[GHC] #11441: RFC: Inline intermediate languages (Core, STG, Cmm, even StrictCore)

[GHC]

#11441: RFC: Inline intermediate languages (Core, STG, Cmm, even StrictCore)
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        Reporter:  Iceland_jack      |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Iceland_jack):

 Focusing on Core for now, we can reuse Haskell's syntax (some intersection
 between Haskell and Core syntax), see #11350, with minor sugar for
 functions:

 {{{#!hs
 {-# CORE id #-}
 id :: forall a. a -> a
 id @a (x :: a) = x

 {-# CORE add #-}
 double :: forall num. Num num => num -> num
 double (@ num) (numDict :: Num num) (x :: num) =
   (+) (@ num) numDict x x
 }}}

 or we could cheekily reuse Template Haskell. Like
 [https://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields/OverloadedLabels#Syntax
 this suggestions] to define a magic module for implicit values we can have
 define a magic module of quoters (`QuasiQuoter`s for sublanguages that are
 treated specially:

 {{{#!hs
 import GHC.Magic (core, stg)

 [core|
 id :: forall a. a -> a
 id = \ (@ a) (x :: a) -> x

 double :: forall num. Num num => num -> num
 double = \(@ num) (numDict :: Num num) (x :: num) ->
   + @ num numDict x x
 |]
 }}}

 or a combinator library where users code directly in Core AST, `data Expr
 b = Var Id | ...`.

 Some questions:
 * Dictionaries and their scope.
 * Writing function metadata.
 * Only top-level definitions?
 * ...

 Interested in other uses.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11441#comment:5>
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