This implements the `EmptyDataDeriving` proposal put forth in
https://github.com/ghc-proposals/ghc-proposals/blob/dbf51608/proposals/0006-deriving-empty.rst.
This has two major changes:

* The introduction of an `EmptyDataDeriving` extension, which
  permits directly deriving `Eq`, `Ord`, `Read`, and `Show` instances
  for empty data types.
* An overhaul in the code that is emitted in derived instances for
  empty data types. To see an overview of the changes brought forth,
  refer to the changes to the 8.4.1 release notes.

Test Plan: ./validate

Reviewers: bgamari, dfeuer, austin, hvr, goldfire

Reviewed By: bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #7401, #10577, #13117

Differential Revision: https://phabricator.haskell.org/D4047

This commit

  commit 85aa1f42
  Date:   Sun Oct 29 20:48:19 2017 -0400
    Fix #14390 by making toIfaceTyCon aware of equality

was a bit over-complicated. This patch simplifies the (horribly
ad-hoc) treatement of IfaceEqualityTyCon, and documents it better.

No visible change in behaviour.

and in comments

Michal Terepeta authored 7 years ago and Ben Gamari committed 7 years ago

This is another step for fixing #13825 and is based on D38 by Simon
Marlow.

The change allows storing multiple constructor fields within the same
word. This currently applies only to `Float`s, e.g.,
```
data Foo = Foo {-# UNPACK #-} !Float {-# UNPACK #-} !Float
```
on 64-bit arch, will now store both fields within the same constructor
word. For `WordX/IntX` we'll need to introduce new primop types.

Main changes:

- We now use sizes in bytes when we compute the offsets for
  constructor fields in `StgCmmLayout` and introduce padding if
  necessary (word-sized fields are still word-aligned)

- `ByteCodeGen` had to be updated to correctly construct the data
  types. This required some new bytecode instructions to allow pushing
  things that are not full words onto the stack (and updating
  `Interpreter.c`). Note that we only use the packed stuff when
  constructing data types (i.e., for `PACK`), in all other cases the
  behavior should not change.

- `RtClosureInspect` was changed to handle the new layout when
  extracting subterms. This seems to be used by things like `:print`.
  I've also added a test for this.

- I deviated slightly from Simon's approach and use `PrimRep` instead
  of `ArgRep` for computing the size of fields.  This seemed more
  natural and in the future we'll probably want to introduce new
  primitive types (e.g., `Int8#`) and `PrimRep` seems like a better
  place to do that (where we already have `Int64Rep` for example).
  `ArgRep` on the other hand seems to be more focused on calling
  functions.

Signed-off-by: Michal Terepeta <michal.terepeta@gmail.com>

Test Plan: ./validate

Reviewers: bgamari, simonmar, austin, hvr, goldfire, erikd

Reviewed By: bgamari

Subscribers: maoe, rwbarton, thomie

GHC Trac Issues: #13825

Differential Revision: https://phabricator.haskell.org/D3809

GHC was panicking when pretty-printing a heterogeneous
equality type constructor (#14390) because the function which
produced the type constructor, `toIfaceTyCon`, wasn't attaching the
appropriate `IfaceTyConSort` for equality type constructors, which
is `IfaceEqualityTyCon`. This is fixed easily enough.

Test Plan: make test TEST=T14390

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #14390

Differential Revision: https://phabricator.haskell.org/D4132

Depends on D4090

Reviewers: austin, bgamari, erikd, simonmar, alexbiehl

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4091

Ben Gamari authored 7 years ago and Ben Gamari committed 7 years ago

Here we add a flag to instruct the native code generator to add
alignment checks in all info table dereferences. This is helpful in
catching pointer tagging issues.

Thanks to @jrtc27 for uncovering the tagging issues on Sparc which
inspired this flag.

Test Plan: Validate

Reviewers: simonmar, austin, erikd

Reviewed By: simonmar

Subscribers: rwbarton, trofi, thomie, jrtc27

Differential Revision: https://phabricator.haskell.org/D4101

Ben Gamari authored 7 years ago and Ben Gamari committed 7 years ago

Hopefully these are more robust to NFS malfunction than BSD flock-style
locks.  See #13945.

Test Plan: Validate via @simonpj

Reviewers: austin, hvr

Subscribers: rwbarton, thomie, erikd, simonpj

GHC Trac Issues: #13945

Differential Revision: https://phabricator.haskell.org/D4129

The idea is described in #14152, and can be summarized: Float the exit
path out of a joinrec, so that the simplifier can do more with it.
See the test case for a nice example.

