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as they (especially their id info with absence information) clutter the
output too much. They come back with debug_on.

Differential Revision: https://phabricator.haskell.org/D2072

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1933

We also need to update `stgBindHasCafRefs` assertion with this change,
as we no longer have the pre-computed SRT, LiveVars etc. We rename it to
`topStgBindHasCafRefs` and implement it like this:

A non-updatable top-level binding may refer to a CAF by referring to a
top-level definition with CAFs. A top-level definition may have CAFs if
it's updatable. At this point (because this is done after TidyPgm)
top-level Ids (whether imported or defined in this module) are
GlobalIds, so the top-levelness test is easy. (see also comments in the
code)

Reviewers: bgamari, simonpj, austin

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1889

GHC Trac Issues: #11550

This reverts commit 4f9967aa.

Also remove the functions and types that became useless after removing
the fields:

- SRT functions
- LiveInfo type and functions
- freeVarsToLiveVars
- unariseLives and unariseSRT

Reviewers: bgamari, simonpj, austin

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1880

Summary:
In the past the canonical way for constructing an SDoc string literal was the
composition `ptext . sLit`.  But for some time now we have function `text` that
does the same.  Plus it has some rules that optimize its runtime behaviour.
This patch takes all uses of `ptext . sLit` in the compiler and replaces them
with calls to `text`.  The main benefits of this patch are clener (shorter) code
and less dependencies between module, because many modules now do not need to
import `FastString`.  I don't expect any performance benefits - we mostly use
SDocs to report errors and it seems there is little to be gained here.

Test Plan: ./validate

Reviewers: bgamari, austin, goldfire, hvr, alanz

Subscribers: goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D1784

Reviewed By: bgamari, austin

Differential Revision: https://phabricator.haskell.org/D1560

(Simplifier and desugarer do this already)

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1395

This is basically just about continuing maintaining source notes after
the Core stage. Unfortunately, this is more involved as it might seem,
as there are more restrictions on where ticks are allowed to show up.

Notes:

* We replace the StgTick / StgSCC constructors with a unified StgTick
  that can carry any tickish.

* For handling constructor or lambda applications, we generally float
  ticks out.

* Note that thanks to the NonLam placement, we know that source notes
  can never appear on lambdas. This means that as long as we are
  careful to always use mkTick, we will never violate CorePrep
  invariants.

* This is however not automatically true for eta expansion, which
  needs to somewhat awkwardly strip, then re-tick the expression in
  question.

* Where CorePrep floats out lets, we make sure to wrap them in the
  same spirit as FloatOut.

* Detecting selector thunks becomes a bit more involved, as we can run
  into ticks at multiple points.

(From Phabricator D169)

Signed-off-by: Austin Seipp <austin@well-typed.com>

In some cases, the layout of the LANGUAGE/OPTIONS_GHC lines has been
reorganized, while following the convention, to

- place `{-# LANGUAGE #-}` pragmas at the top of the source file, before
  any `{-# OPTIONS_GHC #-}`-lines.

- Moreover, if the list of language extensions fit into a single
  `{-# LANGUAGE ... -#}`-line (shorter than 80 characters), keep it on one
  line. Otherwise split into `{-# LANGUAGE ... -#}`-lines for each
  individual language extension. In both cases, try to keep the
  enumeration alphabetically ordered.
  (The latter layout is preferable as it's more diff-friendly)

While at it, this also replaces obsolete `{-# OPTIONS ... #-}` pragma
occurences by `{-# OPTIONS_GHC ... #-}` pragmas.

There's now an internal -dll-split flag, which we use to tell GHC how
the GHC package is split into 2 separate DLLs. This is used by
Packages.isDllName to determine whether a call is within the same
DLL, or whether it is a call to another DLL.

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

Mostly d -> g (matching DynFlag -> GeneralFlag).
Also renamed if* to when*, matching the Haskell if/when names

All the flags that 'ways' imply are now dynamic

By using Haskell's debugIsOn rather than CPP's "#ifdef DEBUG", we
don't need to kludge things to keep the warning checker happy etc.

This is done by a 'unarisation' pre-pass at the STG level which
translates away all (live) binders binding something of unboxed
tuple type.

