1. 19 Mar, 2018 1 commit
    • Matthew Pickering's avatar
      Add -flate-specialise which runs a later specialisation pass · afad5561
      Matthew Pickering authored
      Runs another specialisation pass towards the end of the optimisation
      pipeline. This can catch specialisation opportunities which arose from
      the previous specialisation pass or other inlining.
      
      You might want to use this if you are you have a type class method
      which returns a constrained type. For example, a type class where one
      of the methods implements a traversal.
      
      It is not enabled by default or any optimisation level. Only by
      manually enabling the flag `-flate-specialise`.
      
      Reviewers: bgamari
      
      Reviewed By: bgamari
      
      Subscribers: rwbarton, thomie, carter
      
      Differential Revision: https://phabricator.haskell.org/D4457
      afad5561
  2. 26 Jan, 2018 1 commit
    • Matthías Páll Gissurarson's avatar
      Sort valid substitutions for typed holes by "relevance" · cbdea959
      Matthías Páll Gissurarson authored
      This is an initial attempt at tackling the issue of how to order the
      suggestions provided by the valid substitutions checker, by sorting
      them by creating a graph of how they subsume each other. We'd like to
      order them in such a manner that the most "relevant" suggestions are
      displayed first, so that the suggestion that the user might be looking
      for is displayed before more far-fetched suggestions (and thus also
      displayed when they'd otherwise be cut-off by the
      `-fmax-valid-substitutions` limit). The previous ordering was based on
      the order in which the elements appear in the list of imports, which I
      believe is less correlated with relevance than this ordering.
      
      A drawback of this approach is that, since we now want to sort the
      elements, we can no longer "bail out early" when we've hit the
      `-fmax-valid-substitutions` limit.
      
      Reviewers: bgamari, dfeuer
      
      Reviewed By: dfeuer
      
      Subscribers: dfeuer, rwbarton, thomie, carter
      
      Differential Revision: https://phabricator.haskell.org/D4326
      cbdea959
  3. 03 Nov, 2017 1 commit
  4. 29 Oct, 2017 1 commit
    • Joachim Breitner's avatar
      Implement a dedicated exitfication pass #14152 · 0e953da1
      Joachim Breitner authored
      The idea is described in #14152, and can be summarized: Float the exit
      path out of a joinrec, so that the simplifier can do more with it.
      See the test case for a nice example.
      
      The floating goes against what the simplifier usually does, hence we
      need to be careful not inline them back.
      
      The position of exitification in the pipeline was chosen after a small
      amount of experimentation, but may need to be improved. For example,
      exitification can allow rewrite rules to fire, but for that it would
      have to happen before the `simpl_phases`.
      
      Perf.haskell.org reports these nice performance wins:
      
          Nofib allocations
          fannkuch-redux    78446640  - 99.92%      64560
          k-nucleotide     109466384  - 91.32%    9502040
          simple            72424696  -  5.96%   68109560
      
          Nofib instruction counts
          fannkuch-redux  1744331636  -  3.86% 1676999519
          k-nucleotide    2318221965  -  6.30% 2172067260
          scs             1978470869  -  3.35% 1912263779
          simple           669858104  -  3.38%  647206739
          spectral-norm    186423292  -  5.37%  176411536
      
      Differential Revision: https://phabricator.haskell.org/D3903
      0e953da1
  5. 25 Oct, 2017 1 commit
  6. 19 Aug, 2017 1 commit
    • patrickdoc's avatar
      users_guide: Convert mkUserGuidePart generation to a Sphinx extension · cf8ab1ce
      patrickdoc authored
      This removes all dependencies the users guide had on `mkUserGuidePart`.
      The generation of the flag reference table and the various pieces of the
      man page is now entirely contained within the Spinx extension
      `flags.py`. You can see the man page generation on the orphan page
      https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghc.html
      
      The extension works by collecting all of the meta-data attached to the
      `ghc-flag` directives and then formatting and displaying it at
      `flag-print` directives. There is a single printing directive that can
      be customized with two options, what format to display (table, list, or
      block of flags) and an optional category to limit the output to
      (verbosity, warnings, codegen, etc.).
      
      New display formats can be added by creating a function
      `generate_flag_xxx` (where `xxx` is a description of the format) which
      takes a list of flags and a category and returns a new `xxx`. Then just
      add a reference in the dispatch table `handlers`. That display can now
      be run by passing `:type: xxx` to the `flag-print` directive.
      
      `flags.py` contains two maps of settings that can be adjusted. The first
      is a canonical list of flag categories, and the second sets default
      categories for files.
      
      The only functionality that Sphinx could not replace was the
      `what_glasgow_exts_does.gen.rst` file. `mkUserGuidePart` actually just
      reads the list of flags from `compiler/main/DynFlags.hs` which Sphinx
      cannot do. As the flag is deprecated, I added the list as a static file
      which can be updated manually.
      
      Additionally, this patch updates every single documented flag with the
      data from `mkUserGuidePart` to generate the reference table.
      