The floating goes against what the simplifier usually does, hence we
need to be careful not inline them back.

The position of exitification in the pipeline was chosen after a small
amount of experimentation, but may need to be improved. For example,
exitification can allow rewrite rules to fire, but for that it would
have to happen before the `simpl_phases`.

Perf.haskell.org reports these nice performance wins:

    Nofib allocations
    fannkuch-redux    78446640  - 99.92%      64560
    k-nucleotide     109466384  - 91.32%    9502040
    simple            72424696  -  5.96%   68109560

    Nofib instruction counts
    fannkuch-redux  1744331636  -  3.86% 1676999519
    k-nucleotide    2318221965  -  6.30% 2172067260
    scs             1978470869  -  3.35% 1912263779
    simple           669858104  -  3.38%  647206739
    spectral-norm    186423292  -  5.37%  176411536

Differential Revision: https://phabricator.haskell.org/D3903

Previously, (since 33452dfc), simplNonRecJoinPoint would do the wrong
thing in the presence of shadowing: It analyzed the RHS of a join
binding with the environment for the body. In particular, with

    foo x =
      join x = x * x
      in x

where there is shadowing, it renames the inner x to x1, and should
produce

    foo x =
      join x1 = x * x
      in x1

but because the substitution (x ↦ x1) is also used on the RHS we get the
bogus

    foo x =
      join x1 = x1 * x1
      in x1

Fixed this by adding a `rhs_se` parameter, analogous to `simplNonRecE`
and `simplLazyBind`.

Differential Revision: https://phabricator.haskell.org/D4130

Computing the number of constructors for TyCon is linear
in the number of constructors.
That's wasteful if all you want to check is if that
number is smaller than what fits in tag bits
(usually 8 things).

What this change does is to use a function that can
determine the ineqaulity without computing the size.

This improves compile time on a module with a
data type that has 10k constructors.
The variance in total time is (suspiciously) high,
but going by the best of 3 the numbers are 8.186s vs 7.511s.
For 1000 constructors the difference isn't noticeable:
0.646s vs 0.624s.
The hot spots were cgDataCon and cgEnumerationTyCon
where tagForCon is called in a loop.

One alternative would be to pass down the size.

Test Plan: harbormaster

Reviewers: bgamari, simonmar, austin

Reviewed By: simonmar

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4116

Summary:
It's simple to treat BodyStmt just like a BindStmt with a wildcard
pattern, which is enough to fix #12143 without going all the way to
using `<*` and `*>` (#10892).

Test Plan:
* new test cases in `ado004.hs`
* validate

Reviewers: niteria, simonpj, bgamari, austin, erikd

Subscribers: rwbarton, thomie

GHC Trac Issues: #12143

Differential Revision: https://phabricator.haskell.org/D4128

Trac #14379 showed a case where use of "forcing" to do
"damn the torpedos" specialisation without resource limits
(which 'vector' does a lot) led to exponential blowup.

The fix is easy.  Finding it wasn't.  See Note [Forcing
specialisation] and the one-line change in decreaseSpecCount.

Do not use $SHELL as $SHELL is the user's preferred interactive shell.
We do not want this to leak into the wrapper scripts.

This is breaking the build on some platforms. It's unclear exactly why but I
don't have time to investigate at the moment.

[skip ci]

Tobias Dammers authored 7 years ago and Ben Gamari committed 7 years ago

Improves compiler performance of deriving Read instances, as suggested
in the issue.

Additionally, we introduce `readSymField`, a companion to `readField`
that parses symbol-type fields (where the field name is a symbol, e.g.
`(#)`, rather than an alphanumeric identifier. The decision between
these two functions is made a compile time, because we already know
which one we need based on the field name.

Reviewers: austin, hvr, bgamari, RyanGlScott

Reviewed By: bgamari

Subscribers: RyanGlScott, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4108

Douglas Wilson authored 7 years ago and Ben Gamari committed 7 years ago

Test Plan: Consider whether this is a good idea.

Reviewers: austin, hvr, bgamari, nomeata

Reviewed By: bgamari, nomeata

Subscribers: nomeata, rwbarton, thomie

GHC Trac Issues: #14387

Differential Revision: https://phabricator.haskell.org/D4126

Ben Gamari authored 7 years ago and Ben Gamari committed 7 years ago

Begins to fix #14214.

[skip ci]

Test Plan: Read it.

