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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)

(cherry picked from commit d25cb61a)

There was an awful leak where GHC permitted standalone `deriving`
declarations to create instances for unboxed sum or tuple types. This
fortifies the checks that GHC performs to catch this scenario and give
an appropriate error message.

Fixes #11509.

Test Plan: ./validate

Reviewers: goldfire, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2557

GHC Trac Issues: #11509

(cherry picked from commit 23cf32da)

This fixes Trac #12597: in RnNames.warnMissingSignatures,
use pprSigmaType not pprType

(cherry picked from commit 796f0f2a)

With this patch we stop generating virtual semicolons in MultiWayIf
guards. Fixes #10807.

Test Plan:

Reviewers: simonmar, austin, bgamari

Reviewed By: simonmar

Subscribers: mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2524

GHC Trac Issues: #10807

(cherry picked from commit c36904d6)

This patch fixes Trac #12595.  The problem was with a
pattern binding like
     !x = e
For a start it's silly to match that pattern and build
a unit tuple (the General Case of mkSelectorBinds); but
that's what was happening because the bang fell through
to the general case.  But for a variable pattern building
any auxiliary bindings is stupid.  So the patch
introduces a new case in mkSelectorBinds for variable
patterns.

Then it turned out that if 'e' was a plain variable, and
moreover was imported GlobalId, then matchSinglePat made
it a /bound/ variable, which should never happen.  That
ultimately caused a linker error, but the original bug
was much earlier.

(cherry picked from commit 2fbfbca2)

We were missing an appropiate *ConLike lookup in the case when
the pattern synonym was defined in a different module.

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D2544

GHC Trac Issues: #11987

(cherry picked from commit 2d6642bd)

When DuplicateRecordFields is enabled, the mangling of selector names
was causing them to be reported as unused even if prefixed by an
underscore. This corrects the OccName used by the check.

Test Plan: New test overloadedrecflds/should_compile/T12609

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2549

GHC Trac Issues: #12609

(cherry picked from commit 48ff0843)

Previously the renamer assumed that *any* time we renamed a pattern, the
pattern was introducing new binders. This isn't true in pattern synonym
declarations where the pattern is used as part of a definition.

We add a special case to not warn in this situation.

Reviewers: simonpj, austin, bgamari

Reviewed By: simonpj

Subscribers: simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D2545

GHC Trac Issues: #12615

(cherry picked from commit 1851349a)

Opcode lwa is a 64-bit opcode and allows a DS-form only.  This patch
generates lwa opcodes only when the offset is a multiple of 4.

Fixes #12621

Test Plan: validate

Reviewers: erikd, hvr, simonmar, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2547

GHC Trac Issues: #12621

(cherry picked from commit ce3370e0)

Foreign calls (unsafe and safe) interact badly with inlining and
register passing ABIs (see #11792 and #12614):
the inlined code to compute a parameter of the call may overwrite a
register already set to pass a preceding parameter.

With this patch, we compute all parameters which are not simple
expressions before assigning them to fixed registers required by the
ABI.

Test Plan:
   - Add test (test both reg and stack parameters)
   - Validate

Reviewers: osa1, bgamari, austin, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2263

GHC Trac Issues: #11792, #12614

(cherry picked from commit b61b7c24)

Fixes #12519.

The following command fails as:
    $ ./configure --prefix=/usr \
        --build=x86_64-pc-linux-gnu \
        --host=x86_64-pc-linux-gnu \
        --target=x86_64-pc-linux-gnu
    configure: error:
    You've selected:

      BUILD:  x86_64-unknown-linux
      HOST:   x86_64-unknown-linux
      TARGET: x86_64-unknown-linux

    BUILD must equal HOST;

18f06878 changed native
configure $build/$host/$target checks to ghc-mangled ones,
but not completely.
Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Reviewers: rwbarton, erikd, austin, hvr, bgamari, Phyx

Reviewed By: Phyx

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2508

GHC Trac Issues: #12487

(cherry picked from commit 0cc3931b)

Summary:
GHC's configure script seems to normalize the values returned from config.guess.
So for Windows it turns x86_64-pc-mingw64 into x86_64-unknown-mingw32.
These mangled names are stored in the values $BuildPlatform, $HostPlatform
and $TargetPlatform.

However further down the file when the comparison is done between the stage0
compiler and the host the normalized versions are not used.
So when normalization actually changes the triple this check will fail.

Not sure why it's worked for all this time.. Nor if this is the right fix?
Does it still work for cross compiling correctly?

