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`SysTools.Terminal.queryCygwinTerminal` now exists in the `Win32`
library under the name `isMinTTYHandle` since `Win32-2.5.0.0`.
(GHC 8.4.4 ships with `Win32-2.6.1.0`, so this is well within GHC's
support window.) We can therefore get replace `queryCygwinTerminal`
with `isMinTTYHandle` and delete quite a bit of code from
`SysTools.Terminal` in the process.

Along the way I needed to replace some uses of `#if defined x` with
`#if defined(x)` to please the CI linters.

1) FastStrings are always UTF-8 encoded now.
2) Clarify what is meant by "hashed"
3) Add mention of lazy z-enc

Having an IORef in FastString to memoize the z-encoded version is
unecessary because there is this amazing thing Haskell can do natively,
it's called "lazyness" :)

We simply remove the UNPACK and strictness annotations from the constructor
field corresponding to the z-encoding, making it lazy, and store the
(pure) z-encoded string there.

The only complication here is 'hasZEncoding' which allows cheking if a
z-encoding was computed for a given string. Since this is only used for
compiler performance statistics though it's not actually necessary to have
the current per-string granularity.

Instead I add a global IORef counter to the FastStringTable and use
unsafePerformIO to increment the counter whenever a lazy z-encoding is
forced.

Those constructors have been added after GHC 8.8. The version guards
in `binary` are correct, see https://github.com/kolmodin/binary/pull/167/files.

See the user manual entry -- this helps when debugging as generated Core
gets smaller without these bindings.

Mainly we now generate this

    data PlatformConstants = PlatformConstants {
          pc_CONTROL_GROUP_CONST_291 :: Int,
          pc_STD_HDR_SIZE :: Int,
          pc_PROF_HDR_SIZE :: Int,
          pc_BLOCK_SIZE :: Int,
      }

instead of

    data PlatformConstants = PlatformConstants {
        pc_platformConstants :: ()
        , pc_CONTROL_GROUP_CONST_291 :: Int
        , pc_STD_HDR_SIZE :: Int
        , pc_PROF_HDR_SIZE :: Int
        , pc_BLOCK_SIZE :: Int
        ...
      }

The first field has no use and according to (removed) comments it was to
make code generator's work easier.. if anything this version is simpler
because it has less repetition (the commas in strings are gone).

Some where using `True` / `False`, a legacy of when they were in
`Config.hs`. See #16914 / d238d306 for a similar problem.

Also clean up the configure variables names for consistency and clarity
while we're at it. "Target" makes clear we are talking about outputted
code, not where GHC itself runs.

The tightens up the kinds a bit. I use type synnonyms to avoid adding
promotion ticks everywhere.

- Fixes crazy indentation in -ddump-debug output
- We no longer dump empty sections in -ddump-debug when a code block
  does not have any generated debug info
- Minor refactoring in Debug.hs and AsmCodeGen.hs

Define MD5Context in terms of `uint*_t` and don't use `HsFFI.h`.

This special case existed for no reason, and made things inconsistent.

Before

    Boolean.$bT :: Boolean.Boolean
    [GblId, Str=m, Unf=OtherCon []] =
        CAF_ccs  \ u  []  Boolean.$bT1;

After

    Boolean.$bF :: Boolean.Boolean
    [GblId, Str=m, Unf=OtherCon []] =
        \u [] Boolean.$bF1;

The cost-centre is now hidden when not profiling, as is the case with
other types of closures.

Add another small test step

Use the same identifier name in different
scopes and see, if ':uses' handles that.

Add another test step

to check wether local bindings with the
same identifier name might get confused

Add easier to understand test output

Fix annotated lines from file correctly

This patch removes 'userHsLTyVarBndrs' and 'userHsTyVarBndrs' from HsUtils.
These helper functions were not used anywhere.

Before the change ./configure detected numa support automatically
withoun a nice way to disable autodetection.

The change adds `--enable-numa` / `--disable-numa` switch to
override the default. If `--enable-numa` is passed and `libnuma`
is not present then configure will fail.

Reported-by: Sergey Alirzaev
Bug: https://github.com/gentoo-haskell/gentoo-haskell/issues/955Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

Noticed by @simonmar in !1362:

    If the srtEntry is Nothing, then it should be safe to omit
    references to this SRT from other SRTs, even if it is a static
    function.

