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DEC: support functions with more then 62 arguments (copy #1727) #1730

Merged
merged 5 commits into from
Mar 27, 2021
Merged

DEC: support functions with more then 62 arguments (copy #1727) #1730

merged 5 commits into from
Mar 27, 2021

Commits on Mar 27, 2021

  1. clash-dev: enable DEBUG flag 

    (cherry picked from commit f7a4325)
    @leonschoorl
    leonschoorl authored and mergify-bot committed Mar 27, 2021
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  2. DEC: Don't generates pointless cases for shared global arguments 

    Given
    topEntity :: Bool -> Bool -> Bool
    topEntity b x = case b of
        False -> f x False
        True  -> f x True

    f :: Eq a => a -> a -> Bool
    f = ...

DEC would do:
    Changes when applying rewrite to:
    case b[LocalId] of
      False  ->
        f[GlobalId] @Bool $fEqBool[GlobalId] x[LocalId]
          False
      True  ->
        f[GlobalId] @Bool $fEqBool[GlobalId] x[LocalId]
          True
    Result:
    letrec
      c$fOut :: Bool
      = f[GlobalId] @Bool
          (case b[LocalId] of
             False  ->
               $fEqBool[GlobalId]
             True  ->
               $fEqBool[GlobalId])
          x[LocalId]
          (case b[LocalId] of
             False  ->
               False
             True  ->
               True)
    in case b[LocalId] of
         False  ->
           c$fOut[LocalId]
         True  ->
           c$fOut[LocalId]

Because both f's gets the same x argument, in the result the single f
gets the x directly.
But this sharing only worked for LocalId's, for GlobalId's like the
$fEqBool(Eq class dictionary), but clash generates as argument to the
new f:
          (case b[LocalId] of
             False  ->
               $fEqBool[GlobalId]
             True  ->
               $fEqBool[GlobalId])

With this patch we now generate:
    letrec
      c$fOut :: Bool
      = f[GlobalId] @Bool $fEqBool[GlobalId]
          x[LocalId]
          (case b[LocalId] of
             False  ->
               False
             True  ->
               True)
    in case b[LocalId] of
         False  ->
           c$fOut[LocalId]
         True  ->
           c$fOut[LocalId]

(cherry picked from commit c5be58b)
    @leonschoorl
    leonschoorl authored and mergify-bot committed Mar 27, 2021
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  3. Don't hardcode the max tuple size 

    GHC's max tuple size has been 62 for a long time, but on master it is now increased to 64.

https://gitlab.haskell.org/ghc/ghc/-/commit/6e5a83bb6052f9e251a54026294c87a5bd650c93?merge_request_iid=4146
(cherry picked from commit 2c88533)
    @leonschoorl
    leonschoorl authored and mergify-bot committed Mar 27, 2021
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  4. DEC: Split out mkTup, mkTupTy and mkTupSelector 

    So in the next commit we can easily make wrappers around them for big tuples (>62 elements).

(cherry picked from commit d2df1b2)
    @leonschoorl
    leonschoorl authored and mergify-bot committed Mar 27, 2021
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  5. DEC: support functions with more then 62 arguments 

    All (non-shared) arguments to DEC'ed functions are combined into tuples,
so they can all be defined via a single case expression.
But because GHC's tuples are limited to 62 elements, this fails for functions with many arguments.

This patch uses GHC's mkChunkified to create (2-levels of) nested tuples for a maximum of 62^2=3844 arguments.

Fixes #1669

(cherry picked from commit 28b9a57)
    @leonschoorl
    leonschoorl authored and mergify-bot committed Mar 27, 2021
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