cmd/compile/internal/gc: remove remaining Nod(OXXX, ...)

Remove almost all the remaining Nod(OXXX, ... ) uses. The performance
change is due entirely to the changes to func temp(*Type). The other
cleanups have no effect, as expected.

I'll address the remaining Nod(OXXX, ...) uses in a followup CL as they
are very sensitive to change.

lucky(~/go/src/cmd/compile) % benchstat /tmp/{old,new}.txt
name      old time/op    new time/op    delta
Template     391ms ± 6%     385ms ± 6%    ~     (p=0.127 n=19+20)
GoTypes      1.27s ± 2%     1.27s ± 2%    ~     (p=0.172 n=19+19)
Compiler     6.17s ± 2%     6.15s ± 2%    ~     (p=0.647 n=19+20)

name      old alloc/op   new alloc/op   delta
Template    63.7MB ± 0%    63.4MB ± 0%  -0.35%  (p=0.000 n=16+20)
GoTypes      219MB ± 0%     218MB ± 0%  -0.38%  (p=0.000 n=20+20)
Compiler     980MB ± 0%     976MB ± 0%  -0.38%  (p=0.000 n=20+20)

name      old allocs/op  new allocs/op  delta
Template      586k ± 0%      584k ± 0%  -0.30%  (p=0.000 n=20+20)
GoTypes      1.80M ± 0%     1.79M ± 0%  -0.31%  (p=0.000 n=20+20)
Compiler     7.74M ± 0%     7.71M ± 0%  -0.34%  (p=0.000 n=20+20)

Change-Id: Ie21a5443c33a23ce30f987bdddec9fe350365d35
Reviewed-on: https://go-review.googlesource.com/21017Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -117,9 +117,8 @@ func convlit1(n *Node, t *Type, explicit bool) *Node {
 	}
 
 	if n.Op == OLITERAL {
-		nn := Nod(OXXX, nil, nil)
-		*nn = *n
-		n = nn
+		nn := *n
+		n = &nn
 	}
 
 	switch n.Op {
@@ -559,11 +558,10 @@ func evconst(n *Node) {
 					i2++
 				}
 
-				nl := Nod(OXXX, nil, nil)
-				*nl = *s[i1]
-				nl.Orig = nl
+				nl := *s[i1]
+				nl.Orig = &nl
 				nl.SetVal(Val{strings.Join(strs, "")})
-				s[i1] = nl
+				s[i1] = &nl
 				s = append(s[:i1+1], s[i2:]...)
 			}
 		}
@@ -1250,9 +1248,8 @@ func defaultlit(n *Node, t *Type) *Node {
 	}
 
 	if n.Op == OLITERAL {
-		nn := Nod(OXXX, nil, nil)
-		*nn = *n
-		n = nn
+		nn := *n
+		n = &nn
 	}
 
 	lno := setlineno(n)

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

@@ -605,7 +605,6 @@ func funcargs(nt *Node) {
 	// declare the out arguments.
 	gen := nt.List.Len()
 	var i int = 0
-	var nn *Node
 	for _, n = range nt.Rlist.Slice() {
 		if n.Op != ODCLFIELD {
 			Fatalf("funcargs out %v", Oconv(n.Op, 0))
@@ -629,13 +628,11 @@ func funcargs(nt *Node) {
 			// So the two cases must be distinguished.
 			// We do not record a pointer to the original node (n->orig).
 			// Having multiple names causes too much confusion in later passes.
-			nn = Nod(OXXX, nil, nil)
-
-			*nn = *n.Left
-			nn.Orig = nn
+			nn := *n.Left
+			nn.Orig = &nn
 			nn.Sym = LookupN("~b", gen)
 			gen++
-			n.Left = nn
+			n.Left = &nn
 		}
 
 		n.Left.Name.Param.Ntype = n.Right

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

@@ -522,9 +522,8 @@ func importconst(s *Sym, t *Type, n *Node) {
 	}
 
 	if n.Sym != nil {
-		n1 := Nod(OXXX, nil, nil)
-		*n1 = *n
-		n = n1
+		n1 := *n
+		n = &n1
 	}
 
 	n.Orig = newname(s)

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

@@ -613,8 +613,8 @@ func Tempname(nn *Node, t *Type) {
 }
 
 func temp(t *Type) *Node {
-	n := Nod(OXXX, nil, nil)
-	Tempname(n, t)
+	var n Node
+	Tempname(&n, t)
 	n.Sym.Def.Used = true
 	return n.Orig
 }

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

@@ -249,8 +249,7 @@ func inlcopy(n *Node) *Node {
 		return n
 	}
 
-	m := Nod(OXXX, nil, nil)
-	*m = *n
+	m := *n
 	if m.Func != nil {
 		m.Func.Inl.Set(nil)
 	}
@@ -261,7 +260,7 @@ func inlcopy(n *Node) *Node {
 	m.Ninit.Set(inlcopylist(n.Ninit.Slice()))
 	m.Nbody.Set(inlcopylist(n.Nbody.Slice()))
 