Reviewers: austin

Subscribers: rwbarton, thomie

GHC Trac Issues: #14214

Differential Revision: https://phabricator.haskell.org/D4098

Alec Theriault authored 7 years ago and Ben Gamari committed 7 years ago

The lexer hacks around unicode by squishing any character into a 'Word8'
and then storing the actual character in its state. This happens at
'alexGetByte'.

That is all and well, but we ought to be careful that the characters we
retrieve via 'alexInputPrevChar' also fit this convention.

In fact, #13986 exposes nicely what can go wrong: the regex in the left
context of the type application rule uses the '$idchar' character set
which relies on the unicode hack. However, a left context corresponds
to a call to 'alexInputPrevChar', and we end up passing full blown
unicode characters to '$idchar', despite it not being equipped to deal
with these.

Test Plan: Added a regression test case

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #13986

Differential Revision: https://phabricator.haskell.org/D4105

Daishi Nakajima authored 7 years ago and Ben Gamari committed 7 years ago

Warning on declaring a partial record selector.
However, disable warn with field names that start with underscore.

Test Plan: Added 1 test case.

Reviewers: austin, bgamari, simonpj

Reviewed By: bgamari, simonpj

Subscribers: goldfire, simonpj, duog, rwbarton, thomie

GHC Trac Issues: #7169

Differential Revision: https://phabricator.haskell.org/D4083

Tobias Dammers authored 7 years ago and Ben Gamari committed 7 years ago

When allocating and potentially spilling registers, we need to check
the desired allocations against current allocations to decide where we
can spill to, cq. which allocations we can toss and if so, how.
Previously, this was done by walking the Cartesian product of the
current allocations (`assig`) and the allocations to keep (`keep`),
which has quadratic complexity. This patch introduces two improvements:

1. pre-filter the `assig` list, because we are only interested in two
types of allocations (in register, and in register+memory), which will
only make up a small and constant portion of the list; and
2. use set / map operations instead of lists, which reduces algorithmic
complexity.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4109

Douglas Wilson authored 7 years ago and Ben Gamari committed 7 years ago

Replace a call to mapAccumR, which uses linear stack space, with a
gadget that uses constant space.

Remove an unused parameter from fromOnDiskName.

The tests T1292_imports and T4239 are now reporting imported names in a
different order. I don't completely understand why, but I presume it is
because the symbol tables are now read more strictly. The new order
seems better in T1792_imports, and equally random in T4239.

There are several performance test improvements.

Test Plan: ./validate

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: alexbiehl, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4124

Tamar Christina authored 7 years ago and Ben Gamari committed 7 years ago

This fixes the mirror script so it correctly queries haskell.org and if
packages aren't found check repo.msys2.org.

Also the mirror functionality now generates the md5 hashes after a
mirror fetch that can be placed in the md5sums file.

Test Plan:
 mk/get-win32-tarballs.sh fetch mirror

 and ./validate

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4118

Tobias Dammers authored 7 years ago and Ben Gamari committed 7 years ago

Making the pretty-printer based assembly output stricter in
strategically chosen locations produces a minor performance improvement
when compiling large derived Read instance (on the order of 5-10%).

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4111

I.e. instead of

    .. ghc-flag:: -XUnboxedTuples
        :shortdesc: Enable the use of unboxed tuple syntax.
        :type: dynamic
        :reverse: -XNoUnboxedTuples
        :category:

one simply writes

    .. extension:: UnboxedTuples
        :shortdesc: Enable the use of unboxed tuple syntax.

This allows language extensions to be referenced as

    If :extension:`UnboxedTuples` is enabled, then...

This directive still creates the entries for the `-XUnboxedTuples` flag,
so in particular,

    Set :ghc-flag:`-XUnboxedTuples` if you have to.

still works, and lists of flags in general (e.g. for the manpage)
include these.

I also removed lots of links from the shortdesc of the extensions, when
this link simply points to the section where the extension is defined.

I removed the list of `-X` flags from the flag reference table, but added a
table of extension under “10.1. Language options”

Lots of text in the manual now refers to “extension `Foo`” rather than
“flag `-XFoo`”.

I consider `-XFoo` a historic artifact that stems from when language
extensions were really just flags. These days, the use of `-XFoo` is
(IMHO) deprecated: You should be using `LANGUAGE Foo`, or maybe the
appropriate field in a `.cabal` file. See 9278994a which did this change
to error messages already.

Differential Revision: https://phabricator.haskell.org/D4112

This reverts commit 561bdca1.

submodule