diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go
index c2ed0d31d8..68bcae3f4c 100644
--- a/src/cmd/compile/internal/gc/const.go
+++ b/src/cmd/compile/internal/gc/const.go
@@ -378,22 +378,22 @@ bad:
 }
 
 func copyval(v Val) Val {
-	switch v.Ctype() {
-	case CTINT, CTRUNE:
+	switch u := v.U.(type) {
+	case *Mpint:
 		i := new(Mpint)
-		i.Set(v.U.(*Mpint))
-		i.Rune = v.U.(*Mpint).Rune
+		i.Set(u)
+		i.Rune = u.Rune
 		v.U = i
 
-	case CTFLT:
+	case *Mpflt:
 		f := newMpflt()
-		f.Set(v.U.(*Mpflt))
+		f.Set(u)
 		v.U = f
 
-	case CTCPLX:
+	case *Mpcplx:
 		c := new(Mpcplx)
-		c.Real.Set(&v.U.(*Mpcplx).Real)
-		c.Imag.Set(&v.U.(*Mpcplx).Imag)
+		c.Real.Set(&u.Real)
+		c.Imag.Set(&u.Imag)
 		v.U = c
 	}
 
@@ -401,16 +401,16 @@ func copyval(v Val) Val {
 }
 
 func tocplx(v Val) Val {
-	switch v.Ctype() {
-	case CTINT, CTRUNE:
+	switch u := v.U.(type) {
+	case *Mpint:
 		c := new(Mpcplx)
-		c.Real.SetInt(v.U.(*Mpint))
+		c.Real.SetInt(u)
 		c.Imag.SetFloat64(0.0)
 		v.U = c
 
-	case CTFLT:
+	case *Mpflt:
 		c := new(Mpcplx)
-		c.Real.Set(v.U.(*Mpflt))
+		c.Real.Set(u)
 		c.Imag.SetFloat64(0.0)
 		v.U = c
 	}
@@ -419,17 +419,17 @@ func tocplx(v Val) Val {
 }
 
 func toflt(v Val) Val {
-	switch v.Ctype() {
-	case CTINT, CTRUNE:
+	switch u := v.U.(type) {
+	case *Mpint:
 		f := newMpflt()
-		f.SetInt(v.U.(*Mpint))
+		f.SetInt(u)
 		v.U = f
 
-	case CTCPLX:
+	case *Mpcplx:
 		f := newMpflt()
-		f.Set(&v.U.(*Mpcplx).Real)
-		if v.U.(*Mpcplx).Imag.CmpFloat64(0) != 0 {
-			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.(*Mpcplx).Real, FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, FmtSharp|FmtSign))
+		f.Set(&u.Real)
+		if u.Imag.CmpFloat64(0) != 0 {
+			Yyerror("constant %v%vi truncated to real", Fconv(&u.Real, FmtSharp), Fconv(&u.Imag, FmtSharp|FmtSign))
 		}
 		v.U = f
 	}
@@ -438,31 +438,33 @@ func toflt(v Val) Val {
 }
 
 func toint(v Val) Val {
-	switch v.Ctype() {
-	case CTRUNE:
-		i := new(Mpint)
-		i.Set(v.U.(*Mpint))
-		v.U = i
+	switch u := v.U.(type) {
+	case *Mpint:
+		if u.Rune {
+			i := new(Mpint)
+			i.Set(u)
+			v.U = i
+		}
 
-	case CTFLT:
+	case *Mpflt:
 		i := new(Mpint)
-		if f := v.U.(*Mpflt); i.SetFloat(f) < 0 {
+		if i.SetFloat(u) < 0 {
 			msg := "constant %v truncated to integer"
 			// provide better error message if SetFloat failed because f was too large
-			if f.Val.IsInt() {
+			if u.Val.IsInt() {
 				msg = "constant %v overflows integer"
 			}
-			Yyerror(msg, Fconv(f, FmtSharp))
+			Yyerror(msg, Fconv(u, FmtSharp))
 		}
 		v.U = i
 
