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cmd/compile: fix stenciling of conversions between interfaces

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Conversions need to allow nil through.
We do that using a CONVIFACE instead of a DOTTYPE.

Also reorganize how nonempty interfaces are handled.
For nonempty to empty, a simple CONVIFACE suffices.
For nonempty to nonempty, we need to call the runtime to get the
new itab. Use the entry from the dictionary to identify the
target interface type (if parameterized).

Fixes #47925

Change-Id: I4ffeed964318bb3e270b06f558e6ab9c5bfc7188
Reviewed-on: https://go-review.googlesource.com/c/go/+/344830
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Keith Randall 2021-08-24 15:41:11 -07:00
parent 4f0dedca71
commit 6a35e07512
6 changed files with 187 additions and 23 deletions
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64
src/cmd/compile/internal/noder/stencil.go
View file

@ -737,7 +737,7 @@ func (g *irgen) genericSubst(newsym *types.Sym, nameNode *ir.Name, shapes []*typ
return
}
c := n.(*ir.ConvExpr)
if c.X.Type().HasShape() {
if c.X.Type().HasShape() && !c.X.Type().IsInterface() {
ir.Dump("BAD FUNCTION", newf)
ir.Dump("BAD CONVERSION", c)
base.Fatalf("converting shape type to interface")
@ -1135,7 +1135,7 @@ func (subst *subster) node(n ir.Node) ir.Node {
x := x.(*ir.ConvExpr)
// Note: x's argument is still typed as a type parameter.
// m's argument now has an instantiated type.
if x.X.Type().HasTParam() {
if x.X.Type().HasTParam() || (x.X.Type().IsInterface() && x.Type().HasTParam()) {
m = convertUsingDictionary(subst.info, subst.info.dictParam, m.Pos(), m.(*ir.ConvExpr).X, x, m.Type(), x.X.Type())
}
case ir.ODOTTYPE, ir.ODOTTYPE2:
@ -1231,9 +1231,52 @@ func findDictType(info *instInfo, t *types.Type) int {
// CONVIFACE node or XDOT node (for a bound method call) that is causing the
// conversion.
func convertUsingDictionary(info *instInfo, dictParam *ir.Name, pos src.XPos, v ir.Node, gn ir.Node, dst, src *types.Type) ir.Node {
assert(src.HasTParam())
assert(src.HasTParam() || src.IsInterface() && gn.Type().HasTParam())
assert(dst.IsInterface())
if v.Type().IsInterface() {
// Converting from an interface. The shape-ness of the source doesn't really matter, as
// we'll be using the concrete type from the first interface word.
if dst.IsEmptyInterface() {
// Converting I2E. OCONVIFACE does that for us, and doesn't depend
// on what the empty interface was instantiated with. No dictionary entry needed.
v = ir.NewConvExpr(pos, ir.OCONVIFACE, dst, v)
v.SetTypecheck(1)
return v
}
gdst := gn.Type() // pre-stenciled destination type
if !gdst.HasTParam() {
// Regular OCONVIFACE works if the destination isn't parameterized.
v = ir.NewConvExpr(pos, ir.OCONVIFACE, dst, v)
v.SetTypecheck(1)
return v
}
// We get the destination interface type from the dictionary and the concrete
// type from the argument's itab. Call runtime.convI2I to get the new itab.
tmp := typecheck.Temp(v.Type())
as := ir.NewAssignStmt(pos, tmp, v)
as.SetTypecheck(1)
itab := ir.NewUnaryExpr(pos, ir.OITAB, tmp)
typed(types.Types[types.TUINTPTR].PtrTo(), itab)
idata := ir.NewUnaryExpr(pos, ir.OIDATA, tmp)
typed(types.Types[types.TUNSAFEPTR], idata)
fn := typecheck.LookupRuntime("convI2I")
fn.SetTypecheck(1)
types.CalcSize(fn.Type())
call := ir.NewCallExpr(pos, ir.OCALLFUNC, fn, nil)
typed(types.Types[types.TUINT8].PtrTo(), call)
ix := findDictType(info, gdst)
assert(ix >= 0)
inter := getDictionaryType(info, dictParam, pos, ix)
call.Args = []ir.Node{inter, itab}
i := ir.NewBinaryExpr(pos, ir.OEFACE, call, idata)
typed(dst, i)
i.PtrInit().Append(as)
return i
}
var rt ir.Node
if !dst.IsEmptyInterface() {
// We should have an itab entry in the dictionary. Using this itab
@ -1248,11 +1291,6 @@ func convertUsingDictionary(info *instInfo, dictParam *ir.Name, pos src.XPos, v
}
assert(ix >= 0)
rt = getDictionaryEntry(pos, dictParam, ix, info.dictLen)
} else if v.Type().IsInterface() {
ta := ir.NewTypeAssertExpr(pos, v, nil)
ta.SetType(dst)
ta.SetTypecheck(1)
return ta
} else {
ix := findDictType(info, src)
assert(ix >= 0)
@ -1261,19 +1299,13 @@ func convertUsingDictionary(info *instInfo, dictParam *ir.Name, pos src.XPos, v
}
// Figure out what the data field of the interface will be.
var data ir.Node
if v.Type().IsInterface() {
data = ir.NewUnaryExpr(pos, ir.OIDATA, v)
} else {
data = ir.NewConvExpr(pos, ir.OCONVIDATA, nil, v)
}
data := ir.NewConvExpr(pos, ir.OCONVIDATA, nil, v)
typed(types.Types[types.TUNSAFEPTR], data)
// Build an interface from the type and data parts.
var i ir.Node = ir.NewBinaryExpr(pos, ir.OEFACE, rt, data)
typed(dst, i)
return i
}
func (subst *subster) namelist(l []*ir.Name) []*ir.Name {
@ -1557,7 +1589,7 @@ func (g *irgen) finalizeSyms() {
default:
base.Fatalf("itab entry with unknown op %s", n.Op())
}
if srctype.IsInterface() {
if srctype.IsInterface() || dsttype.IsEmptyInterface() {
// No itab is wanted if src type is an interface. We
// will use a type assert instead.
d.off = objw.Uintptr(lsym, d.off, 0)