From c929f02bd0a1ff4c474ca18a03ac011d3394e291 Mon Sep 17 00:00:00 2001
From: Sebastian Graf <sebastian.graf@kit.edu>
Date: Fri, 10 Dec 2021 16:59:00 +0100
Subject: [PATCH] CoreSubst: Stricten `substBndr` and `cloneBndr`
Doing so reduced allocations of `cloneBndr` by about 25%.
```
T9233(normal) ghc/alloc 672,488,656 663,083,216 -1.4% GOOD
T9675(optasm) ghc/alloc 423,029,256 415,812,200 -1.7%
geo. mean -0.1%
minimum -1.7%
maximum +0.1%
```
Metric Decrease:
T9233
---
compiler/GHC/Core/Subst.hs | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/compiler/GHC/Core/Subst.hs b/compiler/GHC/Core/Subst.hs
index 757a025db591..20db06f29261 100644
--- a/compiler/GHC/Core/Subst.hs
+++ b/compiler/GHC/Core/Subst.hs
@@ -370,7 +370,7 @@ substIdBndr :: SDoc
substIdBndr _doc rec_subst subst@(Subst in_scope env tvs cvs) old_id
= -- pprTrace "substIdBndr" (doc $$ ppr old_id $$ ppr in_scope) $
- (Subst (in_scope `InScopeSet.extendInScopeSet` new_id) new_env tvs cvs, new_id)
+ (Subst new_in_scope new_env tvs cvs, new_id)
where
id1 = uniqAway in_scope old_id -- id1 is cloned if necessary
id2 | no_type_change = id1
@@ -384,14 +384,16 @@ substIdBndr _doc rec_subst subst@(Subst in_scope env tvs cvs) old_id
-- new_id has the right IdInfo
-- The lazy-set is because we're in a loop here, with
-- rec_subst, when dealing with a mutually-recursive group
- new_id = maybeModifyIdInfo mb_new_info id2
+ !new_id = maybeModifyIdInfo mb_new_info id2
mb_new_info = substIdInfo rec_subst id2 (idInfo id2)
-- NB: unfolding info may be zapped
-- Extend the substitution if the unique has changed
-- See the notes with substTyVarBndr for the delVarEnv
- new_env | no_change = delVarEnv env old_id
- | otherwise = extendVarEnv env old_id (Var new_id)
+ !new_in_scope = in_scope `InScopeSet.extendInScopeSet` new_id
+ -- Forcing new_in_scope improves T9675 by 1.7%
+ !new_env | no_change = delVarEnv env old_id
+ | otherwise = extendVarEnv env old_id (Var new_id)
no_change = id1 == old_id
-- See Note [Extending the IdSubstEnv]
@@ -443,13 +445,15 @@ clone_id :: Subst -- Substitution for the IdInfo
-> (Subst, Id) -- Transformed pair
clone_id rec_subst subst@(Subst in_scope idvs tvs cvs) (old_id, uniq)
- = (Subst (in_scope `InScopeSet.extendInScopeSet` new_id) new_idvs tvs new_cvs, new_id)
+ = (Subst new_in_scope new_idvs tvs new_cvs, new_id)
where
id1 = setVarUnique old_id uniq
id2 = substIdType subst id1
- new_id = maybeModifyIdInfo (substIdInfo rec_subst id2 (idInfo old_id)) id2
- (new_idvs, new_cvs) | isCoVar old_id = (idvs, extendVarEnv cvs old_id (mkCoVarCo new_id))
- | otherwise = (extendVarEnv idvs old_id (Var new_id), cvs)
+ !new_id = maybeModifyIdInfo (substIdInfo rec_subst id2 (idInfo old_id)) id2
+ !new_in_scope = in_scope `InScopeSet.extendInScopeSet` new_id
+ -- Forcing new_in_scope improves T9675 by 1.7%
+ (!new_idvs, !new_cvs) | isCoVar old_id = (idvs, extendVarEnv cvs old_id (mkCoVarCo new_id))
+ | otherwise = (extendVarEnv idvs old_id (Var new_id), cvs)
{-
************************************************************************
--
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