This has the following knock-on effects:
  * The subkind hierarchy is vastly simplified (no UbxTupleKind or ArgKind)
  * Various relaxed type checks in typechecker, 'foreign import prim' etc
  * All case binders may be live at the Core level

We only use it for "compiler" sources, i.e. not for libraries.
Many modules have a -fno-warn-tabs kludge for now.

User visible changes
====================

Profilng
--------

Flags renamed (the old ones are still accepted for now):

  OLD            NEW
  ---------      ------------
  -auto-all      -fprof-auto
  -auto          -fprof-exported
  -caf-all       -fprof-cafs

New flags:

  -fprof-auto              Annotates all bindings (not just top-level
                           ones) with SCCs

  -fprof-top               Annotates just top-level bindings with SCCs

  -fprof-exported          Annotates just exported bindings with SCCs

  -fprof-no-count-entries  Do not maintain entry counts when profiling
                           (can make profiled code go faster; useful with
                           heap profiling where entry counts are not used)

Cost-centre stacks have a new semantics, which should in most cases
result in more useful and intuitive profiles.  If you find this not to
be the case, please let me know.  This is the area where I have been
experimenting most, and the current solution is probably not the
final version, however it does address all the outstanding bugs and
seems to be better than GHC 7.2.

Stack traces
------------

+RTS -xc now gives more information.  If the exception originates from
a CAF (as is common, because GHC tends to lift exceptions out to the
top-level), then the RTS walks up the stack and reports the stack in
the enclosing update frame(s).

Result: +RTS -xc is much more useful now - but you still have to
compile for profiling to get it.  I've played around a little with
adding 'head []' to GHC itself, and +RTS -xc does pinpoint the problem
quite accurately.

I plan to add more facilities for stack tracing (e.g. in GHCi) in the
future.

Coverage (HPC)
--------------

 * derived instances are now coloured yellow if they weren't used
 * likewise record field names
 * entry counts are more accurate (hpc --fun-entry-count)
 * tab width is now correct (markup was previously off in source with
   tabs)

Internal changes
================

In Core, the Note constructor has been replaced by

        Tick (Tickish b) (Expr b)

which is used to represent all the kinds of source annotation we
support: profiling SCCs, HPC ticks, and GHCi breakpoints.

Depending on the properties of the Tickish, different transformations
apply to Tick.  See CoreUtils.mkTick for details.

Tickets
=======

This commit closes the following tickets, test cases to follow:

  - Close #2552: not a bug, but the behaviour is now more intuitive
    (test is T2552)

  - Close #680 (test is T680)

  - Close #1531 (test is result001)

  - Close #949 (test is T949)

  - Close #2466: test case has bitrotted (doesn't compile against current
    version of vector-space package)

See the paper "Practical aspects of evidence based compilation in System FC"

* Coercion becomes a data type, distinct from Type

* Coercions become value-level things, rather than type-level things,
  (although the value is zero bits wide, like the State token)
  A consequence is that a coerion abstraction increases the arity by 1
  (just like a dictionary abstraction)

* There is a new constructor in CoreExpr, namely Coercion, to inject
  coercions into terms

The problem arose with this kind of thing

   x = (,) (scc "blah" Nothing)

Then 'x' is marked NoCafRefs by CoreTidy, becuase it has 
arity 1, and doesn't mention any caffy things.

That in turns means that CorePrep must not float out the
sat binding to give

  sat = scc "blah" Nothing
  x = (,) sat

Rather we must generate

  x = \eta. let sat = scc "blah" Nothing 
            in (,) sat eta

URGH! This Caf stuff is such a mess.

It adds a third case to StgOp which already hold StgPrimOp and StgFCallOp.
The code generation for the new StgPrimCallOp case is almost exactly the
same as for out-of-line primops. They now share the tailCallPrim function.
In the Core -> STG translation we map foreign calls using the "prim"
calling convention to the StgPrimCallOp case. This is because in Core we
represent prim calls using the ForeignCall stuff. At the STG level however
the prim calls are really much more like primops than foreign calls.

Modules that need it import it themselves instead.

This required moving PackageId from PackageConfig to Module