llvmGen: Compatibility with LLVM 3.5 (re #9142)

Due to changes in LLVM 3.5 aliases now may only refer to definitions.
Previously to handle symbols defined outside of the current commpilation
unit GHC would emit both an `external` declaration, as well as an alias
pointing to it, e.g.,

    @stg_BCO_info = external global i8
    @stg_BCO_info$alias = alias private i8* @stg_BCO_info

Where references to `stg_BCO_info` will use the alias
`stg_BCO_info$alias`. This is not permitted under the new alias
behavior, resulting in errors resembling,

    Alias must point to a definition
    i8* @"stg_BCO_info$alias"

To fix this, we invert the naming relationship between aliases and
definitions. That is, now the symbol definition takes the name
`@stg_BCO_info$def` and references use the actual name, `@stg_BCO_info`.
This means the external symbols can be handled by simply emitting an
`external` declaration,

    @stg_BCO_info = external global i8

Whereas in the case of a forward declaration we emit,

    @stg_BCO_info = alias private i8* @stg_BCO_info$def

Reviewed By: austin

Differential Revision: https://phabricator.haskell.org/D155
Add displayException method to Exception (#9822)

Defaults to using `show` to prevent any breakage of existing code.  Also
provide a custom implementation for `SomeException` which uses the
underlying exception's `displayException`.

Differential Revision: https://phabricator.haskell.org/D517
Add function for size-checked conversion of Integral types

The new function `Data.Bits.toIntegralSized` provides a similar
functionality to `fromIntegral` but adds validation that the
argument fits in the result type's size.

The implementation of `toIntegralSized` has been derived from `intCastMaybe`
(which is part of Herbert Valerio Riedel's `int-cast` package,
see http://hackage.haskell.org/package/int-cast)

Addresses #9816

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D512
ghc: allow --show-options and --interactive together

Summary:
Previously 'ghc --show-options' showed all options that GHC can possibly
accept. With this patch, it'll only show the options that have effect in
non-interactive modes.
This change also adds support for using 'ghc --interactive --show-options'
which previously was disallowed. This command will show all options that have
effect in the interactive mode.
The CmdLineParser is updated to know about the GHC modes, and then each flag
is annotated with which mode it has effect.
This fixes #9259.

Test Plan:
Try out --show-options with --interactive on the command line. With and without
--interactive should give different results.
Run the test suite, mode001 has been updated to verify this new flag
combination.

Reviewers: austin, jstolarek

Reviewed By: austin, jstolarek

Subscribers: jstolarek, thomie, carter, simonmar

Differential Revision: https://phabricator.haskell.org/D337

GHC Trac Issues: #9259
Add -fdefer-typed-holes flag which defers hole errors to runtime.

Summary:
As proposed by Richard on Trac. This patch adds a new flag -fdefer-typed-holes
and changes the semantics of the -fno-warn-typed-holes flag.

To summarise, by default GHC has typed holes enabled and produces a compile
error when it encounters a typed hole.

When -fdefer-type-errors OR -fdefer-typed-holes is enabled, hole errors are
converted to warnings and result in runtime errors when evaluated.

The warning flag -fwarn-typed-holes is on by default. Without -fdefer-type-errors
or -fdefer-typed-holes this flag is a no-op, since typed holes are an error
under these conditions. If either of the defer flags are enabled (converting
typed hole errors into warnings) the -fno-warn-typed-holes flag disables the
warnings. This means compilation silently succeeds and evaluating a hole will
produce a runtime error.

The rationale behind allowing typed holes warnings to be silenced is that tools
like Syntastic for vim highlight warnings and hole warnings may be undesirable.

Signed-off-by: Merijn Verstraaten <merijn@inconsistent.nl>

Test Plan: validate

Reviewers: austin, simonpj, thomie

Reviewed By: simonpj, thomie

Subscribers: Fuuzetsu, thomie, carter

Differential Revision: https://phabricator.haskell.org/D442

GHC Trac Issues: #9497

Conflicts:
	compiler/main/DynFlags.hs
Deprecate Data.Version.versionTags (#2496)

The library submission was accepted:

  http://www.haskell.org/pipermail/libraries/2014-September/023777.html

The T5892ab testcases were changed to use `Data.Tree` instead of `Data.Version`

Reviewed By: ekmett

Differential Revision: https://phabricator.haskell.org/D395
Implement `Natural` number type (re #9818)

This implements a `Natural` type for representing unsigned arbitrary
precision integers.

