From 321d1bd8a79ab39c3c9e8697fffb0107c43f83cf Mon Sep 17 00:00:00 2001
From: Sebastian Graf <sebastian.graf@kit.edu>
Date: Tue, 3 Nov 2020 18:28:49 +0100
Subject: [PATCH] Fix strictness signatures of `prefetchValue*#` primops
Their strictness signatures said the primops are strict in their first
argument, which is wrong: Handing it a thunk will prefetch the pointer
to the thunk, but not evaluate it. Hence not strict.
The regression test `T8256` actually tests for laziness in the first
argument, so GHC apparently never exploited the strictness signature.
See also https://gitlab.haskell.org/ghc/ghc/-/issues/8256#note_310867,
where this came up.
---
compiler/GHC/Builtin/primops.txt.pp | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/compiler/GHC/Builtin/primops.txt.pp b/compiler/GHC/Builtin/primops.txt.pp
index acee822b0cf0..74abca2927e3 100644
--- a/compiler/GHC/Builtin/primops.txt.pp
+++ b/compiler/GHC/Builtin/primops.txt.pp
@@ -3519,8 +3519,7 @@ primop PrefetchAddrOp3 "prefetchAddr3#" GenPrimOp
primop PrefetchValueOp3 "prefetchValue3#" GenPrimOp
a -> State# s -> State# s
- with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topDiv }
- has_side_effects = True
+ with has_side_effects = True
----
primop PrefetchByteArrayOp2 "prefetchByteArray2#" GenPrimOp
@@ -3537,8 +3536,7 @@ primop PrefetchAddrOp2 "prefetchAddr2#" GenPrimOp
primop PrefetchValueOp2 "prefetchValue2#" GenPrimOp
a -> State# s -> State# s
- with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topDiv }
- has_side_effects = True
+ with has_side_effects = True
----
primop PrefetchByteArrayOp1 "prefetchByteArray1#" GenPrimOp
@@ -3555,8 +3553,7 @@ primop PrefetchAddrOp1 "prefetchAddr1#" GenPrimOp
primop PrefetchValueOp1 "prefetchValue1#" GenPrimOp
a -> State# s -> State# s
- with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topDiv }
- has_side_effects = True
+ with has_side_effects = True
----
primop PrefetchByteArrayOp0 "prefetchByteArray0#" GenPrimOp
@@ -3573,8 +3570,7 @@ primop PrefetchAddrOp0 "prefetchAddr0#" GenPrimOp
primop PrefetchValueOp0 "prefetchValue0#" GenPrimOp
a -> State# s -> State# s
- with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topDiv }
- has_side_effects = True
+ with has_side_effects = True
------------------------------------------------------------------------
--- ---
--
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