cmd/compile: encapsulate reads of gc.Type.Funarg

Changes generated with eg and then manually
checked and in some cases simplified.

Passes toolstash -cmp.

Change-Id: I2119f37f003368ce1884d2863b406d6ffbfe38c7
Reviewed-on: https://go-review.googlesource.com/21563Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -263,7 +263,7 @@ func dowidth(t *Type) {
 		}
 
 	case TSTRUCT:
-		if t.Funarg {
+		if t.IsFuncArgStruct() {
 			Fatalf("dowidth fn struct %v", t)
 		}
 		w = widstruct(t, t, 0, 1)
@@ -335,7 +335,7 @@ func checkwidth(t *Type) {
 
 	// function arg structs should not be checked
 	// outside of the enclosing function.
-	if t.Funarg {
+	if t.IsFuncArgStruct() {
 		Fatalf("checkwidth %v", t)
 	}
 

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

@@ -742,7 +742,7 @@ func basetypeName(t *Type) string {
 }
 
 func (p *exporter) paramList(params *Type, numbered bool) {
-	if !params.IsStruct() || !params.Funarg {
+	if !params.IsFuncArgStruct() {
 		Fatalf("exporter: parameter list expected")
 	}
 

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

@@ -1435,7 +1435,7 @@ func esccall(e *EscState, n *Node, up *Node) {
 	ll := n.List
 	if n.List.Len() == 1 {
 		a := n.List.First()
-		if a.Type.IsStruct() && a.Type.Funarg { // f(g()).
+		if a.Type.IsFuncArgStruct() { // f(g())
 			ll = e.nodeEscState(a).Escretval
 		}
 	}

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

@@ -592,7 +592,7 @@ func dumpasmhdr() {
 
 		case OTYPE:
 			t := n.Type
-			if !t.IsStruct() || t.Map != nil || t.Funarg {
+			if !t.IsStruct() || t.Map != nil || t.IsFuncArgStruct() {
 				break
 			}
 			fmt.Fprintf(b, "#define %s__size %d\n", t.Sym.Name, int(t.Width))

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

@@ -690,7 +690,7 @@ func typefmt(t *Type, flag FmtFlag) string {
 		}
 
 		var buf bytes.Buffer
-		if t.Funarg {
+		if t.IsFuncArgStruct() {
 			buf.WriteString("(")
 			var flag1 FmtFlag
 			if fmtmode == FTypeId || fmtmode == FErr { // no argument names on function signature, and no "noescape"/"nosplit" tags

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

@@ -541,7 +541,7 @@ func nodarg(t interface{}, fp int) *Node {
 	switch t := t.(type) {
 	case *Type:
 		// entire argument struct, not just one arg
-		if !t.IsStruct() || !t.Funarg {
+		if !t.IsFuncArgStruct() {
 			Fatalf("nodarg: bad type %v", t)
 		}
 		n = Nod(ONAME, nil, nil)

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

@@ -324,7 +324,7 @@ func ismulticall(l Nodes) bool {
 // Copyret emits t1, t2, ... = n, where n is a function call,
 // and then returns the list t1, t2, ....
 func copyret(n *Node, order *Order) []*Node {
-	if !n.Type.IsStruct() || !n.Type.Funarg {
+	if !n.Type.IsFuncArgStruct() {
 		Fatalf("copyret %v %d", n.Type, n.Left.Type.Results().NumFields())
 	}
 

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

@@ -127,7 +127,7 @@ type Type struct {
 	Chan        ChanDir
 	Trecur      uint8 // to detect loops
 	Printed     bool
-	Funarg      bool // on TSTRUCT and TFIELD
+	Funarg      bool // TSTRUCT only: whether this struct represents function parameters
 	Local       bool // created in this file
 	Deferwidth  bool
 	Broke       bool // broken type definition.
@@ -566,6 +566,11 @@ func (t *Type) SetNname(n *Node) {
 	t.nname = n
 }
 
+// IsFuncArgStruct reports whether t is a struct representing function parameters.
+func (t *Type) IsFuncArgStruct() bool {
+	return t.Etype == TSTRUCT && t.Funarg
+}
+
 func (t *Type) Methods() *Fields {
 	// TODO(mdempsky): Validate t?
 	return &t.methods

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

@@ -1607,7 +1607,7 @@ OpSwitch:
 
 		// Unpack multiple-return result before type-checking.
 		var funarg *Type
-		if t.IsStruct() && t.Funarg {
+		if t.IsFuncArgStruct() {
 			funarg = t
 			t = t.Field(0).Type
 		}
@@ -2159,7 +2159,7 @@ OpSwitch:
 	}
 
 	t := n.Type
-	if t != nil && !t.Funarg && n.Op != OTYPE {
+	if t != nil && !t.IsFuncArgStruct() && n.Op != OTYPE {
 		switch t.Etype {
 		case TFUNC, // might have TANY; wait until its called
 			TANY,
@@ -2611,7 +2611,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *Type, nl Nodes, desc
 	if nl.Len() == 1 {
 		n = nl.First()
 		if n.Type != nil {
-			if n.Type.IsStruct() && n.Type.Funarg {
+			if n.Type.IsFuncArgStruct() {
 				if !hasddd(tstruct) {
 					n1 := tstruct.NumFields()
 					n2 := n.Type.NumFields()
@@ -3359,7 +3359,7 @@ func typecheckas2(n *Node) {
 		}
 		switch r.Op {
 		case OCALLMETH, OCALLINTER, OCALLFUNC:
-			if !r.Type.IsStruct() || !r.Type.Funarg {
+			if !r.Type.IsFuncArgStruct() {
 				break
 			}
 			cr = r.Type.NumFields()

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

@@ -1783,7 +1783,7 @@ func ascompatte(op Op, call *Node, isddd bool, nl *Type, lr []*Node, fp int, ini
 	var nn []*Node
 
 	// f(g()) where g has multiple return values
-	if r != nil && len(lr) <= 1 && r.Type.IsStruct() && r.Type.Funarg {
+	if r != nil && len(lr) <= 1 && r.Type.IsFuncArgStruct() {
 		// optimization - can do block copy
 		if eqtypenoname(r.Type, nl) {
 			arg := nodarg(nl, fp)