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[dev.regabi] cmd/compile: simplify CaptureVars

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CaptureVars is responsible for deciding whether free variables should
be captured by value or by reference, but currently it also makes up
for some of the short-comings of the frontend symbol resolution /
type-checking algorithms. These are really separate responsibilities,
so move the latter into type-checking where it fits better.

Passes toolstash -cmp.

Change-Id: Iffbd53e83846a9ca9dfb54b597450b8543252850
Reviewed-on: https://go-review.googlesource.com/c/go/+/281534
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2021-01-04 18:28:55 -08:00
parent c28ca67a96
commit eb626409d1
1 changed files with 21 additions and 28 deletions
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49
src/cmd/compile/internal/typecheck/func.go
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@ -106,26 +106,7 @@ func PartialCallType(n *ir.SelectorExpr) *types.Type {
// We use value capturing for values <= 128 bytes that are never reassigned
// after capturing (effectively constant).
func CaptureVars(fn *ir.Func) {
lno := base.Pos
base.Pos = fn.Pos()
cvars := fn.ClosureVars
out := cvars[:0]
for _, v := range cvars {
if v.Type() == nil {
// If v.Type is nil, it means v looked like it
// was going to be used in the closure, but
// isn't. This happens in struct literals like
// s{f: x} where we can't distinguish whether
// f is a field identifier or expression until
// resolving s.
continue
}
out = append(out, v)
// type check closed variables outside the closure,
// so that the outer frame also grabs them and knows they escape.
Expr(v.Outer)
for _, v := range fn.ClosureVars {
outermost := v.Defn.(*ir.Name)
// out parameters will be assigned to implicitly upon return.
@ -136,20 +117,13 @@ func CaptureVars(fn *ir.Func) {
}
if base.Flag.LowerM > 1 {
var name *types.Sym
if v.Curfn != nil && v.Curfn.Nname != nil {
name = v.Curfn.Sym()
}
how := "ref"
if v.Byval() {
how = "value"
}
base.WarnfAt(v.Pos(), "%v capturing by %s: %v (addr=%v assign=%v width=%d)", name, how, v.Sym(), outermost.Addrtaken(), outermost.Assigned(), v.Type().Size())
base.WarnfAt(v.Pos(), "%v capturing by %s: %v (addr=%v assign=%v width=%d)", v.Curfn, how, v, outermost.Addrtaken(), outermost.Assigned(), v.Type().Size())
}
}
fn.ClosureVars = out
base.Pos = lno
}
// Lazy typechecking of imported bodies. For local functions, caninl will set ->typecheck
@ -396,6 +370,25 @@ func tcClosure(clo *ir.ClosureExpr, top int) {
ir.CurFunc = oldfn
}
out := 0
for _, v := range fn.ClosureVars {
if v.Type() == nil {
// If v.Type is nil, it means v looked like it was going to be
// used in the closure, but isn't. This happens in struct
// literals like s{f: x} where we can't distinguish whether f is
// a field identifier or expression until resolving s.
continue
}
// type check closed variables outside the closure, so that the
// outer frame also captures them.
Expr(v.Outer)
fn.ClosureVars[out] = v
out++
}
fn.ClosureVars = fn.ClosureVars[:out]
Target.Decls = append(Target.Decls, fn)
}