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cmd/compile: clean up, document Node closure fields

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Requested during CL 23431.

Change-Id: I513ae42166b3a9fcfe51231ff55c163ab672e7d2
Reviewed-on: https://go-review.googlesource.com/23485
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Russ Cox 2016-05-27 00:56:19 -04:00
parent 93369001c7
commit 36a80c5941
7 changed files with 144 additions and 45 deletions
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49
src/cmd/compile/internal/gc/closure.go
View file

@ -66,8 +66,39 @@ func closurebody(body []*Node) *Node {
// unhook them.
// make the list of pointers for the closure call.
for _, v := range func_.Func.Cvars.Slice() {
v.Name.Param.Closure.Name.Param.Closure = v.Name.Param.Outer
v.Name.Param.Outerexpr = oldname(v.Sym)
// Unlink from v1; see comment in syntax.go type Param for these fields.
v1 := v.Name.Defn
v1.Name.Param.Innermost = v.Name.Param.Outer
// If the closure usage of v is not dense,
// we need to make it dense; now that we're out
// of the function in which v appeared,
// look up v.Sym in the enclosing function
// and keep it around for use in the compiled code.
//
// That is, suppose we just finished parsing the innermost
// closure f4 in this code:
//
// func f() {
// v := 1
// func() { // f2
// use(v)
// func() { // f3
// func() { // f4
// use(v)
// }()
// }()
// }()
// }
//
// At this point v.Outer is f2's v; there is no f3's v.
// To construct the closure f4 from within f3,
// we need to use f3's v and in this case we need to create f3's v.
// We are now in the context of f3, so calling oldname(v.Sym)
// obtains f3's v, creating it if necessary (as it is in the example).
//
// capturevars will decide whether to use v directly or &v.
v.Name.Param.Outer = oldname(v.Sym)
}
return func_
@ -75,7 +106,7 @@ func closurebody(body []*Node) *Node {
func typecheckclosure(func_ *Node, top int) {
for _, ln := range func_.Func.Cvars.Slice() {
n := ln.Name.Param.Closure
n := ln.Name.Defn
if !n.Name.Captured {
n.Name.Captured = true
if n.Name.Decldepth == 0 {
@ -215,8 +246,6 @@ func makeclosure(func_ *Node) *Node {
// We use value capturing for values <= 128 bytes that are never reassigned
// after capturing (effectively constant).
func capturevars(xfunc *Node) {
var outer *Node
lno := lineno
lineno = xfunc.Lineno
@ -239,14 +268,14 @@ func capturevars(xfunc *Node) {
// so that the outer frame also grabs them and knows they escape.
dowidth(v.Type)
outer = v.Name.Param.Outerexpr
v.Name.Param.Outerexpr = nil
outer := v.Name.Param.Outer
outermost := v.Name.Defn
// out parameters will be assigned to implicitly upon return.
if outer.Class != PPARAMOUT && !v.Name.Param.Closure.Addrtaken && !v.Name.Param.Closure.Assigned && v.Type.Width <= 128 {
if outer.Class != PPARAMOUT && !outermost.Addrtaken && !outermost.Assigned && v.Type.Width <= 128 {
v.Name.Byval = true
} else {
v.Name.Param.Closure.Addrtaken = true
outermost.Addrtaken = true
outer = Nod(OADDR, outer, nil)
}
@ -259,7 +288,7 @@ func capturevars(xfunc *Node) {
if v.Name.Byval {
how = "value"
}
Warnl(v.Lineno, "%v capturing by %s: %v (addr=%v assign=%v width=%d)", name, how, v.Sym, v.Name.Param.Closure.Addrtaken, v.Name.Param.Closure.Assigned, int32(v.Type.Width))
Warnl(v.Lineno, "%v capturing by %s: %v (addr=%v assign=%v width=%d)", name, how, v.Sym, outermost.Addrtaken, outermost.Assigned, int32(v.Type.Width))
}
outer = typecheck(outer, Erv)