[Git][ghc/ghc][wip/T17521] 2 commits: Add exception to letrect invariant

[Jaro Reinders (@Noughtmare)]

Jaro Reinders pushed to branch wip/T17521 at Glasgow Haskell Compiler / GHC


Commits:
44bd7b2f by Jaro Reinders at 2023-07-17T15:51:38+02:00
Add exception to letrect invariant

- - - - -
df499b72 by Jaro Reinders at 2023-07-17T15:52:02+02:00
Add stg rewrites test

- - - - -


4 changed files:

- compiler/GHC/Core.hs
- + testsuite/tests/unlifted-datatypes/should_compile/TopLevelStgRewrite.hs
- + testsuite/tests/unlifted-datatypes/should_compile/TopLevelStgRewritea.hs
- testsuite/tests/unlifted-datatypes/should_compile/all.T


Changes:

=====================================
compiler/GHC/Core.hs
=====================================
@@ -377,13 +377,13 @@ for the meaning of "lifted" vs. "unlifted".
 For the non-top-level, non-recursive case see
 Note [Core let-can-float invariant].
 
-At top level, however, there are two exceptions to this rule:
+At top level, however, there are three exceptions to this rule:
 
 (TL1) A top-level binding is allowed to bind primitive string literal,
       (which is unlifted).  See Note [Core top-level string literals].
 
 (TL2) In Core, we generate a top-level binding for every non-newtype data
-constructor worker or wrapper
+      constructor worker or wrapper
       e.g.   data T = MkT Int
       we generate
              MkT :: Int -> T
@@ -399,6 +399,12 @@ constructor worker or wrapper
              S1 = S1
       We allow this top-level unlifted binding to exist.
 
+(TL3) A boxed top-level binding is allowed to bind the application of a data
+      constructor worker to trivial arguments. These bindings are guaranteed
+      to not require any evaluation and can thus be compiled to static data.
+      Unboxed top-level bindings are still not allowed because references
+      to them might have to be pointers.
+
 Note [Core let-can-float invariant]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The let-can-float invariant:


=====================================
testsuite/tests/unlifted-datatypes/should_compile/TopLevelStgRewrite.hs
=====================================
@@ -0,0 +1,17 @@
+{-# OPTIONS_GHC -O #-}
+{-# LANGUAGE UnliftedDatatypes #-}
+
+module TopLevelStgRewrite where
+
+import TopLevelStgRewritea
+import GHC.Exts
+import Data.Kind (Type)
+
+type Box :: UnliftedType -> Type
+data Box a = Box a
+
+type B :: Type -> UnliftedType
+data B a = B !a
+
+b :: Box (B Bool)
+b = Box (B a)


=====================================
testsuite/tests/unlifted-datatypes/should_compile/TopLevelStgRewritea.hs
=====================================
@@ -0,0 +1,6 @@
+{-# OPTIONS_GHC -O0 #-}
+
+module TopLevelStgRewritea where
+
+a :: Bool
+a = True


=====================================
testsuite/tests/unlifted-datatypes/should_compile/all.T
=====================================
@@ -3,3 +3,4 @@ test('UnlDataPolySigs', normal, compile, [''])
 test('UnlDataFams', normal, compile, [''])
 test('UnlDataUsersGuide', normal, compile, [''])
 test('TopLevel', normal, multimod_compile, ['TopLevel', '-O'])
+test('TopLevelStgRewrite', normal, multimod_compile, ['TopLevelStgRewrite', '-v0'])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0891b558ad08124d8e1a53f14fd68805cb02e711...df499b7224175010b63e83a3eb4b0f4db41375f6

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0891b558ad08124d8e1a53f14fd68805cb02e711...df499b7224175010b63e83a3eb4b0f4db41375f6
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