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mdempskymdempsky
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cmd/compile: rewrite f(g()) for multi-value g() during typecheck
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>
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13 files changed

+157
-267
lines changed

13 files changed

+157
-267
lines changed

‎src/cmd/compile/internal/gc/esc.go

Lines changed: 0 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1604,13 +1604,6 @@ func (e *EscState) esccall(call *Node, parent *Node) {
16041604
}
16051605

16061606
argList := call.List
1607-
if argList.Len() == 1 {
1608-
arg := argList.First()
1609-
if arg.Type.IsFuncArgStruct() { // f(g())
1610-
argList = e.nodeEscState(arg).Retval
1611-
}
1612-
}
1613-
16141607
args := argList.Slice()
16151608

16161609
if indirect {

‎src/cmd/compile/internal/gc/fmt.go

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1404,14 +1404,11 @@ func (n *Node) exprfmt(s fmt.State, prec int, mode fmtMode) {
14041404
}
14051405
mode.Fprintf(s, "sliceheader{%v,%v,%v}", n.Left, n.List.First(), n.List.Second())
14061406

1407-
case OCOPY:
1408-
mode.Fprintf(s, "%#v(%v, %v)", n.Op, n.Left, n.Right)
1409-
1410-
case OCOMPLEX:
1411-
if n.List.Len() == 1 {
1412-
mode.Fprintf(s, "%#v(%v)", n.Op, n.List.First())
1413-
} else {
1407+
case OCOMPLEX, OCOPY:
1408+
if n.Left != nil {
14141409
mode.Fprintf(s, "%#v(%v, %v)", n.Op, n.Left, n.Right)
1410+
} else {
1411+
mode.Fprintf(s, "%#v(%.v)", n.Op, n.List)
14151412
}
14161413

14171414
case OCONV,
@@ -1540,6 +1537,8 @@ func (n *Node) nodefmt(s fmt.State, flag FmtFlag, mode fmtMode) {
15401537
if flag&FmtLong != 0 && t != nil {
15411538
if t.Etype == TNIL {
15421539
fmt.Fprint(s, "nil")
1540+
} else if n.Op == ONAME && n.Name.AutoTemp() {
1541+
mode.Fprintf(s, "%v value", t)
15431542
} else {
15441543
mode.Fprintf(s, "%v (type %v)", n, t)
15451544
}

‎src/cmd/compile/internal/gc/iexport.go

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1387,7 +1387,8 @@ func (w *exportWriter) localIdent(s *types.Sym, v int32) {
13871387
return
13881388
}
13891389

1390-
if i := strings.LastIndex(name, "."); i >= 0 {
1390+
// TODO(mdempsky): Fix autotmp hack.
1391+
if i := strings.LastIndex(name, "."); i >= 0 && !strings.HasPrefix(name, ".autotmp_") {
13911392
Fatalf("unexpected dot in identifier: %v", name)
13921393
}
13931394

‎src/cmd/compile/internal/gc/init.go

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14,6 +14,9 @@ import (
1414
// the name, normally "pkg.init", is altered to "pkg.init.0".
1515
var renameinitgen int
1616

17+
// Dummy function for autotmps generated during typechecking.
18+
var dummyInitFn = nod(ODCLFUNC, nil, nil)
19+
1720
func renameinit() *types.Sym {
1821
s := lookupN("init.", renameinitgen)
1922
renameinitgen++
@@ -114,6 +117,12 @@ func fninit(n []*Node) {
114117
initsym := lookup("init")
115118
fn := dclfunc(initsym, nod(OTFUNC, nil, nil))
116119

120+
for _, dcl := range dummyInitFn.Func.Dcl {
121+
dcl.Name.Curfn = fn
122+
}
123+
fn.Func.Dcl = append(fn.Func.Dcl, dummyInitFn.Func.Dcl...)
124+
dummyInitFn = nil
125+
117126
// (3)
118127
a := nod(OIF, nil, nil)
119128
a.Left = nod(OGT, gatevar, nodintconst(1))

‎src/cmd/compile/internal/gc/inl.go

Lines changed: 2 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -589,24 +589,13 @@ func inlnode(n *Node, maxCost int32) *Node {
589589
}
590590