-	case CTCPLX:
+	case *Mpcplx:
 		i := new(Mpint)
-		if i.SetFloat(&v.U.(*Mpcplx).Real) < 0 {
-			Yyerror("constant %v%vi truncated to integer", Fconv(&v.U.(*Mpcplx).Real, FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, FmtSharp|FmtSign))
+		if i.SetFloat(&u.Real) < 0 {
+			Yyerror("constant %v%vi truncated to integer", Fconv(&u.Real, FmtSharp), Fconv(&u.Imag, FmtSharp|FmtSign))
 		}
-		if v.U.(*Mpcplx).Imag.CmpFloat64(0) != 0 {
-			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.(*Mpcplx).Real, FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, FmtSharp|FmtSign))
+		if u.Imag.CmpFloat64(0) != 0 {
+			Yyerror("constant %v%vi truncated to real", Fconv(&u.Real, FmtSharp), Fconv(&u.Imag, FmtSharp|FmtSign))
 		}
 		v.U = i
 	}
@@ -471,30 +473,25 @@ func toint(v Val) Val {
 }
 
 func doesoverflow(v Val, t *Type) bool {
-	switch v.Ctype() {
-	case CTINT, CTRUNE:
+	switch u := v.U.(type) {
+	case *Mpint:
 		if !t.IsInteger() {
 			Fatalf("overflow: %v integer constant", t)
 		}
-		if v.U.(*Mpint).Cmp(Minintval[t.Etype]) < 0 || v.U.(*Mpint).Cmp(Maxintval[t.Etype]) > 0 {
-			return true
-		}
+		return u.Cmp(Minintval[t.Etype]) < 0 || u.Cmp(Maxintval[t.Etype]) > 0
 
-	case CTFLT:
+	case *Mpflt:
 		if !t.IsFloat() {
 			Fatalf("overflow: %v floating-point constant", t)
 		}
-		if v.U.(*Mpflt).Cmp(minfltval[t.Etype]) <= 0 || v.U.(*Mpflt).Cmp(maxfltval[t.Etype]) >= 0 {
-			return true
-		}
+		return u.Cmp(minfltval[t.Etype]) <= 0 || u.Cmp(maxfltval[t.Etype]) >= 0
 
-	case CTCPLX:
+	case *Mpcplx:
 		if !t.IsComplex() {
 			Fatalf("overflow: %v complex constant", t)
 		}
-		if v.U.(*Mpcplx).Real.Cmp(minfltval[t.Etype]) <= 0 || v.U.(*Mpcplx).Real.Cmp(maxfltval[t.Etype]) >= 0 || v.U.(*Mpcplx).Imag.Cmp(minfltval[t.Etype]) <= 0 || v.U.(*Mpcplx).Imag.Cmp(maxfltval[t.Etype]) >= 0 {
-			return true
-		}
+		return u.Real.Cmp(minfltval[t.Etype]) <= 0 || u.Real.Cmp(maxfltval[t.Etype]) >= 0 ||
+			u.Imag.Cmp(minfltval[t.Etype]) <= 0 || u.Imag.Cmp(maxfltval[t.Etype]) >= 0
 	}
 
 	return false
@@ -518,21 +515,16 @@ func overflow(v Val, t *Type) {
 }
 
 func tostr(v Val) Val {
-	switch v.Ctype() {
-	case CTINT, CTRUNE:
+	switch u := v.U.(type) {
+	case *Mpint:
 		var i int64 = 0xFFFD
-		if u := v.U.(*Mpint); u.Cmp(Minintval[TUINT32]) >= 0 && u.Cmp(Maxintval[TUINT32]) <= 0 {
+		if u.Cmp(Minintval[TUINT32]) >= 0 && u.Cmp(Maxintval[TUINT32]) <= 0 {
 			i = u.Int64()
 		}
-		v = Val{}
 		v.U = string(i)
 