Test Plan: ./configure

Reviewers: hvr, austin, thomie, bgamari, erikd

Reviewed By: erikd

Subscribers: erikd, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2452

GHC Trac Issues: #12487

(cherry picked from commit 18f06878)

... that we grep out of libraries/Cabal/Cabal/Cabal.cabal

This is necessary because the file got reformatted
in the 'master' branch.

(cherry picked from commit 1101045c)

This fixes Trac #12531:

   class Foo x where
     foo :: forall a . x a -> x a
     default foo :: forall b . x b -> x b
     foo x = go
       where go :: x b
             go = undefined

We want 'b' to scope over the code for 'foo', but we were
using 'a' instead.

(cherry picked from commit 0050aff2)

This snuck into c51caafa.

The old testsuite driver still requires a relative path to Defer02.

I must have failed to validate properly, sorry.
These testsuite wibbles belong with

  commit 03541cba
  Author: Simon Peyton Jones <simonpj@microsoft.com>
  Date:   Fri Sep 9 17:42:42 2016 +0100

      Be less picky about reporing inaccessible code

(cherry picked from commit 5eeabe25)

Triggered by the discussion on Trac #12466, this patch
makes GHC less aggressive about reporting an error when
there are insoluble Givens.

Being so agressive was making some libraries fail to
compile, and is arguably wrong in at least some cases.
See the discussion on the ticket.

Several test now pass when they failed before; see
the files-modified list for this patch.

(cherry picked from commit 03541cba)

...thereby being able to replace substThetaUnchecked
with substTheta

(cherry picked from commit 7afb7adf)

This had an extra_files directive, which does not exist in ghc-8.0, from
cherry-picking.

In an instance declaration when you don't specify the code for a
method, GHC fills in from the default binding in the class.
The type of the default method can legitmiately be ambiguous ---
see Note [Default methods in instances] in TcInstDcls --- so
typechecking it can be tricky.

Trac #12220 showed that although we were dealing with that ambiguity
for /vanilla/ default methods, we were not doing so for /generic/
default methods.  Moreover we were dealing with it clumsily, by
generating post-typechecked code.

This patch fixes the bug AND deletes code!  We now use the same code
path for both vanilla and generic default methods; and generate
/pre-typechecked/ code in both cases.  The key trick is that we can use
Visible Type Application to deal with the ambiguity, which wasn't
possible before.  Hooray.

There is a small hit to performance in compiler/perf/T1969 which
consists of nothing BUT instance declarations with several default
methods to fill, which we now have to typecheck. The actual hit is
from 724 -> 756 or 4% in that extreme example.  Real world programs
have vastly fewer instance decls.

(cherry picked from commit d2958bd0)

Summary:
* getNonClobberedReg instead of getSomeReg, because the reg needs to
  survive across t_code
* Use a new reg for the table offset calculation instead of clobbering
  the reg returned by expr (this was the bug affecting #12433)

Test Plan: New unit test; validate

Reviewers: rwbarton, bgamari, austin, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2529

GHC Trac Issues: #12433

Test Plan: Validate

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2517

GHC Trac Issues: #11433

(cherry picked from commit dcc49044)

Biographical profiling is not thread-safe as documented in #12019. Throw
an error when it is used in this way.

Test Plan: Validate

Reviewers: simonmar, austin, erikd

Reviewed By: erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2516

GHC Trac Issues: #12019

(cherry picked from commit 6555c6bb)

Summary:
We stumbled upon a case where an external library (OpenCL) does not work
if a specific address (0x200000000) is taken.

It so happens that `osReserveHeapMemory` starts trying to mmap at 0x200000000:

```
        void *hint = (void*)((W_)8 * (1 << 30) + attempt * BLOCK_SIZE);
        at = osTryReserveHeapMemory(*len, hint);
```

This makes it impossible to use Haskell programs compiled with GHC 8
with C functions that use OpenCL.

See this example ​https://github.com/chpatrick/oclwtf for a repro.

This patch allows the user to work around this kind of behavior outside
our control by letting the user override the starting address through an
RTS command line flag.

Reviewers: bgamari, Phyx, simonmar, erikd, austin

Reviewed By: Phyx, simonmar

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D2513

(cherry picked from commit 1b5f9207)

A folow-up to D2521 (which addressed #12583), where the `Outputable` `ppr`
output was tweaked to display a list comprehension with only one `Stmt` as
`[Foo]` instead of `[Foo|]` (which isn't valid Haskell). I forgot to update
the corresponding code in `Language.Haskell.TH.Ppr` which pretty-prints
`CompE`, however, so this commit takes care of that.