      Fixes #11654 and, incidentally, #12155.
      
      Reviewers: austin, bgamari
      
      Subscribers: rwbarton, thomie
      
      GHC Trac Issues: #11654, #12155
      
      Differential Revision: https://phabricator.haskell.org/D3839
      cf8ab1ce
  7. 23 Jul, 2017 1 commit
    • patrickdoc's avatar
      users-guide: Standardize and repair all flag references · 44b090be
      patrickdoc authored
      This patch does three things:
      
      1.) It simplifies the flag parsing code in `conf.py` to properly display
      flag definitions created by `.. (ghc|rts)-flag::`. Additionally, all flag
      references must include the associated arguments. Documentation has been
      added to `editing-guide.rst` to explain this.
      
      2.) It normalizes all flag definitions to a similar format. Notably, all
      instances of `<>` have been replaced with `⟨⟩`. All references across the
      users guide have been updated to match.
      
      3.) It fixes a couple issues with the flag reference table's generation code,
      which did not handle comma separated flags in the same cell and did not
      properly reference flags with arguments.
      
      Test Plan:
      `SPHINXOPTS = -n` to activate "nitpicky" mode, which reports all broken
      references. All remaining errors are references to flags without any
      documentation.
      
      Reviewers: austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: rwbarton, thomie
      
      GHC Trac Issues: #13980
      
      Differential Revision: https://phabricator.haskell.org/D3778
      44b090be
  8. 19 Jul, 2017 1 commit
    • Takenobu Tani's avatar
      Fix links to SPJ’s papers (fixes #12578) · 1ed41a74
      Takenobu Tani authored
      This fixes #12578.
      Update links to SPJ's papers in following files:
      
        * compiler/coreSyn/CoreSyn.hs
        * docs/users_guide/using-optimisation.rst
        * docs/users_guide/parallel.rst
        * docs/users_guide/glasgow_exts.rst
      
      This commit is for ghc-8.2 branch.
      
      Test Plan: build
      
      Reviewers: austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: rwbarton, thomie
      
      GHC Trac Issues: #12578
      
      Differential Revision: https://phabricator.haskell.org/D3745
      1ed41a74
  9. 08 Jun, 2017 1 commit
  10. 23 May, 2017 1 commit
  11. 08 May, 2017 1 commit
  12. 29 Mar, 2017 1 commit
    • Matthías Páll Gissurarson's avatar
      Show valid substitutions for typed holes · 26c95f46
      Matthías Páll Gissurarson authored
      The idea is to implement a mechanism similar to PureScript, where they
      suggest which identifiers in scope would fit the given hole. In
      PureScript, they use subsumption (which is what we would like here as
      well). For subsumption, we would have to check each type in scope
      whether the hole is a subtype of the given type, but that would require
      `tcSubType` and constraint satisfiability checking. Currently,
      `TcSimplify` uses a lot of functions from `TcErrors`, so that would
      require more of a rewrite, I will hold on with that for now, and submit
      the more simpler type equality version.
      
      As an example, consider
      
      ```
      ps :: String -> IO ()
      ps = putStrLn
      
      ps2 :: a -> IO ()
      ps2 _ = putStrLn "hello, world"
      
      main :: IO ()
      main = _ "hello, world"
      ```
      
      The results would be something like
      
      ```
          • Found hole: _ :: [Char] -> IO ()
          • In the expression: _
            In a stmt of a 'do' block: _ "hello, world"
            In the expression:
              do _ "hello, world"
          • Relevant bindings include
              main :: IO () (bound at test.hs:13:1)
              ps :: String -> IO () (bound at test.hs:7:1)
              ps2 :: forall a. a  -> IO () (bound at test.hs:10:1)
            Valid substitutions include
              putStrLn :: String
                          -> IO () (imported from ‘Prelude’ at
      test.hs:1:1-14
                                    (and originally defined in
      ‘System.IO’))
              putStr :: String
                        -> IO () (imported from ‘Prelude’ at
      test.hs:1:1-14
                                  (and originally defined in ‘System.IO’))
      ```
      
      We'd like here for ps2 to be suggested as well, but for that we require
      subsumption.
      
      Reviewers: austin, bgamari, dfeuer, mpickering
      
      Reviewed By: dfeuer, mpickering
      
      Subscribers: mpickering, Wizek, dfeuer, rwbarton, thomie
      
      Differential Revision: https://phabricator.haskell.org/D3361
      26c95f46
  13. 27 Mar, 2017 1 commit
  14. 19 Mar, 2017 1 commit
  15. 27 Feb, 2017 1 commit
    • Simon Peyton Jones's avatar
      Add -fspec-constr-keen · 4f38fa10
      Simon Peyton Jones authored
      I discovered that the dramatic imprvoement in perf/should_run/T9339
      with the introduction of join points was really rather a fluke, and
      very fragile.
      
      The real problem (see Note [Making SpecConstr keener]) is that
      SpecConstr wasn't specialising a function even though it was applied
      to a freshly-allocated constructor.  The paper describes plausible
      reasons for this, but I think it may well be better to be a bit more
      aggressive.
      