-	case CTFLT:
-		Yyerror("no float -> string")
-		fallthrough
-
-	case CTNIL:
-		v = Val{}
+	case *NilVal:
+		// Can happen because of string([]byte(nil)).
 		v.U = ""
 	}
 
diff --git a/src/cmd/compile/internal/gc/cplx.go b/src/cmd/compile/internal/gc/cplx.go
index b0fa70b0ad..34fd0b96d9 100644
--- a/src/cmd/compile/internal/gc/cplx.go
+++ b/src/cmd/compile/internal/gc/cplx.go
@@ -89,8 +89,9 @@ func subnode(nr *Node, ni *Node, nc *Node) {
 	t := Types[tc]
 
 	if nc.Op == OLITERAL {
-		nodfconst(nr, t, &nc.Val().U.(*Mpcplx).Real)
-		nodfconst(ni, t, &nc.Val().U.(*Mpcplx).Imag)
+		u := nc.Val().U.(*Mpcplx)
+		nodfconst(nr, t, &u.Real)
+		nodfconst(ni, t, &u.Imag)
 		return
 	}
 
diff --git a/src/cmd/compile/internal/gc/dcl.go b/src/cmd/compile/internal/gc/dcl.go
index e303f11c09..7f6e167488 100644
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -755,17 +755,13 @@ func structfield(n *Node) *Field {
 		f.Broke = true
 	}
 
-	switch n.Val().Ctype() {
-	case CTSTR:
-		f.Note = new(string)
-		*f.Note = n.Val().U.(string)
-
+	switch u := n.Val().U.(type) {
+	case string:
+		f.Note = &u
 	default:
 		Yyerror("field annotation must be string")
-		fallthrough
-
-	case CTxxx:
-		f.Note = nil
+	case nil:
+		// noop
 	}
 
 	if n.Left != nil && n.Left.Op == ONAME {
diff --git a/src/cmd/compile/internal/gc/fmt.go b/src/cmd/compile/internal/gc/fmt.go
index e5977c0905..5f6edd1018 100644
--- a/src/cmd/compile/internal/gc/fmt.go
+++ b/src/cmd/compile/internal/gc/fmt.go
@@ -334,15 +334,16 @@ func Jconv(n *Node, flag FmtFlag) string {
 
 // Fmt "%V": Values
 func Vconv(v Val, flag FmtFlag) string {
-	switch v.Ctype() {
-	case CTINT:
-		if (flag&FmtSharp != 0) || fmtmode == FExp {
-			return Bconv(v.U.(*Mpint), FmtSharp)
+	switch u := v.U.(type) {
+	case *Mpint:
+		if !u.Rune {
+			if (flag&FmtSharp != 0) || fmtmode == FExp {
+				return Bconv(u, FmtSharp)
+			}
+			return Bconv(u, 0)
 		}
-		return Bconv(v.U.(*Mpint), 0)
 
-	case CTRUNE:
-		x := v.U.(*Mpint).Int64()
+		x := u.Int64()
 		if ' ' <= x && x < utf8.RuneSelf && x != '\\' && x != '\'' {
 			return fmt.Sprintf("'%c'", int(x))
 		}
@@ -352,39 +353,39 @@ func Vconv(v Val, flag FmtFlag) string {
 		if 0 <= x && x <= utf8.MaxRune {
 			return fmt.Sprintf("'\\U%08x'", uint64(x))
 		}
-		return fmt.Sprintf("('\\x00' + %v)", v.U.(*Mpint))
+		return fmt.Sprintf("('\\x00' + %v)", u)
 
-	case CTFLT:
+	case *Mpflt:
 		if (flag&FmtSharp != 0) || fmtmode == FExp {
-			return Fconv(v.U.(*Mpflt), 0)
+			return Fconv(u, 0)
 		}
-		return Fconv(v.U.(*Mpflt), FmtSharp)
+		return Fconv(u, FmtSharp)
 
