cmd/compile: copy captured dictionary var to local var

When starting a closure that needs a dictionary, copy the closure
variable to a local variable. This lets child closures capture that
dictionary variable correctly.

This is a better fix for #47684, which does not cause problems
like #47723.

Fixes #47723
Update #47684

Change-Id: Ib5d9ffc68a5142e28daa7d0d75683e7a35508540
Reviewed-on: https://go-review.googlesource.com/c/go/+/343871
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Keith Randall 2021-08-20 10:19:28 -07:00
parent aeec6dbfe0
commit 8486ced8b0
3 changed files with 38 additions and 5 deletions

View file

@ -404,9 +404,7 @@ func CaptureName(pos src.XPos, fn *Func, n *Name) *Name {
if n.Op() != ONAME || n.Curfn == nil {
return n // okay to use directly
}
if n.IsClosureVar() && n.Sym().Name != ".dict" {
// Note: capturing dictionary closure variables is ok. This makes
// sure the generated code is correctly optimized.
if n.IsClosureVar() {
base.FatalfAt(pos, "misuse of CaptureName on closure variable: %v", n)
}

View file

@ -1087,13 +1087,25 @@ func (subst *subster) node(n ir.Node) ir.Node {
ir.FinishCaptureNames(oldfn.Pos(), saveNewf, newfn)
newfn.ClosureVars = append(newfn.ClosureVars, subst.namelist(oldfn.ClosureVars)...)
// Copy that closure variable to a local one.
// Note: this allows the dictionary to be captured by child closures.
// See issue 47723.
ldict := ir.NewNameAt(x.Pos(), subst.info.gf.Sym().Pkg.Lookup(".dict"))
typed(types.Types[types.TUINTPTR], ldict)
ldict.Class = ir.PAUTO
ldict.Curfn = newfn
newfn.Dcl = append(newfn.Dcl, ldict)
as := ir.NewAssignStmt(x.Pos(), ldict, cdict)
as.SetTypecheck(1)
newfn.Body.Append(as)
// Create inst info for the instantiated closure. The dict
// param is the closure variable for the dictionary of the
// outer function. Since the dictionary is shared, use the
// same entries for startSubDict, dictLen, dictEntryMap.
cinfo := &instInfo{
fun: newfn,
dictParam: cdict,
dictParam: ldict,
gf: subst.info.gf,
gfInfo: subst.info.gfInfo,
startSubDict: subst.info.startSubDict,
@ -1110,7 +1122,7 @@ func (subst *subster) node(n ir.Node) ir.Node {
outerinfo := subst.info
subst.info = cinfo
// Make sure type of closure function is set before doing body.
newfn.Body = subst.list(oldfn.Body)
newfn.Body.Append(subst.list(oldfn.Body)...)
subst.info = outerinfo
subst.newf = saveNewf
ir.CurFunc = saveNewf

View file

@ -0,0 +1,23 @@
// run -gcflags=-G=3
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
func f[_ any]() int {
var a [1]int
_ = func() int {
return func() int {
return 0
}()
}()
return a[func() int {
return 0
}()]
}
func main() {
f[int]()
}