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This major commit was initially triggered by #11339, but it spiraled
into a major review of the way in which type signatures for bindings
are handled, especially partial type signatures.  On the way I fixed a
number of other bugs, namely
   #12069
   #12033
   #11700
   #11339
   #11670

The main change is that I completely reorganised the way in which type
signatures in bindings are handled. The new story is in TcSigs
Note [Overview of type signatures].  Some specific:

* Changes in the data types for signatures in TcRnTypes:
  TcIdSigInfo and new TcIdSigInst

* New module TcSigs deals with typechecking type signatures
  and pragmas. It contains code mostly moved from TcBinds,
  which is already too big

* HsTypes: I swapped the nesting of HsWildCardBndrs
  and HsImplicitBndsrs, so that the wildcards are on the
  oustide not the insidde in a LHsSigWcType.  This is just
  a matter of convenient, nothing deep.

There are a host of other changes as knock-on effects, and
it all took FAR longer than I anticipated :-).  But it is
a significant improvement, I think.

Lots of error messages changed slightly, some just variants but
some modest improvements.

New tests

* typecheck/should_compile
    * SigTyVars: a scoped-tyvar test
    * ExPat, ExPatFail: existential pattern bindings
    * T12069
    * T11700
    * T11339

* partial-sigs/should_compile
    * T12033
    * T11339a
    * T11670

One thing to check:

* Small change to output from ghc-api/landmines.
  Need to check with Alan Zimmerman

This patch simply deletes code, the SigTv check in
occurCheckExpand.  As the new comment says

In the past we also rejected a SigTv matched with a non-tyvar
But it is wrong to reject that for Givens;
and SigTv is in any case handled separately by
   - TcUnify.checkTauTvUpdate (on-the-fly unifier)
   - TcInteract.canSolveByUnification (main constraint solver)

The NUMA code was enabled whenever numa.h and numaif.h are detected.
Unfortunately, the hosts' header files were being detected even then
cross compiling in the absence of a target libnuma.

Fix that by relying on the the presence of libnuma instead of the
presence of the header files. The test for libnuma does `AC_TRY_LINK`
which will fail if the test program (compiled for the target) can't
be linked against libnuma.

Test Plan:
Build on x86_64/linux and make sure NUMA works and cross compile to
armhf/linux.

Reviewers: austin, bgamari, hvr, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2329

Summary:
See #12031 for analysis, but essentially what happens is:

To sum up the issue, the reason this seems to go wrong is because
of how we initialize the `.bss` section for Windows in the runtime linker.

The first issue is where we calculate the zero space for the section:

```
zspace = stgCallocBytes(1, bss_sz, "ocGetNames_PEi386(anonymous bss)");
sectab_i->PointerToRawData = ((UChar*)zspace) - ((UChar*)(oc->image));
```

Where
```
UInt32 PointerToRawData;
```

This means we're stuffing a `64-bit` value into a `32-bit` one. Also `zspace`
can be larger than `oc->image`. In which case it'll overflow and
then get truncated in the cast.

The address of a value in the `.bss` section is then calculated as:

```
addr = ((UChar*)(oc->image))
     + (sectabent->PointerToRawData
     + symtab_i->Value);
```

If it does truncate then this calculation won't be correct (which is what is happening).

We then later use the value of `addr` as the `S` (Symbol) value for the relocations

```
S = (size_t) lookupSymbol_( (char*)symbol );
```

Now the majority of the relocations are `R_X86_64_PC32` etc.
e.g. They are guaranteed to fit in a `32-bit` value.

The `R_X86_64_64` introduced for these pseudo-relocations so they can use
the full `48-bit` addressing space isn't as lucky.
As for why it sometimes work has to do on whether the value is truncated or not.

`PointerToRawData` can't be changed because it's size is fixed by the PE specification.

Instead just like with the other platforms, we now use `section` on Windows as well.
This gives us a `start` parameter of type `void*` which solves the issue.

This refactors the code to use `section.start` and to fix the issues.

Test Plan: ./validate and new test added T12031

Reviewers: RyanGlScott, erikd, bgamari, austin, simonmar

Reviewed By: simonmar

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2316

GHC Trac Issues: #12031, #11317

See #11204, this test sometimes fails and sometimes passes on OSX
which causes intermittent validate failures if it is run.

The recently added NUMA related functions were mistakenly defined
within a `#ifdef USE_LARGE_ADDRESS_SPACE` ... `#endif` block. Moving
them outside this block fixes the build on PowerPC and Arm Linux.

Test Plan: Build on PowerPC or Arm Linux

Reviewers: hvr, austin, bgamari, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2326

* Remove unused/old flags from the structs
* Update old comments
* Add missing flags to GHC.RTS
* Simplify GHC.RTS, remove C code and use hsc2hs instead
* Make ParFlags unconditional, and add support to GHC.RTS

Summary:
The aim here is to reduce the number of remote memory accesses on
systems with a NUMA memory architecture, typically multi-socket servers.