      So this patch add -fspec-constr-keen, which makes SpecConstr a bit
      keener to specialise, by ignoring whether or not the argument
      corresponding to a call pattern is scrutinised in the function body.
      Now the gains in T9339 should be robust; and it might even be a
      better default.
      
      I'd be interested in what happens if we switched on -fspec-constr-keen
      with -O2.
      
      Reviewers: austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D3186
      4f38fa10
  16. 08 Feb, 2017 1 commit
  17. 31 Jan, 2017 1 commit
    • Daniel Haraj's avatar
      Use top-level instances to solve superclasses where possible · 748b7974
      Daniel Haraj authored
      This patch introduces a new flag `-fsolve-constant-dicts` which makes the
      constraint solver solve super class constraints with available dictionaries if
      possible. The flag is enabled by `-O1`.
      
      The motivation of this patch is that the compiler can produce more efficient
      code if the constraint solver used top-level instance declarations to solve
      constraints that are currently solved givens and their superclasses. In
      particular, as it currently stands, the compiler imposes a performance penalty
      on the common use-case where superclasses are bundled together for user
      convenience. The performance penalty applies to constraint synonyms as
      well. This example illustrates the issue:
      
      ```
      {-# LANGUAGE ConstraintKinds, MultiParamTypeClasses, FlexibleContexts #-}
      module B where
      
      class M a b where m :: a -> b
      
      type C a b = (Num a, M a b)
      
      f :: C Int b => b -> Int -> Int
      f _ x = x + 1
      ```
      
      Output without the patch, notice that we get the instance for `Num Int` by
      using the class selector `p1`.
      
      ```
      f :: forall b_arz. C Int b_arz => b_arz -> Int -> Int
      f =
        \ (@ b_a1EB) ($d(%,%)_a1EC :: C Int b_a1EB) _ (eta1_B1 :: Int) ->
          + @ Int
            (GHC.Classes.$p1(%,%) @ (Num Int) @ (M Int b_a1EB) $d(%,%)_a1EC)
            eta1_B1
            B.f1
      ```
      
      Output with the patch, nicely optimised code!
      
      ```
      f :: forall b. C Int b => b -> Int -> Int
      f =
        \ (@ b) _ _ (x_azg :: Int) ->
          case x_azg of { GHC.Types.I# x1_a1DP ->
          GHC.Types.I# (GHC.Prim.+# x1_a1DP 1#)
          }
      ```
      
      Reviewers: simonpj, bgamari, austin
      
      Reviewed By: simonpj
      
      Subscribers: mpickering, rwbarton, thomie
      
      Differential Revision: https://phabricator.haskell.org/D2714
      
      GHC Trac Issues: #12791, #5835
      748b7974
  18. 24 Jan, 2017 1 commit
  19. 05 Jan, 2017 1 commit
    • Joachim Breitner's avatar
      Add a CSE pass to Stg (#9291) · 19d5c731
      Joachim Breitner authored
      This CSE pass only targets data constructor applications. This is
      probably the best we can do, as function calls and primitive operations
      might have side-effects.
      
      Introduces the flag -fstg-cse, enabled by default with -O for now. It
      might also be a good candiate for -O2.
      
      Differential Revision: https://phabricator.haskell.org/D2871
      19d5c731
  20. 09 Dec, 2016 1 commit
    • Sylvain Henry's avatar
      Scrutinee Constant Folding · d3b546b1
      Sylvain Henry authored
      This patch introduces new rules to perform constant folding through
      case-expressions.
      
      E.g.,
      ```
      case t -# 10# of _ {  ===> case t of _ {
               5#      -> e1              15#     -> e1
               8#      -> e2              18#     -> e2
               DEFAULT -> e               DEFAULT -> e
      ```
      
      The initial motivation is that it allows "Merge Nested Cases"
      optimization to kick in and to further simplify the code
      (see Trac #12877).
      
      Currently we recognize the following operations for Word# and Int#: Add,
      Sub, Xor, Not and Negate (for Int# only).
      
      Test Plan: validate
      
      Reviewers: simonpj, austin, bgamari
      
      Reviewed By: simonpj, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2762
      
      GHC Trac Issues: #12877
      d3b546b1
  21. 30 Jun, 2016 1 commit
  22. 17 Apr, 2016 1 commit
    • quchen's avatar
      Add flag to control number of missing patterns in warnings · 7005b9f7
      quchen authored
      Non-exhaustive pattern warnings had their number of patterns to
      show hardcoded in the past. This patch implements the TODO remark
      that this should be made a command line flag.
      
          -fmax-uncovered-patterns=<n>
      
      can now be used to influence the number of patterns to be shown.
      
      Reviewers: hvr, austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2076
      7005b9f7
  23. 30 Mar, 2016 1 commit
  24. 09 Jan, 2016 1 commit
  25. 03 Oct, 2015 1 commit