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cmd/compile: rewrite f(g()) for multi-value g() during typecheck

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This CL moves order.go's copyRet logic for rewriting f(g()) into t1,
t2, ... = g(); f(t1, t2, ...) earlier into typecheck. This allows the
rest of the compiler to stop worrying about multi-value functions
appearing outside of OAS2FUNC nodes.

This changes compiler behavior in a few observable ways:

1. Typechecking error messages for builtin functions now use general
case error messages rather than unnecessarily differing ones.

2. Because f(g()) is rewritten before inlining, saved inline bodies
now see the rewritten form too. This could be addressed, but doesn't
seem worthwhile.

3. Most notably, this simplifies escape analysis and fixes a memory
corruption issue in esc.go. See #29197 for details.

Fixes #15992.
Fixes #29197.

Change-Id: I86a70668301efeec8fbd11fe2d242e359a3ad0af
Reviewed-on: https://go-review.googlesource.com/c/153841
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Matthew Dempsky 2018-12-12 11:15:37 -08:00
parent 9d40fadb1c
commit d96b7fbf98
13 changed files with 157 additions and 267 deletions
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60
src/cmd/compile/internal/gc/order.go
View file

@ -380,66 +380,12 @@ func (o *Order) init(n *Node) {
n.Ninit.Set(nil)
}
// Ismulticall reports whether the list l is f() for a multi-value function.
// Such an f() could appear as the lone argument to a multi-arg function.
func ismulticall(l Nodes) bool {
// one arg only
if l.Len() != 1 {
return false
}
n := l.First()
// must be call
switch n.Op {
default:
return false
case OCALLFUNC, OCALLMETH, OCALLINTER:
// call must return multiple values
return n.Left.Type.NumResults() > 1
}
}
// copyRet emits t1, t2, ... = n, where n is a function call,
// and then returns the list t1, t2, ....
func (o *Order) copyRet(n *Node) []*Node {
if !n.Type.IsFuncArgStruct() {
Fatalf("copyret %v %d", n.Type, n.Left.Type.NumResults())
}
slice := n.Type.Fields().Slice()
l1 := make([]*Node, len(slice))
l2 := make([]*Node, len(slice))
for i, t := range slice {
tmp := temp(t.Type)
l1[i] = tmp
l2[i] = tmp
}
as := nod(OAS2, nil, nil)
as.List.Set(l1)
as.Rlist.Set1(n)
as = typecheck(as, ctxStmt)
o.stmt(as)
return l2
}
// callArgs orders the list of call arguments *l.
func (o *Order) callArgs(l *Nodes) {
if ismulticall(*l) {
// return f() where f() is multiple values.
l.Set(o.copyRet(l.First()))
} else {
o.exprList(*l)
}
}
// call orders the call expression n.
// n.Op is OCALLMETH/OCALLFUNC/OCALLINTER or a builtin like OCOPY.
func (o *Order) call(n *Node) {
n.Left = o.expr(n.Left, nil)
n.Right = o.expr(n.Right, nil) // ODDDARG temp
o.callArgs(&n.List)
o.exprList(n.List)
if n.Op != OCALLFUNC {
return
@ -811,7 +757,7 @@ func (o *Order) stmt(n *Node) {
o.cleanTemp(t)
case ORETURN:
o.callArgs(&n.List)
o.exprList(n.List)
o.out = append(o.out, n)
// Special: clean case temporaries in each block entry.
@ -1174,7 +1120,7 @@ func (o *Order) expr(n, lhs *Node) *Node {
n.List.SetFirst(o.expr(n.List.First(), nil)) // order x
n.List.Second().Left = o.expr(n.List.Second().Left, nil) // order y
} else {
o.callArgs(&n.List)
o.exprList(n.List)
}
if lhs == nil || lhs.Op != ONAME && !samesafeexpr(lhs, n.List.First()) {