[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 5 commits: This patch addresses the exponential blow-up in the simplifier.

Tue Jul 28 06:33:49 UTC 2020

 Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC

Commits:
0bd60059 by Simon Peyton Jones at 2020-07-28T02:01:49-04:00
This patch addresses the exponential blow-up in the simplifier.

Specifically:
  #13253 exponential inlining
  #10421 ditto
  #18140 strict constructors
  #18282 another nested-function call case

This patch makes one really significant changes: change the way that
mkDupableCont handles StrictArg.  The details are explained in
GHC.Core.Opt.Simplify Note [Duplicating StrictArg].

Specific changes

* In mkDupableCont, when making auxiliary bindings for the other arguments
  of a call, add extra plumbing so that we don't forget the demand on them.
  Otherwise we haev to wait for another round of strictness analysis. But
  actually all the info is to hand.  This change affects:
  - Make the strictness list in ArgInfo be [Demand] instead of [Bool],
    and rename it to ai_dmds.
  - Add as_dmd to ValArg
  - Simplify.makeTrivial takes a Demand
  - mkDupableContWithDmds takes a [Demand]

There are a number of other small changes

1. For Ids that are used at most once in each branch of a case, make
   the occurrence analyser record the total number of syntactic
   occurrences.  Previously we recorded just OneBranch or
   MultipleBranches.

   I thought this was going to be useful, but I ended up barely
   using it; see Note [Note [Suppress exponential blowup] in
   GHC.Core.Opt.Simplify.Utils

   Actual changes:
     * See the occ_n_br field of OneOcc.
     * postInlineUnconditionally

2. I found a small perf buglet in SetLevels; see the new
   function GHC.Core.Opt.SetLevels.hasFreeJoin

3. Remove the sc_cci field of StrictArg.  I found I could get
   its information from the sc_fun field instead.  Less to get
   wrong!

4. In ArgInfo, arrange that ai_dmds and ai_discs have a simpler
   invariant: they line up with the value arguments beyond ai_args
   This allowed a bit of nice refactoring; see isStrictArgInfo,
   lazyArgcontext, strictArgContext

There is virtually no difference in nofib. (The runtime numbers
are bogus -- I tried a few manually.)

        Program           Size    Allocs   Runtime   Elapsed  TotalMem
--------------------------------------------------------------------------------
            fft          +0.0%     -2.0%    -48.3%    -49.4%      0.0%
     multiplier          +0.0%     -2.2%    -50.3%    -50.9%      0.0%
--------------------------------------------------------------------------------
            Min          -0.4%     -2.2%    -59.2%    -60.4%      0.0%
            Max          +0.0%     +0.1%     +3.3%     +4.9%      0.0%
 Geometric Mean          +0.0%     -0.0%    -33.2%    -34.3%     -0.0%

Test T18282 is an existing example of these deeply-nested strict calls.
We get a big decrease in compile time (-85%) because so much less
inlining takes place.

Metric Decrease:
    T18282

- - - - -
6ee07b49 by Sylvain Henry at 2020-07-28T02:02:27-04:00
Bignum: add support for negative shifts (fix #18499)

shiftR/shiftL support negative arguments despite Haskell 2010 report
saying otherwise. We explicitly test for negative values which is bad
(it gets in the way of constant folding, etc.). Anyway, for consistency
we fix Bits instancesof Integer/Natural.

- - - - -
f305bbfd by Peter Trommler at 2020-07-28T02:03:02-04:00
config: Fix Haskell platform constructor w/ params

Fixes #18505

- - - - -
4ee614a7 by Oleg Grenrus at 2020-07-28T02:33:46-04:00
Fix typo in haddock

Spotted by `vilpan` on `#haskell`

- - - - -
37ba5283 by Simon Peyton Jones at 2020-07-28T02:33:46-04:00
Remove an incorrect WARN in extendLocalRdrEnv

I noticed this warning going off, and discovered that it's
really fine.  This small patch removes the warning, and docments
what is going on.

- - - - -

30 changed files:

- aclocal.m4
- compiler/GHC/Core/Coercion.hs
- compiler/GHC/Core/Opt/OccurAnal.hs
- compiler/GHC/Core/Opt/SetLevels.hs
- compiler/GHC/Core/Opt/Simplify.hs
- compiler/GHC/Core/Opt/Simplify/Utils.hs
- compiler/GHC/Core/SimpleOpt.hs
- compiler/GHC/Rename/Pat.hs
- compiler/GHC/Types/Basic.hs
- compiler/GHC/Types/Demand.hs
- compiler/GHC/Types/Id/Info.hs
- compiler/GHC/Types/Name/Reader.hs
- libraries/base/Data/Bits.hs
- libraries/base/GHC/IO.hs
- testsuite/tests/numeric/should_compile/T14465.stdout
- testsuite/tests/numeric/should_compile/T7116.stdout
- + testsuite/tests/numeric/should_run/T18499.hs
- + testsuite/tests/numeric/should_run/T18499.stdout
- testsuite/tests/numeric/should_run/all.T
- + testsuite/tests/perf/compiler/T10421.hs
- + testsuite/tests/perf/compiler/T10421_Form.hs
- + testsuite/tests/perf/compiler/T10421_Y.hs
- + testsuite/tests/perf/compiler/T10421a.hs
- + testsuite/tests/perf/compiler/T10421a_Form.hs
- + testsuite/tests/perf/compiler/T13253-spj.hs
- + testsuite/tests/perf/compiler/T13253.hs
- + testsuite/tests/perf/compiler/T18140.hs
- testsuite/tests/perf/compiler/all.T
- testsuite/tests/simplCore/should_compile/T13143.stderr
- testsuite/tests/simplCore/should_compile/T15631.stdout

The diff was not included because it is too large.

View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6dd2d0fad175b421a82a1121e0b86f46ee7d2eed...37ba5283db32b5cae501728e2021d3f7a042a730

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6dd2d0fad175b421a82a1121e0b86f46ee7d2eed...37ba5283db32b5cae501728e2021d3f7a042a730
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