a deriving Show

instance Foo (List a) where
        type It (List a) = a
        foo [] = Empty
        foo (x : xs) = x :! foo xs
```

Here the element type of `[]` is `It (List a)`, we should also normalize
it as `a`.

Test Plan: make test TEST="T14547"

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: thomie, carter

GHC Trac Issues: #14547

Differential Revision: https://phabricator.haskell.org/D4624

This reverts commit 981bf471.

The element type of `List` maybe a type family instacen, rather than a
trivial type.
For example in Trac #14547,

```
{-# LANGUAGE TypeFamilies, OverloadedLists #-}

class Foo f where
        type It f
        foo :: [It f] -> f

data List a = Empty | a :! List a deriving Show

instance Foo (List a) where
        type It (List a) = a
        foo [] = Empty
        foo (x : xs) = x :! foo xs
```

Here the element type of `[]` is `It (List a)`, we should also normalize
it as `a`.

Test Plan: make test TEST="T14547"

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: thomie, carter

GHC Trac Issues: #14547

Differential Revision: https://phabricator.haskell.org/D4624