-	return m
+	return &m
 }
 
 // Inlcalls/nodelist/node walks fn's statements and expressions and substitutes any
@@ -968,8 +967,7 @@ func (subst *inlsubst) node(n *Node) *Node {
 		m.Left = newname(Lookup(p))
 
 		return m
-	}
-
+	default:
 		m := Nod(OXXX, nil, nil)
 		*m = *n
 		m.Ninit.Set(nil)
@@ -986,6 +984,7 @@ func (subst *inlsubst) node(n *Node) *Node {
 		m.Nbody.Set(subst.list(n.Nbody))
 
 		return m
+	}
 }
 
 // Plaster over linenumbers

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

@@ -107,12 +107,10 @@ func ordercheapexpr(n *Node, order *Order) *Node {
 		if l == n.Left {
 			return n
 		}
-		a := Nod(OXXX, nil, nil)
-		*a = *n
-		a.Orig = a
+		a := *n
+		a.Orig = &a
 		a.Left = l
-		a = typecheck(a, Erv)
-		return a
+		return typecheck(&a, Erv)
 	}
 
 	return ordercopyexpr(n, n.Type, order, 0)
@@ -135,24 +133,20 @@ func ordersafeexpr(n *Node, order *Order) *Node {
 		if l == n.Left {
 			return n
 		}
-		a := Nod(OXXX, nil, nil)
-		*a = *n
-		a.Orig = a
+		a := *n
+		a.Orig = &a
 		a.Left = l
-		a = typecheck(a, Erv)
-		return a
+		return typecheck(&a, Erv)
 
 	case ODOTPTR, OIND:
 		l := ordercheapexpr(n.Left, order)
 		if l == n.Left {
 			return n
 		}
-		a := Nod(OXXX, nil, nil)
-		*a = *n
-		a.Orig = a
+		a := *n
+		a.Orig = &a
 		a.Left = l
-		a = typecheck(a, Erv)
-		return a
+		return typecheck(&a, Erv)
 
 	case OINDEX, OINDEXMAP:
 		var l *Node
@@ -165,17 +159,15 @@ func ordersafeexpr(n *Node, order *Order) *Node {
 		if l == n.Left && r == n.Right {
 			return n
 		}
-		a := Nod(OXXX, nil, nil)
-		*a = *n
-		a.Orig = a
+		a := *n
+		a.Orig = &a
 		a.Left = l
 		a.Right = r
-		a = typecheck(a, Erv)
-		return a
-	}
-
+		return typecheck(&a, Erv)
+	default:
 		Fatalf("ordersafeexpr %v", Oconv(n.Op, 0))
 		return nil // not reached
+	}
 }
 
 // Istemp reports whether n is a temporary variable.

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

@@ -65,12 +65,10 @@ func instrument(fn *Node) {
 		// nodpc is the PC of the caller as extracted by
 		// getcallerpc. We use -widthptr(FP) for x86.
 		// BUG: this will not work on arm.
-		nodpc := Nod(OXXX, nil, nil)
-
-		*nodpc = *nodfp
+		nodpc := *nodfp
 		nodpc.Type = Types[TUINTPTR]
 		nodpc.Xoffset = int64(-Widthptr)
-		nd := mkcall("racefuncenter", nil, nil, nodpc)
+		nd := mkcall("racefuncenter", nil, nil, &nodpc)
 		fn.Func.Enter.Set(append([]*Node{nd}, fn.Func.Enter.Slice()...))
 		nd = mkcall("racefuncexit", nil, nil)
 		fn.Func.Exit.Append(nd)

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

@@ -516,12 +516,10 @@ func treecopy(n *Node, lineno int32) *Node {
 		return nil
 	}
 
-	var m *Node
 	switch n.Op {
 	default:
-		m = Nod(OXXX, nil, nil)
-		*m = *n
-		m.Orig = m
+		m := *n
+		m.Orig = &m
 		m.Left = treecopy(n.Left, lineno)
 		m.Right = treecopy(n.Right, lineno)
 		m.List.Set(listtreecopy(n.List.Slice(), lineno))
@@ -532,6 +530,7 @@ func treecopy(n *Node, lineno int32) *Node {
 			Dump("treecopy", n)
 			Fatalf("treecopy Name")
 		}
+		return &m
 
 	case ONONAME:
 		if n.Sym == Lookup("iota") {
@@ -539,23 +538,20 @@ func treecopy(n *Node, lineno int32) *Node {
 			// but make a copy of the Node* just in case,
 			// so that all the copies of this const definition
 			// don't have the same iota value.
-			m = Nod(OXXX, nil, nil)
-			*m = *n
+			m := *n
 			if lineno != 0 {
 				m.Lineno = lineno
 			}
 			m.Name = new(Name)
 			*m.Name = *n.Name
 			m.Name.Iota = iota_
-			break
+			return &m
 		}
-		fallthrough
+		return n
 
 	case ONAME, OLITERAL, OTYPE:
-		m = n
+		return n
 	}
-
-	return m
 }
 
 // isnil reports whether n represents the universal untyped zero value "nil".
@@ -1085,8 +1081,7 @@ func assignconvfn(n *Node, t *Type, context func() string) *Node {
 // The result of substArgTypes MUST be assigned back to old, e.g.
 // 	n.Left = substArgTypes(n.Left, t1, t2)
 func substArgTypes(old *Node, types ...*Type) *Node {
-	n := Nod(OXXX, nil, nil)
-	*n = *old // make shallow copy
+	n := *old // make shallow copy
 
 	for _, t := range types {
 		dowidth(t)
@@ -1095,7 +1090,7 @@ func substArgTypes(old *Node, types ...*Type) *Node {
 	if len(types) > 0 {
 		Fatalf("substArgTypes: too many argument types")
 	}
-	return n
+	return &n
 }
 
 // substAny walks t, replacing instances of "any" with successive