cmd/compile: clean up various bits of code

* replace a copy of IsMethod with a call of it.
* a few more switches where they simplify the code.
* prefer composite literals over "n := new(...); n.x = y; ...".
* use defers to get rid of three goto labels.
* rewrite updateHasCall into two funcs to remove gotos.

Passes toolstash-check on std cmd.

Change-Id: Icb5442a89a87319ef4b640bbc5faebf41b193ef1
Reviewed-on: https://go-review.googlesource.com/72070
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -1373,7 +1373,8 @@ func defaultlitreuse(n *Node, t *types.Type, reuse canReuseNode) *Node {
 			return convlit(n, t)
 		}
 
-		if n.Val().Ctype() == CTNIL {
+		switch n.Val().Ctype() {
+		case CTNIL:
 			lineno = lno
 			if !n.Diag() {
 				yyerror("use of untyped nil")
@@ -1381,16 +1382,12 @@ func defaultlitreuse(n *Node, t *types.Type, reuse canReuseNode) *Node {
 			}
 
 			n.Type = nil
-			break
-		}
-
-		if n.Val().Ctype() == CTSTR {
+		case CTSTR:
 			t1 := types.Types[TSTRING]
 			n = convlit1(n, t1, false, reuse)
-			break
-		}
-
+		default:
 			yyerror("defaultlit: unknown literal: %v", n)
+		}
 
 	case CTxxx:
 		Fatalf("defaultlit: idealkind is CTxxx: %+v", n)

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

@@ -205,9 +205,7 @@ const (
 // allowed level when a loop is encountered. Using -2 suffices to
 // pass all the tests we have written so far, which we assume matches
 // the level of complexity we want the escape analysis code to handle.
-const (
-	MinLevel = -2
-)
+const MinLevel = -2
 
 // A Level encodes the reference state and context applied to
 // (stack, heap) allocated memory.

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

@@ -83,7 +83,7 @@ func autoexport(n *Node, ctxt Class) {
 	if (ctxt != PEXTERN && ctxt != PFUNC) || dclcontext != PEXTERN {
 		return
 	}
-	if n.Type != nil && n.Type.IsKind(TFUNC) && n.Type.Recv() != nil { // method
+	if n.Type != nil && n.Type.IsKind(TFUNC) && n.IsMethod() {
 		return
 	}
 

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

@@ -70,13 +70,13 @@ func newProgs(fn *Node, worker int) *Progs {
 }
 
 func (pp *Progs) NewProg() *obj.Prog {
+	var p *obj.Prog
 	if pp.cacheidx < len(pp.progcache) {
-		p := &pp.progcache[pp.cacheidx]
-		p.Ctxt = Ctxt
+		p = &pp.progcache[pp.cacheidx]
 		pp.cacheidx++
-		return p
+	} else {
+		p = new(obj.Prog)
 	}
-	p := new(obj.Prog)
 	p.Ctxt = Ctxt
 	return p
 }

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

@@ -16,9 +16,7 @@ import (
 )
 
 // architecture-independent object file output
-const (
-	ArhdrSize = 60
-)
+const ArhdrSize = 60
 
 func formathdr(arhdr []byte, name string, size int64) {
 	copy(arhdr[:], fmt.Sprintf("%-16s%-12d%-6d%-6d%-8o%-10d`\n", name, 0, 0, 0, 0644, size))
@@ -62,6 +60,7 @@ func dumpobj1(outfile string, mode int) {
 		fmt.Printf("can't create %s: %v\n", outfile, err)
 		errorexit()
 	}
+	defer bout.Close()
 
 	startobj := int64(0)
 	var arhdr [ArhdrSize]byte
@@ -108,7 +107,6 @@ func dumpobj1(outfile string, mode int) {
 	}
 
 	if mode&modeLinkerObj == 0 {
-		bout.Close()
 		return
 	}
 
@@ -170,8 +168,6 @@ func dumpobj1(outfile string, mode int) {
 		formathdr(arhdr[:], "_go_.o", size)
 		bout.Write(arhdr[:])
 	}
-
-	bout.Close()
 }
 
 func addptabs() {

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

@@ -156,8 +156,7 @@ func walkselect(sel *Node) {
 			a.Nbody.Set1(mkcall("block", nil, &ln))
 			l = ln.Slice()
 			a = typecheck(a, Etop)
-			l = append(l, a)
-			l = append(l, n)
+			l = append(l, a, n)
 		}
 
 		l = append(l, cas.Nbody.Slice()...)

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

@@ -5119,10 +5119,11 @@ func (e *ssafn) DerefItab(it *obj.LSym, offset int64) *obj.LSym {
 func (e *ssafn) splitSlot(parent *ssa.LocalSlot, suffix string, offset int64, t *types.Type) ssa.LocalSlot {
 	s := &types.Sym{Name: parent.N.(*Node).Sym.Name + suffix, Pkg: localpkg}
 
-	n := new(Node)
-	n.Name = new(Name)
-	n.Op = ONAME
-	n.Pos = parent.N.(*Node).Pos
+	n := &Node{
+		Name: new(Name),
+		Op:   ONAME,
+		Pos:  parent.N.(*Node).Pos,
+	}
 	n.Orig = n
 
 	s.Def = asTypesNode(n)