When available, `integer-gmp>=1.0.0`'s `BigNat` type is used as
building-block to construct `Natural` as an algebraic data-type.
Otherwise, `Natural` falls back being a `newtype`-wrapper around
`Integer` (as is done in Edward Kmett's `nats` package).

The `GHC.Natural` module exposes an internal GHC-specific API, while
`Numeric.Natural` provides the official & portable API.

Reviewed By: austin, ekmett

Differential Revision: https://phabricator.haskell.org/D473
Re-center bytes-allocated for `haddock.compiler`

This should silence the

   perf/haddock  haddock.compiler [stat not good enough] (normal)

test-failure...
Revert "Test Trac #9318"

This reverts commit 5760eb598e0dfa451407195f15072204c15233ed
because the very same test was already added via
5eebd990ea7a5bc1937657b101ae83475e20fc7a and is causing
`./validate` to fail due to "framework failure".
integer-gmp2: export `Word`-counterpart of gcdInt

It's trivial for `integer-gmp2` (#9281) to provide it, and it'll be
useful for a future 'Natural'-related commit, as well as providing a
`Word` optimised `gcd`-RULE.
Remove reference to `MIN_VERSION_integer_gmp2`

This is slipped in by accident as part of
c774b28f76ee4c220f7c1c9fd81585e0e3af0e8a (re #9281)
Add gcd/Word RULE-based optimisation

This makes use of the `gcdWord` primitive provided by
be7fb7e58c70cd9b0a933fb26cd5f2607d6dc4b2 which should make the
`Word`-variant of `gcd` as performant as the `Int`-variant.
Add `isValidNatural` predicate (#9818)

This predicate function encodes the internal `Natural` invariants, and
is useful for testsuites or code that directly constructs `Natural`
values.

C.f. `integer-gmp2`'s `isValidBigNat#` and `isValidInteger#` predicates
for testing internal invariants.
Fix `fromInteger` constructing invalid `Natural`

This fixes a case where `isValidNatural . fromInteger` would be `False`.

Re #9818
Implement {gcd,lcm}/Natural optimisation (#9818)

This provides the equivalent of the existing `{gcd,lcm}/Integer`
optimisations for the `Natural` type, when using the `integer-gmp2`
backend.
Call `popCountBigNat` directly (#9818)

This calls the `popCountBigNat` primitive directly instead of going
through `Integer`'s `popCount`.
Define void using <$ (re #9827)

`() <$ x` is sometimes better than `fmap (const ()) x` and should
never be worse.

Reviewed By: ekmett

Differential Revision: https://phabricator.haskell.org/D521
Add `Storable` instances for `Complex` and `Ratio`

The actual type-signatures of the new instances are:

  instance Storable a => Storable (Complex a)

  instance (Storable a, Integral a) => Storable (Ratio a)

See also

  https://groups.google.com/d/msg/haskell-core-libraries/mjBSo2CQ3LU/0gwg0QvviOIJ

Addresses #9826

Reviewed By: ekmett

Differential Revision: https://phabricator.haskell.org/D519
Install `ghc-gmp.h` C include header file (#9281)

This is mostly interesting when using the in-tree GMP, as there's
no way otherwise to access the in-tree `gmp.h` header file after installation.

In case `integer-gmp2` was build against a system-installed GMP library,
`ghc-gmp.h` simply contains `#include <gmp.h>` for convenience.

Reviewed By: ekmett

Differential Revision: https://phabricator.haskell.org/D522
Persist build-time GMP ver to `HsIntegerGmp.h`

This creates the additional macro definitions in `HsIntegerGmp.h` which
are useful for 3rd party `integer-gmp`-addon libraries.

Here's an example for the definitions created for the in-tree GMP:

  #define GHC_GMP_INTREE     1
  #define GHC_GMP_VERSION_MJ 5
  #define GHC_GMP_VERSION_MI 0
  #define GHC_GMP_VERSION_PL 4
  #define GHC_GMP_VERSION   (5 * 10000 + 0 * 100 + 4)

And here's an example for a system-installed GMP:

  #define GHC_GMP_INTREE     0
  #define GHC_GMP_VERSION_MJ 6
  #define GHC_GMP_VERSION_MI 0
  #define GHC_GMP_VERSION_PL 0
  #define GHC_GMP_VERSION   (6 * 10000 + 0 * 100 + 0)

Part of #9281

Reviewed By: ekmett (via D522)