[dev.cc] cmd/5g etc: code cleanup: delay var decls and eliminate dead code

Ran rsc.io/grind rev 6f0e601 on the source files.

The cleanups move var declarations as close to the use
as possible, splitting disjoint uses of the var into separate
variables. They also remove dead code (especially in
func sudoaddable), which helps with the var moving.

There's more cleanup to come, but this alone cuts the
time spent compiling html/template on my 2013 MacBook Pro
from 3.1 seconds to 2.3 seconds.

Change-Id: I4de499f47b1dd47a560c310bbcde6b08d425cfd6
Reviewed-on: https://go-review.googlesource.com/5637
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 41 insertions, 64 deletions

diff --git a/src/cmd/internal/gc/range.go b/src/cmd/internal/gc/range.go
index bb30bcf283..616c859a5a 100644
--- a/src/cmd/internal/gc/range.go
+++ b/src/cmd/internal/gc/range.go
@@ -12,12 +12,10 @@ import "cmd/internal/obj"
 func typecheckrange(n *Node) {
 	var toomany int
 	var why string
-	var t *Type
 	var t1 *Type
 	var t2 *Type
 	var v1 *Node
 	var v2 *Node
-	var ll *NodeList
 
 	// Typechecking order is important here:
 	// 0. first typecheck range expression (slice/map/chan),
@@ -31,13 +29,13 @@ func typecheckrange(n *Node) {
 
 	typecheck(&n.Right, Erv)
 
-	t = n.Right.Type
+	t := n.Right.Type
 	if t == nil {
 		goto out
 	}
 
 	// delicate little dance.  see typecheckas2
-	for ll = n.List; ll != nil; ll = ll.Next {
+	for ll := n.List; ll != nil; ll = ll.Next {
 		if ll.N.Defn != n {
 			typecheck(&ll.N, Erv|Easgn)
 		}
@@ -125,7 +123,7 @@ func typecheckrange(n *Node) {
 out:
 	n.Typecheck = 1
 
-	for ll = n.List; ll != nil; ll = ll.Next {
+	for ll := n.List; ll != nil; ll = ll.Next {
 		if ll.N.Typecheck == 0 {
 			typecheck(&ll.N, Erv|Easgn)
 		}
@@ -137,40 +135,17 @@ out:
 }
 
 func walkrange(n *Node) {
-	var ohv1 *Node
-	var hv1 *Node // hidden (old) val 1, 2 // hidden aggregate, iterator // hidden len, pointer // hidden bool // not hidden aggregate, val 1, 2
-	var hv2 *Node
-	var ha *Node
-	var hit *Node
-	var hn *Node
-	var hp *Node
-	var hb *Node
-	var a *Node
-	var v1 *Node
-	var v2 *Node
-	var fn *Node
-	var tmp *Node
-	var keyname *Node
-	var valname *Node
-	var key *Node
-	var val *Node
-	var body *NodeList
-	var init *NodeList
-	var th *Type
-	var t *Type
-	var lno int
+	t := n.Type
+	init := (*NodeList)(nil)
 
-	t = n.Type
-	init = nil
+	a := n.Right
+	lno := int(setlineno(a))
 
-	a = n.Right
-	lno = int(setlineno(a))
-
-	v1 = nil
+	v1 := (*Node)(nil)
 	if n.List != nil {
 		v1 = n.List.N
 	}
-	v2 = nil
+	v2 := (*Node)(nil)
 	if n.List != nil && n.List.Next != nil && !isblank(n.List.Next.N) {
 		v2 = n.List.Next.N
 	}
@@ -179,8 +154,9 @@ func walkrange(n *Node) {
 	// to avoid erroneous processing by racewalk.
 	n.List = nil
 
-	hv2 = nil
+	hv2 := (*Node)(nil)
 
+	var body *NodeList
 	switch t.Etype {
 	default:
 		Fatal("walkrange")
@@ -202,7 +178,7 @@ func walkrange(n *Node) {
 						if n.Nbody != nil {
 							if n.Nbody.N != nil { // at least one statement in body
 								if n.Nbody.Next == nil { // at most one statement in body
-									tmp = n.Nbody.N // first statement of body
+									tmp := n.Nbody.N // first statement of body
 									if tmp.Op == OAS {
 										if tmp.Left.Op == OINDEX {
 											if samesafeexpr(tmp.Left.Left, a) {
@@ -223,9 +199,9 @@ func walkrange(n *Node) {
 															n.Nincr = nil
 
 															// hp = &a[0]
-															hp = temp(Ptrto(Types[TUINT8]))
+															hp := temp(Ptrto(Types[TUINT8]))
 
-															tmp = Nod(OINDEX, a, Nodintconst(0))
+															tmp := Nod(OINDEX, a, Nodintconst(0))
 															tmp.Bounded = true
 															tmp = Nod(OADDR, tmp, nil)
 															tmp = Nod(OCONVNOP, tmp, nil)
@@ -233,7 +209,7 @@ func walkrange(n *Node) {
 															n.Nbody = list(n.Nbody, Nod(OAS, hp, tmp))
 
 															// hn = len(a) * sizeof(elem(a))
-															hn = temp(Types[TUINTPTR])
+															hn := temp(Types[TUINTPTR])
 
 															tmp = Nod(OLEN, a, nil)
 															tmp = Nod(OMUL, tmp, Nodintconst(t.Type.Width))
@@ -241,7 +217,7 @@ func walkrange(n *Node) {
 															n.Nbody = list(n.Nbody, Nod(OAS, hn, tmp))
 
 															// memclr(hp, hn)
-															fn = mkcall("memclr", nil, nil, hp, hn)
+															fn := mkcall("memclr", nil, nil, hp, hn)
 
 															n.Nbody = list(n.Nbody, fn)
 