Linux provides a NUMA API for doing two things:
* Allocating memory local to a particular node
* Binding a thread to a particular node

When given the +RTS --numa flag, the runtime will
* Determine the number of NUMA nodes (N) by querying the OS
* Assign capabilities to nodes, so cap C is on node C%N
* Bind worker threads on a capability to the correct node
* Keep a separate free lists in the block layer for each node
* Allocate the nursery for a capability from node-local memory
* Allocate blocks in the GC from node-local memory

For example, using nofib/parallel/queens on a 24-core 2-socket machine:

```
$ ./Main 15 +RTS -N24 -s -A64m
  Total   time  173.960s  (  7.467s elapsed)

$ ./Main 15 +RTS -N24 -s -A64m --numa
  Total   time  150.836s  (  6.423s elapsed)
```

The biggest win here is expected to be allocating from node-local
memory, so that means programs using a large -A value (as here).

According to perf, on this program the number of remote memory accesses
were reduced by more than 50% by using `--numa`.

Test Plan:
* validate
* There's a new flag --debug-numa=<n> that pretends to do NUMA without
  actually making the OS calls, which is useful for testing the code
  on non-NUMA systems.
* TODO: I need to add some unit tests

Reviewers: erikd, austin, rwbarton, ezyang, bgamari, hvr, niteria

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2199

Use tauifyExpType rather than something hand-rolled

...about unarisation and unboxed tuples

Remove -fwarn- and -fno-warn- from flagsForCompletion

Testcase: Fix linter error on T12099

For Issue #12099

Reviewers: austin, thomie, bgamari

Reviewed By: austin, thomie, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2281

GHC Trac Issues: #12099

It turns out this function was unused and broken for a long time (fixed
with b0a76643). Removing it as it will probably get broken again in the
future and it's unused.

Reviewers: austin, erikd, simonmar, nomeata, bgamari

Reviewed By: nomeata, bgamari

Subscribers: Phyx, thomie, nomeata

Differential Revision: https://phabricator.haskell.org/D2322

(This fixes segfaults)

Now the message explains why closed variables are not closed when
encountered in the body of (static ...).

This required adding to the local environment the free variables of
the local bindings in scope. Thus we can analyze and explain why a
variable is not closed when encountered.

Test Plan: ./validate

Reviewers: austin, simonpj, bgamari

Reviewed By: bgamari

Subscribers: mboes, thomie

Differential Revision: https://phabricator.haskell.org/D2167

GHC Trac Issues: #12003

Summary:
The histogram types are defined in `Ticky.c` as `StgInt` values.

```
EXTERN StgInt RET_NEW_hst[TICKY_BIN_COUNT] INIT({0});
EXTERN StgInt RET_OLD_hst[TICKY_BIN_COUNT] INIT({0});
EXTERN StgInt RET_UNBOXED_TUP_hst[TICKY_BIN_COUNT] INIT({0});
```

which means they'll be `32-bits` on `x86` and `64-bits` on `x86_64`.

However the `bumpHistogram` in `StgCmmTicky` is incrementing them as if
they're a `cLong`. A long on Windows `x86_64` is `32-bit`.

As such when then value for the `_hst_1` is being set what it's actually doing
is setting the value of the high bits of the first entry.

This ends up giving us `0b‭100000000000000000000000000000000‬` or `4294967296`
as is displayed in the ticket on #8308.

Since `StgInt` is defined using the `WORD` size. Just use that directly in
`bumpHistogram`.

Also since `cLong` is no longer used after this commit it will also be dropped.

Test Plan: make TEST=T8308

Reviewers: mlen, jstolarek, bgamari, thomie, goldfire, simonmar, austin

Reviewed By: bgamari, thomie

Subscribers: #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2318

GHC Trac Issues: #8308

Since `-XPatternGuards` is enabled by default, invert the logic and
mention `-XNoPatternGuards` first.

Also, since this is a Haskell 2010 feature, refer to the language report
instead of explaining it.

In general, I would like to follow the guideline of assuming the latest
language report as a given, and then only report GHC's deviations and
extensions relative to that report.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D2319

GHC Trac Issues: #12172

It uses Ord DataCon which uses Ord Unique which is
nondeterministic

GHC Trac: #4012

It's implemented in terms of Unique which is nondeterministic

GHC Trac: #4012

It was implemented in terms of Unique which is nondeterministic

GHC Trac: #4012

It was implemented in terms of Uniques, but fortunately it's unused
so we can remove it.

GHC Trac: #4012

Eq TyCon is defined in terms of Ord TyCon, but we want to
remove Ord TyCon, because it's implemented in terms of unique
comparison, which is nondeterministic.

GHC Trac: #4012

Summary:
Remove some Windows specific code from the .m4 files
and have configure figure it out.

Unfortunately touchy can't be removed since there
is no mingw build of coreutils. Only msys builds
which would give us a dependency on the msys runtime.