When updating SRT map we don't omit references to static functions (see
Note [Invalid optimisation: shortcutting]), but there's no reason to add
an SRT entry for a static function if the function is not CAFFY.

(Previously we'd add SRT entries for static functions even when they're
not CAFFY)

Using 9151b99e I checked sizes of all SRTs when building GHC and
containers:

- GHC: 583736 (HEAD), 581695 (this patch). 2041 less SRT entries.
- containers: 2457 (HEAD), 2381 (this patch). 76 less SRT entries.

This was inadvertently referring to the cabal-install-latest/ directory
which is volatile.

There were two problems with LLVM version checking:

- The parser would only parse x and x.y formatted versions. E.g. 1.2.3
  would be rejected.

- The version check was too strict and would reject x.y formatted
  versions. E.g. when we support version 7 it'd reject 7.0 ("LLVM
  version 7.0") and only accept 7 ("LLVM version 7").

We now parse versions with arbitrarily deep minor numbering (x.y.z.t...)
and accept versions as long as the major version matches the supported
version (e.g. 7.1, 7.1.2, 7.1.2.3 ...).

[ci skip]

The `mkOneConFull` function of the pattern match checker used to try to
guess the type arguments of the data type's type constructor by looking
at the ambient type of the match. This doesn't work well for Pattern
Synonyms, where the result type isn't even necessarily a TyCon
application, and it shows in #11336 and #17112.

Also the effort seems futile; why try to try hard when the type checker
has already done the hard lifting? After this patch, we instead supply
the type constructors arguments as an argument to the function and
lean on the type-annotated AST.

This generalizes code generators (outputAsm, outputLlvm, outputC, and
the call site codeOutput) so that they'll return the return values of
the passed Cmm streams.

This allows accumulating data during Cmm generation and returning it to
the call site in HscMain.

Previously the Cmm streams were assumed to return (), so the code
generators returned () as well.

This change is required by !1304 and !1530.

Skipping CI as this was tested before and I only updated the commit
message.

[skip ci]

[skip ci]

Before the change
    ./configure --disable-dwarf-debug
enabled DWARF debugging unconditionally.

This happened due to use of 5-argument form of `AC_ARG_ENABLE`
without actually checking the passed  `$enableval` parameter:

```
AC_ARG_ENABLE(dwarf-unwind,
    [AC_HELP_STRING([--enable-dwarf-unwind],
        [Enable DWARF unwinding support in the runtime system via elfutils' libdw [default=no]])],
    [AC_CHECK_LIB(dw, dwfl_attach_state,
      [UseLibdw=YES],
      [AC_MSG_ERROR([Cannot find system libdw (required by --enable-dwarf-unwind)])])]
    [UseLibdw=NO]
)
```

Note:

- `[UseLibdw=NO]` is called when `--{enable,disable}-dwarf-unwind`
  is not passed at all as a parameter (ok).
- `[AC_CHECK_LIB(dw, dwfl_attach_state, [UseLibdw=YES],` is called
  for both:

  * `--enable-dwarf-unwind` being passed: `$enableval = "yes"` (ok).
  *  --disable-dwarf-unwind` being passed: `$enableval = "no"` (bad).

The change is to use 3-argument `AC_ARG_ENABLE` and check for passed
value as `"$enable_dwarf_unwind" = "yes"`.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

Use LEB128 encoding for Int/Word variants. This reduces
the size of interface files significantly. (~19%).

Also includes a few small optimizations to make unboxing
work better that I have noticed while looking at the core.

This adds a Stream.consume function, uses it in LLVM and C code
generators, and removes the use of Stream.collect function which was
used to collect streaming Cmm generation results into a list.

LLVM and C backends now properly use streamed Cmm generation, instead of
collecting Cmm groups into a list before generating LLVM/C code.

Previously we were using an empty ModuleSRTInfo for each Cmm group with
-split-section. As far as I can see this has no benefits, and
simplifying this makes another patch simpler (!1304).

We also remove some outdated comments: we no longer generate one
module-level SRT.

While avoiding #16943.

This commit adds documentation on Hadrian's 'Expr' type and
references the documentation in hadrian/README.md

We now do a shallow closure check on objects in compact regions.

See the new comment on why we can't do a "normal" closure check.