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[dev.regabi] cmd/compile: cleanup OAS2FUNC ordering

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Currently, to ensure OAS2FUNC results are assigned in the correct
order, they're always assigned to temporary variables. However, these
temporary variables are typed based on the destination type, which may
require an interface conversion. This means walk may have to then
introduce a second set of temporaries to ensure result parameters are
all copied out of the results area, before it emits calls to runtime
conversion functions.

That's just silly. Instead, this CL changes order to allocate the
result temporaries with the same type as the function returns in the
first place, and then assign them one at a time to their destinations,
with conversions as needed.

While here, also fix an order-of-evaluation issue with has-ok
assignments that I almost added to multi-value function call
assignments, and add tests for each.

Change-Id: I9f4e962425fe3c5e3305adbbfeae2c7f253ec365
Reviewed-on: https://go-review.googlesource.com/c/go/+/284220
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 2021-01-16 03:27:17 -08:00
parent a956a0e909
commit 6de9423445
3 changed files with 57 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
src/cmd/compile/internal/walk/assign.go
View File

@ -268,7 +268,7 @@ func ascompatet(nl ir.Nodes, nr *types.Type) []ir.Node {
base.Fatalf("ascompatet: assignment count mismatch: %d = %d", len(nl), nr.NumFields())
}
var nn, mm ir.Nodes
var nn ir.Nodes
for i, l := range nl {
if ir.IsBlank(l) {
continue
@ -278,11 +278,7 @@ func ascompatet(nl ir.Nodes, nr *types.Type) []ir.Node {
// Any assignment to an lvalue that might cause a function call must be
// deferred until all the returned values have been read.
if fncall(l, r.Type) {
tmp := ir.Node(typecheck.Temp(r.Type))
tmp = typecheck.Expr(tmp)
a := convas(ir.NewAssignStmt(base.Pos, l, tmp), &mm)
mm.Append(a)
l = tmp
base.FatalfAt(l.Pos(), "assigning %v to %+v", r.Type, l)
}
res := ir.NewResultExpr(base.Pos, nil, types.BADWIDTH)
@ -299,7 +295,7 @@ func ascompatet(nl ir.Nodes, nr *types.Type) []ir.Node {
nn.Append(a)
}
return append(nn, mm...)
return nn
}
// check assign expression list to

83
src/cmd/compile/internal/walk/order.go
View File

@ -555,10 +555,6 @@ func (o *orderState) mapAssign(n ir.Node) {
n.Y = o.safeMapRHS(n.Y)
}
o.out = append(o.out, n)
case ir.OAS2, ir.OAS2DOTTYPE, ir.OAS2MAPR, ir.OAS2FUNC:
n := n.(*ir.AssignListStmt)
o.out = append(o.out, n)
}
}
@ -637,7 +633,7 @@ func (o *orderState) stmt(n ir.Node) {
t := o.markTemp()
o.exprList(n.Lhs)
o.exprList(n.Rhs)
o.mapAssign(n)
o.out = append(o.out, n)
o.cleanTemp(t)
// Special: avoid copy of func call n.Right
@ -647,7 +643,7 @@ func (o *orderState) stmt(n ir.Node) {
o.exprList(n.Lhs)
o.init(n.Rhs[0])
o.call(n.Rhs[0])
o.as2(n)
o.as2func(n)
o.cleanTemp(t)
// Special: use temporary variables to hold result,
@ -679,7 +675,7 @@ func (o *orderState) stmt(n ir.Node) {
base.Fatalf("order.stmt: %v", r.Op())
}
o.okAs2(n)
o.as2ok(n)
o.cleanTemp(t)
// Special: does not save n onto out.
@ -1390,57 +1386,54 @@ func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
// No return - type-assertions above. Each case must return for itself.
}
// as2 orders OAS2XXXX nodes. It creates temporaries to ensure left-to-right assignment.
// The caller should order the right-hand side of the assignment before calling order.as2.
// as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
// The caller should order the right-hand side of the assignment before calling order.as2func.
// It rewrites,
// a, b, a = ...
// a, b, a = ...
// as
// tmp1, tmp2, tmp3 = ...
// a, b, a = tmp1, tmp2, tmp3
// a, b, a = tmp1, tmp2, tmp3
// This is necessary to ensure left to right assignment order.
func (o *orderState) as2(n *ir.AssignListStmt) {
tmplist := []ir.Node{}
left := []ir.Node{}
for ni, l := range n.Lhs {
if !ir.IsBlank(l) {
tmp := o.newTemp(l.Type(), l.Type().HasPointers())
n.Lhs[ni] = tmp
tmplist = append(tmplist, tmp)
left = append(left, l)
func (o *orderState) as2func(n *ir.AssignListStmt) {
results := n.Rhs[0].Type()
as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
for i, nl := range n.Lhs {
if !ir.IsBlank(nl) {
typ := results.Field(i).Type
tmp := o.newTemp(typ, typ.HasPointers())
n.Lhs[i] = tmp
as.Lhs = append(as.Lhs, nl)
as.Rhs = append(as.Rhs, tmp)
}
}
o.out = append(o.out, n)
as := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
as.Lhs = left
as.Rhs = tmplist
o.stmt(typecheck.Stmt(as))
}
// okAs2 orders OAS2XXX with ok.
// Just like as2, this also adds temporaries to ensure left-to-right assignment.
func (o *orderState) okAs2(n *ir.AssignListStmt) {
var tmp1, tmp2 ir.Node
if !ir.IsBlank(n.Lhs[0]) {
typ := n.Rhs[0].Type()
tmp1 = o.newTemp(typ, typ.HasPointers())
// as2ok orders OAS2XXX with ok.
// Just like as2func, this also adds temporaries to ensure left-to-right assignment.
func (o *orderState) as2ok(n *ir.AssignListStmt) {
as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
do := func(i int, typ *types.Type) {
if nl := n.Lhs[i]; !ir.IsBlank(nl) {
var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
n.Lhs[i] = tmp
as.Lhs = append(as.Lhs, nl)
if i == 1 {
// The "ok" result is an untyped boolean according to the Go
// spec. We need to explicitly convert it to the LHS type in
// case the latter is a defined boolean type (#8475).
tmp = typecheck.Conv(tmp, nl.Type())
}
as.Rhs = append(as.Rhs, tmp)
}
}
if !ir.IsBlank(n.Lhs[1]) {
tmp2 = o.newTemp(types.Types[types.TBOOL], false)
}
do(0, n.Rhs[0].Type())
do(1, types.Types[types.TBOOL])
o.out = append(o.out, n)
if tmp1 != nil {
r := ir.NewAssignStmt(base.Pos, n.Lhs[0], tmp1)
o.mapAssign(typecheck.Stmt(r))
n.Lhs[0] = tmp1
}
if tmp2 != nil {
r := ir.NewAssignStmt(base.Pos, n.Lhs[1], typecheck.Conv(tmp2, n.Lhs[1].Type()))
o.mapAssign(typecheck.Stmt(r))
n.Lhs[1] = tmp2
}
o.stmt(typecheck.Stmt(as))
}

16
test/reorder.go
View File

@ -20,6 +20,8 @@ func main() {
p7()
p8()
p9()
p10()
p11()
}
var gx []int
@ -149,3 +151,17 @@ func checkOAS2XXX(x bool, s string) {
panic("failed")
}
}
//go:noinline
func fp() (*int, int) { return nil, 42 }
func p10() {
p := new(int)
p, *p = fp()
}
func p11() {
var i interface{}
p := new(bool)
p, *p = i.(*bool)
}