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

@@ -1130,48 +1130,42 @@ func updateHasCall(n *Node) {
 	if n == nil {
 		return
 	}
+	n.SetHasCall(calcHasCall(n))
+}
 
-	b := false
+func calcHasCall(n *Node) bool {
 	if n.Ninit.Len() != 0 {
 		// TODO(mdempsky): This seems overly conservative.
-		b = true
-		goto out
+		return true
 	}
 
 	switch n.Op {
 	case OLITERAL, ONAME, OTYPE:
-		if b || n.HasCall() {
+		if n.HasCall() {
 			Fatalf("OLITERAL/ONAME/OTYPE should never have calls: %+v", n)
 		}
-		return
+		return false
 	case OCALL, OCALLFUNC, OCALLMETH, OCALLINTER:
-		b = true
-		goto out
+		return true
 	case OANDAND, OOROR:
 		// hard with instrumented code
 		if instrumenting {
-			b = true
-			goto out
+			return true
 		}
 	case OINDEX, OSLICE, OSLICEARR, OSLICE3, OSLICE3ARR, OSLICESTR,
 		OIND, ODOTPTR, ODOTTYPE, ODIV, OMOD:
 		// These ops might panic, make sure they are done
 		// before we start marshaling args for a call. See issue 16760.
-		b = true
-		goto out
+		return true
 	}
 
 	if n.Left != nil && n.Left.HasCall() {
-		b = true
-		goto out
+		return true
 	}
 	if n.Right != nil && n.Right.HasCall() {
-		b = true
-		goto out
+		return true
 	}
-
-out:
-	n.SetHasCall(b)
+	return false
 }
 
 func badtype(op Op, tl *types.Type, tr *types.Type) {
@@ -1383,6 +1377,7 @@ func adddot1(s *types.Sym, t *types.Type, d int, save **types.Field, ignorecase
 		return
 	}
 	t.SetRecur(true)
+	defer t.SetRecur(false)
 
 	var u *types.Type
 	d--
@@ -1392,7 +1387,7 @@ func adddot1(s *types.Sym, t *types.Type, d int, save **types.Field, ignorecase
 		// below for embedded fields.
 		c = lookdot0(s, t, save, ignorecase)
 		if c != 0 {
-			goto out
+			return c, false
 		}
 	}
 
@@ -1401,7 +1396,7 @@ func adddot1(s *types.Sym, t *types.Type, d int, save **types.Field, ignorecase
 		u = u.Elem()
 	}
 	if !u.IsStruct() && !u.IsInterface() {
-		goto out
+		return c, false
 	}
 
 	for _, f := range u.Fields().Slice() {
@@ -1410,8 +1405,7 @@ func adddot1(s *types.Sym, t *types.Type, d int, save **types.Field, ignorecase
 		}
 		if d < 0 {
 			// Found an embedded field at target depth.
-			more = true
-			goto out
+			return c, true
 		}
 		a, more1 := adddot1(s, f.Type, d, save, ignorecase)
 		if a != 0 && c == 0 {
@@ -1423,8 +1417,6 @@ func adddot1(s *types.Sym, t *types.Type, d int, save **types.Field, ignorecase
 		}
 	}
 
-out:
-	t.SetRecur(false)
 	return c, more
 }
 
@@ -1553,10 +1545,7 @@ func expand1(t *types.Type, top, followptr bool) {
 		u = u.Elem()
 	}
 
-	if !u.IsStruct() && !u.IsInterface() {
-		goto out
-	}
-
+	if u.IsStruct() || u.IsInterface() {
 		for _, f := range u.Fields().Slice() {
 			if f.Embedded == 0 {
 				continue
@@ -1566,8 +1555,8 @@ func expand1(t *types.Type, top, followptr bool) {
 			}
 			expand1(f.Type, false, followptr)
 		}
+	}
 
-out:
 	t.SetRecur(false)
 }
 

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

@@ -13,9 +13,7 @@ import (
 )
 
 // The constant is known to runtime.
-const (
-	tmpstringbufsize = 32
-)
+const tmpstringbufsize = 32
 
 func walk(fn *Node) {
 	Curfn = fn
@@ -2247,24 +2245,23 @@ func convas(n *Node, init *Nodes) *Node {
 	if n.Op != OAS {
 		Fatalf("convas: not OAS %v", n.Op)
 	}
+	defer updateHasCall(n)
 
 	n.SetTypecheck(1)
 
-	var lt *types.Type
-	var rt *types.Type
 	if n.Left == nil || n.Right == nil {
-		goto out
+		return n
 	}
 
-	lt = n.Left.Type
-	rt = n.Right.Type
+	lt := n.Left.Type
+	rt := n.Right.Type
 	if lt == nil || rt == nil {
-		goto out
+		return n
 	}
 
 	if isblank(n.Left) {
 		n.Right = defaultlit(n.Right, nil)
-		goto out
+		return n
 	}
 
 	if !eqtype(lt, rt) {
@@ -2273,8 +2270,6 @@ func convas(n *Node, init *Nodes) *Node {
 	}
 	dowidth(n.Right.Type)
 
-out:
-	updateHasCall(n)
 	return n
 }
 
@@ -2429,9 +2424,8 @@ func outervalue(n *Node) *Node {
 			}
 		}
 
-		break
-	}
 		return n
+	}
 }
 
 // Is it possible that the computation of n might be