(cherry picked from commit 0e7ccf6d)

Standalone-derived `Ix` instances would panic on GADTs with exactly
one constructor, since the list of fields was being passed to a function that
uses `foldl1` in order to generate an implementation for `inRange`. This adds a
simple check that makes `inRange` be `True` whenever a product type has no
fields.

Fixes #12583.

Test Plan: make test TEST=12583

Reviewers: simonpj, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2521

GHC Trac Issues: #12583

(cherry picked from commit 7b7ea8f4)

Fixes readdir validation error (fixes #12572).
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
(cherry picked from commit a8238a4e)

Summary:
The generated documentation for thhe Foreign.C.Types
module is generated based on the platform which ran Haddock.

This is generating incorrect types for e.g. Windows.

Add a disclaimer to the top of the page to ask people to
keep this in mind.

Test Plan: make documentation and inspect Haddock

Reviewers: erikd, austin, hvr, bgamari

Reviewed By: erikd

Subscribers: RyanGlScott, #ghc_windows_task_force, thomie

Differential Revision: https://phabricator.haskell.org/D2523

GHC Trac Issues: #12586

(cherry picked from commit 710f21cc)

Summary:
The external interpreter is launched by calling
'System.Process.createProcess' with a 'CreateProcess' parameter.

The current value for this has the 'std_in', 'std_out' and 'std_err'
fields use the default of 'Inherit', meaning that the remote interpreter
shares the stdio with the original ghc/ghci process.

This patch introduces a new hook to the DynFlags, which has an
opportunity to override the 'CreateProcess' fields, launch the process,
and retrieve the stdio handles actually used.

So if a ghci external interpreter session is launched from the GHC API
the stdio can be redirected if required, which is useful for tooling/IDE
integration.

Test Plan: ./validate

Reviewers: austin, hvr, simonmar, bgamari

Reviewed By: simonmar, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2518

(cherry picked from commit 65d9597d)

Test Plan: none

Reviewers: austin, niteria, bgamari

Reviewed By: niteria

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2514

GHC Trac Issues: #12485

(cherry picked from commit 5eab6a0d)

Reviewers: austin, bgamari, ezyang

Reviewed By: ezyang

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2464

(cherry picked from commit 6781f37d)

Test Plan: Read it

Reviewers: dfeuer, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2515

GHC Trac Issues: #11691

(cherry picked from commit feaa31fb)

With BuildFlavour set to `perf-llvm`, GHCi would fail as soon as it
was run with:

  ghc-stage2: .../ghc-prim/dist-install/build/HSghc-prim-0.5.0.0.o:
  unknown symbol `__udivti3'
  ghc-stage2: unable to load package `ghc-prim-0.5.0.0'

Fix this by adding `__udivti3` and `__umodti3` to RtsSymbols.c.

Test Plan: Validate

Reviewers: simonmar, austin, bgamari, Phyx, trofi

Reviewed By: Phyx, trofi

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2449

GHC Trac Issues: #11981

(cherry picked from commit bd0c3106)

Previously instIsVisible had completely broken the laziness of
lookupInstEnv' since it would examine is_dfun_name to check the name of
the defining module (to know whether it is an interactive module). This
resulted in the visibility check drawing in an interface file
unnecessarily. This contributed to the unnecessary regression in
compiler allocations reported in #12367.

Test Plan: Validate, check nofib changes

Reviewers: simonpj, ezyang, austin

Reviewed By: ezyang

Subscribers: thomie, ezyang

Differential Revision: https://phabricator.haskell.org/D2411

GHC Trac Issues: #12367

(cherry picked from commit ed480981)

This fixes #11990.

The current rule is simpler than before: if we encounter an unsolved
constraint that contains any mentions of properly applied `TypeError`,
then we report the type error.

If there are multiple `TypeErrors`, then we just report one of them.

Reviewers: simonpj, bgamari, austin

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2151

GHC Trac Issues: #11990

(cherry picked from commit b75d1940)

As reported in #12555 this code was terribly broken. Sadly, Autoconf was
none-the-wiser. Thanks to @rwbarton for pointing this out.

Test Plan: Test with libdw version newer and older and 0.158

Reviewers: hvr, austin, rwbarton

Reviewed By: rwbarton

Subscribers: thomie, rwbarton, erikd

Differential Revision: https://phabricator.haskell.org/D2510

GHC Trac Issues: #12555

(cherry picked from commit 05b497ec)

Test Plan: Corrected a few tests to include the new message.

Reviewers: goldfire, austin, bgamari

Reviewed By: bgamari

Subscribers: goldfire, thomie

Differential Revision: https://phabricator.haskell.org/D2484

GHC Trac Issues: #12546

(cherry picked from commit 8d00175f)