591591
inlnodelist(n.List, maxCost)
592-
switch n.Op {
593-
case OBLOCK:
592+
if n.Op == OBLOCK {
594593
for _, n2 := range n.List.Slice() {
595594
if n2.Op == OINLCALL {
596595
inlconv2stmt(n2)
597596
}
598597
}
599-
600-
case ORETURN, OCALLFUNC, OCALLMETH, OCALLINTER, OAPPEND, OCOMPLEX:
601-
// if we just replaced arg in f(arg()) or return arg with an inlined call
602-
// and arg returns multiple values, glue as list
603-
if n.List.Len() == 1 && n.List.First().Op == OINLCALL && n.List.First().Rlist.Len() > 1 {
604-
n.List.Set(inlconv2list(n.List.First()))
605-
break
606-
}
607-
fallthrough
608-
609-
default:
598+
} else {
610599
s := n.List.Slice()
611600
for i1, n1 := range s {
612601
if n1 != nil && n1.Op == OINLCALL {
@@ -1016,9 +1005,6 @@ func mkinlcall(n, fn *Node, maxCost int32) *Node {
10161005
// to pass as a slice.
10171006

10181007
numvals := n.List.Len()
1019-
if numvals == 1 && n.List.First().Type.IsFuncArgStruct() {
1020-
numvals = n.List.First().Type.NumFields()
1021-
}
10221008

10231009
x := as.List.Len()
10241010
for as.List.Len() < numvals {

‎src/cmd/compile/internal/gc/order.go

Lines changed: 3 additions & 57 deletions
Original file line numberDiff line numberDiff line change
@@ -380,66 +380,12 @@ func (o *Order) init(n *Node) {
380380
n.Ninit.Set(nil)
381381
}
382382

383-
// Ismulticall reports whether the list l is f() for a multi-value function.
384-
// Such an f() could appear as the lone argument to a multi-arg function.
385-
func ismulticall(l Nodes) bool {
386-
// one arg only
387-
if l.Len() != 1 {
388-
return false
389-
}
390-
n := l.First()
391-
392-
// must be call
393-
switch n.Op {
394-
default:
395-
return false
396-
case OCALLFUNC, OCALLMETH, OCALLINTER:
397-
// call must return multiple values
398-
return n.Left.Type.NumResults() > 1
399-
}
400-
}
401-
402-
// copyRet emits t1, t2, ... = n, where n is a function call,
403-
// and then returns the list t1, t2, ....
404-
func (o *Order) copyRet(n *Node) []*Node {
405-
if !n.Type.IsFuncArgStruct() {
406-
Fatalf("copyret %v %d", n.Type, n.Left.Type.NumResults())
407-
}
408-
409-
slice := n.Type.Fields().Slice()
410-
l1 := make([]*Node, len(slice))
411-
l2 := make([]*Node, len(slice))
412-
for i, t := range slice {
413-
tmp := temp(t.Type)
414-
l1[i] = tmp
415-
l2[i] = tmp
416-
}
417-
418-
as := nod(OAS2, nil, nil)
419-
as.List.Set(l1)
420-
as.Rlist.Set1(n)
421-
as = typecheck(as, ctxStmt)
422-
o.stmt(as)
423-
424-
return l2
425-
}
426-
427-
// callArgs orders the list of call arguments *l.
428-
func (o *Order) callArgs(l *Nodes) {
429-
if ismulticall(*l) {
430-
// return f() where f() is multiple values.
431-
l.Set(o.copyRet(l.First()))
432-
} else {
433-
o.exprList(*l)
434-
}
435-
}
436-
437383
// call orders the call expression n.
438384
// n.Op is OCALLMETH/OCALLFUNC/OCALLINTER or a builtin like OCOPY.
439385
func (o *Order) call(n *Node) {
440386
n.Left = o.expr(n.Left, nil)
441387
n.Right = o.expr(n.Right, nil) // ODDDARG temp
442-
o.callArgs(&n.List)
388+
o.exprList(n.List)
443389

444390
if n.Op != OCALLFUNC {
445391
return
@@ -811,7 +757,7 @@ func (o *Order) stmt(n *Node) {
811757
o.cleanTemp(t)
812758

813759
case ORETURN:
814-
o.callArgs(&n.List)
760+
o.exprList(n.List)
815761
o.out = append(o.out, n)
816762

817763
// Special: clean case temporaries in each block entry.
@@ -1174,7 +1120,7 @@ func (o *Order) expr(n, lhs *Node) *Node {
11741120
n.List.SetFirst(o.expr(n.List.First(), nil)) // order x
11751121
n.List.Second().Left = o.expr(n.List.Second().Left, nil) // order y
11761122
} else {
1177-
o.callArgs(&n.List)
1123+
o.exprList(n.List)
11781124
}
11791125

11801126
if lhs == nil || lhs.Op != ONAME && !samesafeexpr(lhs, n.List.First()) {

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