-	case CTCPLX:
+	case *Mpcplx:
 		if (flag&FmtSharp != 0) || fmtmode == FExp {
-			return fmt.Sprintf("(%v+%vi)", &v.U.(*Mpcplx).Real, &v.U.(*Mpcplx).Imag)
+			return fmt.Sprintf("(%v+%vi)", &u.Real, &u.Imag)
 		}
 		if v.U.(*Mpcplx).Real.CmpFloat64(0) == 0 {
-			return fmt.Sprintf("%vi", Fconv(&v.U.(*Mpcplx).Imag, FmtSharp))
+			return fmt.Sprintf("%vi", Fconv(&u.Imag, FmtSharp))
 		}
 		if v.U.(*Mpcplx).Imag.CmpFloat64(0) == 0 {
-			return Fconv(&v.U.(*Mpcplx).Real, FmtSharp)
+			return Fconv(&u.Real, FmtSharp)
 		}
 		if v.U.(*Mpcplx).Imag.CmpFloat64(0) < 0 {
-			return fmt.Sprintf("(%v%vi)", Fconv(&v.U.(*Mpcplx).Real, FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, FmtSharp))
+			return fmt.Sprintf("(%v%vi)", Fconv(&u.Real, FmtSharp), Fconv(&u.Imag, FmtSharp))
 		}
-		return fmt.Sprintf("(%v+%vi)", Fconv(&v.U.(*Mpcplx).Real, FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, FmtSharp))
+		return fmt.Sprintf("(%v+%vi)", Fconv(&u.Real, FmtSharp), Fconv(&u.Imag, FmtSharp))
 
-	case CTSTR:
-		return strconv.Quote(v.U.(string))
+	case string:
+		return strconv.Quote(u)
 
-	case CTBOOL:
-		if v.U.(bool) {
+	case bool:
+		if u {
 			return "true"
 		}
 		return "false"
 
-	case CTNIL:
+	case *NilVal:
 		return "nil"
 	}
 
diff --git a/src/cmd/compile/internal/gc/gsubr.go b/src/cmd/compile/internal/gc/gsubr.go
index bcfd3439a0..ff6fbe42fb 100644
--- a/src/cmd/compile/internal/gc/gsubr.go
+++ b/src/cmd/compile/internal/gc/gsubr.go
@@ -430,28 +430,28 @@ func Naddr(a *obj.Addr, n *Node) {
 		if Thearch.LinkArch.Family == sys.I386 {
 			a.Width = 0
 		}
-		switch n.Val().Ctype() {
+		switch u := n.Val().U.(type) {
 		default:
 			Fatalf("naddr: const %v", Tconv(n.Type, FmtLong))
 
-		case CTFLT:
+		case *Mpflt:
 			a.Type = obj.TYPE_FCONST
-			a.Val = n.Val().U.(*Mpflt).Float64()
+			a.Val = u.Float64()
 
-		case CTINT, CTRUNE:
+		case *Mpint:
 			a.Sym = nil
 			a.Type = obj.TYPE_CONST
-			a.Offset = n.Int64()
+			a.Offset = u.Int64()
 
-		case CTSTR:
-			datagostring(n.Val().U.(string), a)
+		case string:
+			datagostring(u, a)
 
-		case CTBOOL:
+		case bool:
 			a.Sym = nil
 			a.Type = obj.TYPE_CONST
-			a.Offset = int64(obj.Bool2int(n.Val().U.(bool)))
+			a.Offset = int64(obj.Bool2int(u))
 
-		case CTNIL:
+		case *NilVal:
 			a.Sym = nil
 			a.Type = obj.TYPE_CONST
 			a.Offset = 0
diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index fab611fdb5..378ac0d2c3 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -342,20 +342,23 @@ func gdata(nam *Node, nr *Node, wid int) {
 
 	switch nr.Op {
 	case OLITERAL:
-		switch nr.Val().Ctype() {
-		case CTCPLX:
-			gdatacomplex(nam, nr.Val().U.(*Mpcplx))
+		switch u := nr.Val().U.(type) {
+		case *Mpcplx:
+			gdatacomplex(nam, u)
 
-		case CTSTR:
-			gdatastring(nam, nr.Val().U.(string))
+		case string:
+			gdatastring(nam, u)
 
-		case CTINT, CTRUNE, CTBOOL:
-			i, _ := nr.IntLiteral()
+		case bool:
+			i := int64(obj.Bool2int(u))
 			Linksym(nam.Sym).WriteInt(Ctxt, nam.Xoffset, wid, i)
 
