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cmd/compile/internal/ir: add NewZero
This constructs a zero value of any type, which helps address some corner case scenarios. It should also eventually handle the predeclared "zero" value, at least as currently implemented in go.dev/cl/520336. For #61372. Change-Id: I3a86a94fd8fa388c9c6bf281da8aa532b3da00fc Reviewed-on: https://go-review.googlesource.com/c/go/+/527696 Auto-Submit: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Than McIntosh <thanm@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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@ -34,6 +34,36 @@ func NewUintptr(pos src.XPos, v int64) Node {
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return NewBasicLit(pos, types.Types[types.TUINTPTR], constant.MakeInt64(v))
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}
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// NewZero returns a zero value of the given type.
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func NewZero(pos src.XPos, typ *types.Type) Node {
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switch {
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case typ.HasNil():
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return NewNilExpr(pos, typ)
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case typ.IsInteger():
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return NewBasicLit(pos, typ, intZero)
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case typ.IsFloat():
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return NewBasicLit(pos, typ, floatZero)
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case typ.IsComplex():
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return NewBasicLit(pos, typ, complexZero)
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case typ.IsBoolean():
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return NewBasicLit(pos, typ, constant.MakeBool(false))
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case typ.IsString():
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return NewBasicLit(pos, typ, constant.MakeString(""))
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case typ.IsArray() || typ.IsStruct():
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// TODO(mdempsky): Return a typechecked expression instead.
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return NewCompLitExpr(pos, OCOMPLIT, typ, nil)
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}
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base.FatalfAt(pos, "unexpected type: %v", typ)
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panic("unreachable")
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}
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var (
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intZero = constant.MakeInt64(0)
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floatZero = constant.ToFloat(intZero)
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complexZero = constant.ToComplex(intZero)
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)
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// NewOne returns an OLITERAL representing 1 with the given type.
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func NewOne(pos src.XPos, typ *types.Type) Node {
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var val constant.Value
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@ -58,7 +58,7 @@ const (
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exprSizeof
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exprAlignof
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exprOffsetof
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exprNil
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exprZero
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exprFuncInst
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exprRecv
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exprReshape
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@ -59,10 +59,6 @@ func FixValue(typ *types.Type, val constant.Value) constant.Value {
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return val
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}
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func Nil(pos src.XPos, typ *types.Type) ir.Node {
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return ir.NewNilExpr(pos, typ)
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}
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// Expressions
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func Addr(pos src.XPos, x ir.Node) *ir.AddrExpr {
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@ -1340,16 +1340,9 @@ func (r *reader) syntheticArgs(pos src.XPos) (recvs, params ir.Nodes) {
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// For anonymous and blank parameters, we don't have an *ir.Name
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// to use as the argument. However, since we know the shaped
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// function won't use the value either, we can just pass the
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// zero value. (Also unfortunately, we don't have an easy
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// zero-value IR node; so we use a default-initialized temporary
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// variable.)
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// zero value.
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if arg == nil {
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tmp := typecheck.TempAt(pos, r.curfn, param.Type)
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r.curfn.Body.Append(
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typecheck.Stmt(ir.NewDecl(pos, ir.ODCL, tmp)),
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typecheck.Stmt(ir.NewAssignStmt(pos, tmp, nil)),
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)
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arg = tmp
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arg = ir.NewZero(pos, param.Type)
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}
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out.Append(arg)
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@ -2177,10 +2170,10 @@ func (r *reader) expr() (res ir.Node) {
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val := FixValue(typ, r.Value())
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return ir.NewBasicLit(pos, typ, val)
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case exprNil:
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case exprZero:
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pos := r.pos()
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typ := r.typ()
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return Nil(pos, typ)
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return ir.NewZero(pos, typ)
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case exprCompLit:
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return r.compLit()
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@ -1752,7 +1752,7 @@ func (w *writer) expr(expr syntax.Expr) {
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}
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if _, isNil := obj.(*types2.Nil); isNil {
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w.Code(exprNil)
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w.Code(exprZero)
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w.pos(expr)
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w.typ(tv.Type)
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return
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