cmd/gc: improve escape analysis for &T{...}
Currently all PTRLIT element initializers escape. There is no reason for that.
This change links STRUCTLIT to PTRLIT; STRUCTLIT element initializers are
already linked to the STRUCTLIT. As the result, PTRLIT element initializers
escape when PTRLIT itself escapes.
Change-Id: I89ecd8677cbf81addcfd469cd2fd461c0e9bf7dd
Reviewed-on: https://go-review.googlesource.com/3031
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/cmd/gc/esc.c b/src/cmd/gc/esc.c
index 7c7095c..2fdbd99 100644
--- a/src/cmd/gc/esc.c
+++ b/src/cmd/gc/esc.c
@@ -615,15 +615,15 @@
for(ll=n->list; ll; ll=ll->next)
escassign(e, n, ll->n->right);
break;
-
+
case OPTRLIT:
n->esc = EscNone; // until proven otherwise
e->noesc = list(e->noesc, n);
n->escloopdepth = e->loopdepth;
- // Contents make it to memory, lose track.
- escassign(e, &e->theSink, n->left);
+ // Link OSTRUCTLIT to OPTRLIT; if OPTRLIT escapes, OSTRUCTLIT elements do too.
+ escassign(e, n, n->left);
break;
-
+
case OCALLPART:
n->esc = EscNone; // until proven otherwise
e->noesc = list(e->noesc, n);
@@ -730,6 +730,7 @@
case OCONVNOP:
case OMAPLIT:
case OSTRUCTLIT:
+ case OPTRLIT:
case OCALLPART:
break;
diff --git a/test/escape2.go b/test/escape2.go
index 6a46ce8..357ce4a 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1492,3 +1492,30 @@
x = &x // ERROR "&x escapes to heap"
return
}
+
+var sink interface{}
+
+type Lit struct {
+ p *int
+}
+
+func ptrlitNoescape() {
+ // Both literal and element do not escape.
+ i := 0
+ x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i does not escape"
+ _ = x
+}
+
+func ptrlitNoEscape2() {
+ // Literal does not escape, but element does.
+ i := 0 // ERROR "moved to heap: i"
+ x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i escapes to heap"
+ sink = *x
+}
+
+func ptrlitEscape() {
+ // Both literal and element escape.
+ i := 0 // ERROR "moved to heap: i"
+ x := &Lit{&i} // ERROR "&Lit literal escapes to heap" "&i escapes to heap"
+ sink = x
+}
diff --git a/test/escape2n.go b/test/escape2n.go
index 002a78e..3e9bb70 100644
--- a/test/escape2n.go
+++ b/test/escape2n.go
@@ -1492,3 +1492,30 @@
x = &x // ERROR "&x escapes to heap"
return
}
+
+var sink interface{}
+
+type Lit struct {
+ p *int
+}
+
+func ptrlitNoescape() {
+ // Both literal and element do not escape.
+ i := 0
+ x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i does not escape"
+ _ = x
+}
+
+func ptrlitNoEscape2() {
+ // Literal does not escape, but element does.
+ i := 0 // ERROR "moved to heap: i"
+ x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i escapes to heap"
+ sink = *x
+}
+
+func ptrlitEscape() {
+ // Both literal and element escape.
+ i := 0 // ERROR "moved to heap: i"
+ x := &Lit{&i} // ERROR "&Lit literal escapes to heap" "&i escapes to heap"
+ sink = x
+}
