cmd/compile: refactor constant node constructors

Passes toolstash-check.

Change-Id: I6a2d46e69d4d3a06858c80c4ea1ad3f5a58f6956
Reviewed-on: https://go-review.googlesource.com/103859
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -1246,6 +1246,7 @@ illegal:
 	}
 }
 
+// nodlit returns a new untyped constant with value v.
 func nodlit(v Val) *Node {
 	n := nod(OLITERAL, nil, nil)
 	n.SetVal(v)

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

@@ -413,21 +413,15 @@ func (x methcmp) Less(i, j int) bool {
 }
 
 func nodintconst(v int64) *Node {
-	c := nod(OLITERAL, nil, nil)
-	c.SetAddable(true)
-	c.SetVal(Val{new(Mpint)})
-	c.Val().U.(*Mpint).SetInt64(v)
-	c.Type = types.Types[TIDEAL]
-	return c
+	u := new(Mpint)
+	u.SetInt64(v)
+	return nodlit(Val{u})
 }
 
 func nodfltconst(v *Mpflt) *Node {
-	c := nod(OLITERAL, nil, nil)
-	c.SetAddable(true)
-	c.SetVal(Val{newMpflt()})
-	c.Val().U.(*Mpflt).Set(v)
-	c.Type = types.Types[TIDEAL]
-	return c
+	u := newMpflt()
+	u.Set(v)
+	return nodlit(Val{u})
 }
 
 func nodconst(n *Node, t *types.Type, v int64) {
@@ -444,17 +438,11 @@ func nodconst(n *Node, t *types.Type, v int64) {
 }
 
 func nodnil() *Node {
-	c := nodintconst(0)
-	c.SetVal(Val{new(NilVal)})
-	c.Type = types.Types[TNIL]
-	return c
+	return nodlit(Val{new(NilVal)})
 }
 
 func nodbool(b bool) *Node {
-	c := nodintconst(0)
-	c.SetVal(Val{b})
-	c.Type = types.Idealbool
-	return c
+	return nodlit(Val{b})
 }
 
 func nodstr(s string) *Node {