[Git][ghc/ghc][master] Fix a buglet in Simplify.simplCast
Marge Bot
gitlab at gitlab.haskell.org
Wed Jun 24 02:49:41 UTC 2020
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
181516bc by Simon Peyton Jones at 2020-06-23T22:49:33-04:00
Fix a buglet in Simplify.simplCast
This bug, revealed by #18347, is just a missing update to
sc_hole_ty in simplCast. I'd missed a code path when I
made the recentchanges in
commit 6d49d5be904c0c01788fa7aae1b112d5b4dfaf1c
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date: Thu May 21 12:53:35 2020 +0100
Implement cast worker/wrapper properly
The fix is very easy.
Two other minor changes
* Tidy up in SimpleOpt.simple_opt_expr. In fact I think this is an
outright bug, introduced in the fix to #18112: we were simplifying
the same coercion twice *with the same substitution*, which is just
wrong. It'd be a hard bug to trigger, so I just fixed it; less code
too.
* Better debug printing of ApplyToVal
- - - - -
5 changed files:
- compiler/GHC/Core/Opt/Simplify.hs
- compiler/GHC/Core/Opt/Simplify/Utils.hs
- compiler/GHC/Core/SimpleOpt.hs
- + testsuite/tests/simplCore/should_compile/T18347.hs
- testsuite/tests/simplCore/should_compile/all.T
Changes:
=====================================
compiler/GHC/Core/Opt/Simplify.hs
=====================================
@@ -1456,7 +1456,8 @@ simplCast env body co0 cont0
= {-#SCC "addCoerce-pushCoValArg" #-}
do { tail' <- addCoerceM m_co2 tail
; if isReflCo co1
- then return (cont { sc_cont = tail' })
+ then return (cont { sc_cont = tail'
+ , sc_hole_ty = coercionLKind co })
-- Avoid simplifying if possible;
-- See Note [Avoiding exponential behaviour]
else do
=====================================
compiler/GHC/Core/Opt/Simplify/Utils.hs
=====================================
@@ -221,9 +221,10 @@ instance Outputable SimplCont where
ppr (TickIt t cont) = (text "TickIt" <+> ppr t) $$ ppr cont
ppr (ApplyToTy { sc_arg_ty = ty, sc_cont = cont })
= (text "ApplyToTy" <+> pprParendType ty) $$ ppr cont
- ppr (ApplyToVal { sc_arg = arg, sc_dup = dup, sc_cont = cont })
- = (text "ApplyToVal" <+> ppr dup <+> pprParendExpr arg)
- $$ ppr cont
+ ppr (ApplyToVal { sc_arg = arg, sc_dup = dup, sc_cont = cont, sc_hole_ty = hole_ty })
+ = (hang (text "ApplyToVal" <+> ppr dup <+> text "hole" <+> ppr hole_ty)
+ 2 (pprParendExpr arg))
+ $$ ppr cont
ppr (StrictBind { sc_bndr = b, sc_cont = cont })
= (text "StrictBind" <+> ppr b) $$ ppr cont
ppr (StrictArg { sc_fun = ai, sc_cont = cont })
=====================================
compiler/GHC/Core/SimpleOpt.hs
=====================================
@@ -213,6 +213,7 @@ simple_opt_expr env expr
in_scope = substInScope subst
in_scope_env = (in_scope, simpleUnfoldingFun)
+ ---------------
go (Var v)
| Just clo <- lookupVarEnv (soe_inl env) v
= simple_opt_clo env clo
@@ -221,17 +222,10 @@ simple_opt_expr env expr
go (App e1 e2) = simple_app env e1 [(env,e2)]
go (Type ty) = Type (substTy subst ty)
- go (Coercion co) = Coercion (optCoercion (soe_dflags env) (getTCvSubst subst) co)
+ go (Coercion co) = Coercion (go_co co)
go (Lit lit) = Lit lit
go (Tick tickish e) = mkTick (substTickish subst tickish) (go e)
- go (Cast e co) = case go e of
- -- flatten nested casts before calling the coercion optimizer;
- -- see #18112 (note that mkCast handles dropping Refl coercions)
- Cast e' co' -> mkCast e' (opt_co (mkTransCo co' co))
- e' -> mkCast e' (opt_co co)
- where
- opt_co = optCoercion (soe_dflags env) (getTCvSubst subst)
-
+ go (Cast e co) = mk_cast (go e) (go_co co)
go (Let bind body) = case simple_opt_bind env bind NotTopLevel of
(env', Nothing) -> simple_opt_expr env' body
(env', Just bind) -> Let bind (simple_opt_expr env' body)
@@ -266,6 +260,9 @@ simple_opt_expr env expr
e' = go e
(env', b') = subst_opt_bndr env b
+ ----------------------
+ go_co co = optCoercion (soe_dflags env) (getTCvSubst subst) co
+
----------------------
go_alt env (con, bndrs, rhs)
= (con, bndrs', simple_opt_expr env' rhs)
@@ -285,6 +282,15 @@ simple_opt_expr env expr
bs = reverse bs'
e' = simple_opt_expr env e
+mk_cast :: CoreExpr -> CoercionR -> CoreExpr
+-- Like GHC.Core.Utils.mkCast, but does a full reflexivity check.
+-- mkCast doesn't do that because the Simplifier does (in simplCast)
+-- But in SimpleOpt it's nice to kill those nested casts (#18112)
+mk_cast (Cast e co1) co2 = mk_cast e (co1 `mkTransCo` co2)
+mk_cast (Tick t e) co = Tick t (mk_cast e co)
+mk_cast e co | isReflexiveCo co = e
+ | otherwise = Cast e co
+
----------------------
-- simple_app collects arguments for beta reduction
simple_app :: SimpleOptEnv -> InExpr -> [SimpleClo] -> CoreExpr
=====================================
testsuite/tests/simplCore/should_compile/T18347.hs
=====================================
@@ -0,0 +1,10 @@
+module T18347 (function) where
+
+import Data.Coerce
+
+newtype All = All Bool
+
+data Encoding = Encoding (Char -> Bool)
+
+function :: Encoding -> Char -> All
+function enc v = coerce (case enc of Encoding x -> x) v
=====================================
testsuite/tests/simplCore/should_compile/all.T
=====================================
@@ -328,3 +328,4 @@ test('T18231', [ only_ways(['optasm']), grep_errmsg(r'^[\w\.]+ ::.*->.*') ], com
# Cast WW
test('T17673', [ only_ways(['optasm']), grep_errmsg(r'^\w+\.\$wf') ], compile, ['-ddump-simpl -dsuppress-uniques -dppr-cols=9999'])
test('T18078', [ only_ways(['optasm']), grep_errmsg(r'^\w+\.\$wf') ], compile, ['-ddump-simpl -dsuppress-uniques -dppr-cols=9999'])
+test('T18347', normal, compile, ['-dcore-lint -O'])
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/181516bcd6f18f22e1df3915bfca0c36524a725b
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/181516bcd6f18f22e1df3915bfca0c36524a725b
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