Reviewers: hvr, austin, thomie, bgamari

Reviewed By: thomie, bgamari

Subscribers: thomie, erikd, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2248

Summary:
This mostly follows the plan detailed by the discussion
Simon and I had, with one difference: instead of grabbing
the free variables of the trivial expressions to get the
embedded Ids, we just use getIdFromTrivialExpr_maybe to extract
out the Id.  If there is no Id, the expression cannot
refer to a function (as there are no literal functions)
and thus we do not need to saturate.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2309

GHC Trac Issues: #12076

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Summary:
Comes with a test based off of prog006.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2221

GHC Trac Issues: #12064

This fixes the problem with duplicate cost-centre names that was
reported a couple of times before. When a module implements a typeclass
multiple times for different types, methods of different implementations
get same cost-centre names and are reported like this:

    COST CENTRE MODULE            %time %alloc

    CAF         GHC.IO.Handle.FD    0.0   32.8
    CAF         GHC.Read            0.0    1.0
    CAF         GHC.IO.Encoding     0.0    1.8
    showsPrec   Main                0.0    1.2
    readPrec    Main                0.0   19.4
    readPrec    Main                0.0   20.5
    main        Main                0.0   20.2

                                            individual      inherited
    COST CENTRE  MODULE  no.     entries  %time %alloc   %time %alloc

    MAIN         MAIN     53          0    0.0    0.2     0.0  100.0
     CAF         Main    105          0    0.0    0.3     0.0   62.5
      readPrec   Main    109          1    0.0    0.6     0.0    0.6
      readPrec   Main    107          1    0.0    0.6     0.0    0.6
      main       Main    106          1    0.0   20.2     0.0   61.0
       ==        Main    114          1    0.0    0.0     0.0    0.0
       ==        Main    113          1    0.0    0.0     0.0    0.0
       showsPrec Main    112          2    0.0    1.2     0.0    1.2
       showsPrec Main    111          2    0.0    0.9     0.0    0.9
       readPrec  Main    110          0    0.0   18.8     0.0   18.8
       readPrec  Main    108          0    0.0   19.9     0.0   19.9

It's not possible to tell from the report which `==` took how long. This
patch adds one more column at the cost of making outputs wider. The
report now looks like this:

    COST CENTRE MODULE           SRC                       %time %alloc

    CAF         GHC.IO.Handle.FD <entire-module>             0.0   32.9
    CAF         GHC.IO.Encoding  <entire-module>             0.0    1.8
    CAF         GHC.Read         <entire-module>             0.0    1.0
    showsPrec   Main             Main_1.hs:7:19-22           0.0    1.2
    readPrec    Main             Main_1.hs:7:13-16           0.0   19.5
    readPrec    Main             Main_1.hs:4:13-16           0.0   20.5
    main        Main             Main_1.hs:(10,1)-(20,20)    0.0   20.2

                                                                       individual      inherited
    COST CENTRE  MODULE        SRC                      no. entries  %time %alloc   %time %alloc

    MAIN         MAIN          <built-in>                53      0    0.0    0.2     0.0  100.0
     CAF         Main          <entire-module>          105      0    0.0    0.3     0.0   62.5
      readPrec   Main          Main_1.hs:7:13-16        109      1    0.0    0.6     0.0    0.6
      readPrec   Main          Main_1.hs:4:13-16        107      1    0.0    0.6     0.0    0.6
      main       Main          Main_1.hs:(10,1)-(20,20) 106      1    0.0   20.2     0.0   61.0
       ==        Main          Main_1.hs:7:25-26        114      1    0.0    0.0     0.0    0.0
       ==        Main          Main_1.hs:4:25-26        113      1    0.0    0.0     0.0    0.0
       showsPrec Main          Main_1.hs:7:19-22        112      2    0.0    1.2     0.0    1.2
       showsPrec Main          Main_1.hs:4:19-22        111      2    0.0    0.9     0.0    0.9
       readPrec  Main          Main_1.hs:7:13-16        110      0    0.0   18.8     0.0   18.8
       readPrec  Main          Main_1.hs:4:13-16        108      0    0.0   19.9     0.0   19.9
     CAF         Text.Read.Lex <entire-module>          102      0    0.0    0.5     0.0    0.5

To fix failing test cases because of different orderings of cost centres
(e.g. optimized and non-optimized build printing in different order),
with this patch we also start sorting cost centres before printing. The
order depends on 1) entries (more entered cost centres come first) 2)
names (using strcmp() on cost centre names).

Reviewers: simonmar, austin, erikd, bgamari

Reviewed By: simonmar, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2282

GHC Trac Issues: #11543, #8473, #7105

This is the proper fix for the problem I tried solve with D2310
(committed as dd332459 and reverted in 44a3c182).

Reviewers: austin, goldfire, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2315

This reverts commit dd332459.

It seems like we already have `endPassIO` calls here, which should print
term sizes. For some reason they don't sometimes, and we need to
understand why instead of adding more prints.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2310

These are the tests that I accumulated fixing real issues.
Each test is a separate thing that was broken and they are
relatively small.

GHC Trac: #4012

This makes sure the testsuite keeps working when testdir contains
backward slashes.

Differential Revision: https://phabricator.haskell.org/D2314