@@ -270,17 +246,17 @@ func walkrange(n *Node) {
 		}
 
 		// orderstmt arranged for a copy of the array/slice variable if needed.
-		ha = a
+		ha := a
 
-		hv1 = temp(Types[TINT])
-		hn = temp(Types[TINT])
-		hp = nil
+		hv1 := temp(Types[TINT])
+		hn := temp(Types[TINT])
+		hp := (*Node)(nil)
 
 		init = list(init, Nod(OAS, hv1, nil))
 		init = list(init, Nod(OAS, hn, Nod(OLEN, ha, nil)))
 		if v2 != nil {
 			hp = temp(Ptrto(n.Type.Type))
-			tmp = Nod(OINDEX, ha, Nodintconst(0))
+			tmp := Nod(OINDEX, ha, Nodintconst(0))
 			tmp.Bounded = true
 			init = list(init, Nod(OAS, hp, Nod(OADDR, tmp, nil)))
 		}
@@ -292,7 +268,7 @@ func walkrange(n *Node) {
 		} else if v2 == nil {
 			body = list1(Nod(OAS, v1, hv1))
 		} else {
-			a = Nod(OAS2, nil, nil)
+			a := Nod(OAS2, nil, nil)
 			a.List = list(list1(v1), v2)
 			a.Rlist = list(list1(hv1), Nod(OIND, hp, nil))
 			body = list1(a)
@@ -305,7 +281,7 @@ func walkrange(n *Node) {
 			// Advancing during the increment ensures that the pointer p only points
 			// pass the end of the array during the final "p++; i++; if(i >= len(x)) break;",
 			// after which p is dead, so it cannot confuse the collector.
-			tmp = Nod(OADD, hp, Nodintconst(t.Type.Width))
+			tmp := Nod(OADD, hp, Nodintconst(t.Type.Width))
 
 			tmp.Type = hp.Type
 			tmp.Typecheck = 1
@@ -319,16 +295,16 @@ func walkrange(n *Node) {
 		// orderstmt allocated the iterator for us.
 	// we only use a once, so no copy needed.
 	case TMAP:
-		ha = a
+		ha := a
 
-		th = hiter(t)
-		hit = n.Alloc
+		th := hiter(t)
+		hit := n.Alloc
 		hit.Type = th
 		n.Left = nil
-		keyname = newname(th.Type.Sym)      // depends on layout of iterator struct.  See reflect.c:hiter
-		valname = newname(th.Type.Down.Sym) // ditto
+		keyname := newname(th.Type.Sym)      // depends on layout of iterator struct.  See reflect.c:hiter
+		valname := newname(th.Type.Down.Sym) // ditto
 
-		fn = syslook("mapiterinit", 1)
+		fn := syslook("mapiterinit", 1)
 
 		argtype(fn, t.Down)
 		argtype(fn, t.Type)
@@ -340,16 +316,16 @@ func walkrange(n *Node) {
 		argtype(fn, th)
 		n.Nincr = mkcall1(fn, nil, nil, Nod(OADDR, hit, nil))
 
-		key = Nod(ODOT, hit, keyname)
+		key := Nod(ODOT, hit, keyname)
 		key = Nod(OIND, key, nil)
 		if v1 == nil {
 			body = nil
 		} else if v2 == nil {
 			body = list1(Nod(OAS, v1, key))
 		} else {
-			val = Nod(ODOT, hit, valname)
+			val := Nod(ODOT, hit, valname)
 			val = Nod(OIND, val, nil)
-			a = Nod(OAS2, nil, nil)
+			a := Nod(OAS2, nil, nil)
 			a.List = list(list1(v1), v2)
 			a.Rlist = list(list1(key), val)
 			body = list1(a)
@@ -357,19 +333,19 @@ func walkrange(n *Node) {
 
 		// orderstmt arranged for a copy of the channel variable.
 	case TCHAN:
-		ha = a
+		ha := a
 
 		n.Ntest = nil
 
-		hv1 = temp(t.Type)
+		hv1 := temp(t.Type)
 		hv1.Typecheck = 1
 		if haspointers(t.Type) {
 			init = list(init, Nod(OAS, hv1, nil))
 		}
-		hb = temp(Types[TBOOL])
+		hb := temp(Types[TBOOL])
 
 		n.Ntest = Nod(ONE, hb, Nodbool(false))
-		a = Nod(OAS2RECV, nil, nil)
+		a := Nod(OAS2RECV, nil, nil)
 		a.Typecheck = 1
 		a.List = list(list1(hv1), hb)
 		a.Rlist = list1(Nod(ORECV, ha, nil))
@@ -382,20 +358,21 @@ func walkrange(n *Node) {
 
 		// orderstmt arranged for a copy of the string variable.
 	case TSTRING:
-		ha = a
+		ha := a
 
-		ohv1 = temp(Types[TINT])
+		ohv1 := temp(Types[TINT])
 
-		hv1 = temp(Types[TINT])
+		hv1 := temp(Types[TINT])
 		init = list(init, Nod(OAS, hv1, nil))
 
+		var a *Node
 		if v2 == nil {
 			a = Nod(OAS, hv1, mkcall("stringiter", Types[TINT], nil, ha, hv1))
 		} else {
 			hv2 = temp(runetype)
 			a = Nod(OAS2, nil, nil)
 			a.List = list(list1(hv1), hv2)
-			fn = syslook("stringiter2", 0)
+			fn := syslook("stringiter2", 0)
 			a.Rlist = list1(mkcall1(fn, getoutargx(fn.Type), nil, ha, hv1))
 		}