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go/types, types2: simplify locking in Named.resolveUnderlying

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Avoid calling Named.resolveUnderlying in the first place (there
is only one caller) if Named.underlying exists already.

In Named.resolveUnderlying remove initial atomic check because
of the check in Named.Underlying. Also, remove a 2nd atomic
check after acquiring the lock as it likely won't help much.

Change-Id: Ife87218fa2549d0903a10218f4dd7a70f85d6c7c
Reviewed-on: https://go-review.googlesource.com/c/go/+/713521
Auto-Submit: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
This commit is contained in:
Robert Griesemer 2025-10-21 15:04:46 -07:00 • committed by Gopher Robot
parent 5a42af7f6c
commit d09a8c8ef4
2 changed files with 16 additions and 24 deletions
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20
src/cmd/compile/internal/types2/named.go
View file

@ -562,7 +562,10 @@ func (n *Named) Underlying() Type {
}
}
n.resolveUnderlying()
if !n.stateHas(underlying) {
n.resolveUnderlying()
}
return n.underlying
}
@ -588,11 +591,6 @@ func (t *Named) String() string { return TypeString(t, nil) }
func (n *Named) resolveUnderlying() {
assert(n.stateHas(resolved))
// optimization for likely case
if n.stateHas(underlying) {
return
}
var seen map[*Named]int // allocated lazily
var u Type
for rhs := Type(n); u == nil; {
@ -618,12 +616,7 @@ func (n *Named) resolveUnderlying() {
break
}
// acquire the lock without checking; performance is probably fine
t.resolve()
t.mu.Lock()
defer t.mu.Unlock()
// t.underlying might have been set while we were locking
// avoid acquiring the lock if we can
if t.stateHas(underlying) {
u = t.underlying
break
@ -634,6 +627,9 @@ func (n *Named) resolveUnderlying() {
}
seen[t] = len(seen)
t.resolve()
t.mu.Lock()
defer t.mu.Unlock()
assert(t.fromRHS != nil || t.allowNilRHS)
rhs = t.fromRHS

20
src/go/types/named.go
View file

@ -565,7 +565,10 @@ func (n *Named) Underlying() Type {
}
}
n.resolveUnderlying()
if !n.stateHas(underlying) {
n.resolveUnderlying()
}
return n.underlying
}
@ -591,11 +594,6 @@ func (t *Named) String() string { return TypeString(t, nil) }
func (n *Named) resolveUnderlying() {
assert(n.stateHas(resolved))
// optimization for likely case
if n.stateHas(underlying) {
return
}
var seen map[*Named]int // allocated lazily
var u Type
for rhs := Type(n); u == nil; {
@ -621,12 +619,7 @@ func (n *Named) resolveUnderlying() {
break
}
// acquire the lock without checking; performance is probably fine
t.resolve()
t.mu.Lock()
defer t.mu.Unlock()
// t.underlying might have been set while we were locking
// avoid acquiring the lock if we can
if t.stateHas(underlying) {
u = t.underlying
break
@ -637,6 +630,9 @@ func (n *Named) resolveUnderlying() {
}
seen[t] = len(seen)
t.resolve()
t.mu.Lock()
defer t.mu.Unlock()
assert(t.fromRHS != nil || t.allowNilRHS)
rhs = t.fromRHS