-		case CTFLT:
+		case *Mpint:
+			Linksym(nam.Sym).WriteInt(Ctxt, nam.Xoffset, wid, u.Int64())
+
+		case *Mpflt:
 			s := Linksym(nam.Sym)
-			f := nr.Val().U.(*Mpflt).Float64()
+			f := u.Float64()
 			switch nam.Type.Etype {
 			case TFLOAT32:
 				s.WriteFloat32(Ctxt, nam.Xoffset, float32(f))
diff --git a/src/cmd/compile/internal/gc/parser.go b/src/cmd/compile/internal/gc/parser.go
index 6538877e68..ae4b497b7b 100644
--- a/src/cmd/compile/internal/gc/parser.go
+++ b/src/cmd/compile/internal/gc/parser.go
@@ -3246,17 +3246,14 @@ func (p *parser) hidden_literal() *Node {
 		if p.tok == LLITERAL {
 			ss := nodlit(p.val)
 			p.next()
-			switch ss.Val().Ctype() {
-			case CTINT, CTRUNE:
-				ss.Val().U.(*Mpint).Neg()
-				break
-			case CTFLT:
-				ss.Val().U.(*Mpflt).Neg()
-				break
-			case CTCPLX:
-				ss.Val().U.(*Mpcplx).Real.Neg()
-				ss.Val().U.(*Mpcplx).Imag.Neg()
-				break
+			switch u := ss.Val().U.(type) {
+			case *Mpint:
+				u.Neg()
+			case *Mpflt:
+				u.Neg()
+			case *Mpcplx:
+				u.Real.Neg()
+				u.Imag.Neg()
 			default:
 				Yyerror("bad negated constant")
 			}
diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go
index 71c06eb0a0..5560415cab 100644
--- a/src/cmd/compile/internal/gc/sinit.go
+++ b/src/cmd/compile/internal/gc/sinit.go
@@ -1309,28 +1309,22 @@ func addvalue(p *InitPlan, xoffset int64, n *Node) {
 func iszero(n *Node) bool {
 	switch n.Op {
 	case OLITERAL:
-		switch n.Val().Ctype() {
+		switch u := n.Val().U.(type) {
 		default:
 			Dump("unexpected literal", n)
 			Fatalf("iszero")
-
-		case CTNIL:
+		case *NilVal:
 			return true
-
-		case CTSTR:
-			return n.Val().U.(string) == ""
-
-		case CTBOOL:
-			return !n.Val().U.(bool)
-
-		case CTINT, CTRUNE:
-			return n.Val().U.(*Mpint).CmpInt64(0) == 0
-
-		case CTFLT:
-			return n.Val().U.(*Mpflt).CmpFloat64(0) == 0
-
-		case CTCPLX:
-			return n.Val().U.(*Mpcplx).Real.CmpFloat64(0) == 0 && n.Val().U.(*Mpcplx).Imag.CmpFloat64(0) == 0
+		case string:
+			return u == ""
+		case bool:
+			return !u
+		case *Mpint:
+			return u.CmpInt64(0) == 0
+		case *Mpflt:
+			return u.CmpFloat64(0) == 0
+		case *Mpcplx:
+			return u.Real.CmpFloat64(0) == 0 && u.Imag.CmpFloat64(0) == 0
 		}
 
 	case OARRAYLIT:
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 218f720a61..f989ad0375 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -1448,9 +1448,9 @@ func (s *state) expr(n *Node) *ssa.Value {
 		addr := s.addr(n, false)
 		return s.newValue2(ssa.OpLoad, n.Type, addr, s.mem())
 	case OLITERAL:
-		switch n.Val().Ctype() {
-		case CTINT:
-			i := n.Int64()
+		switch u := n.Val().U.(type) {
+		case *Mpint:
+			i := u.Int64()
 			switch n.Type.Size() {
 			case 1:
 				return s.constInt8(n.Type, int8(i))
@@ -1464,13 +1464,13 @@ func (s *state) expr(n *Node) *ssa.Value {
 				s.Fatalf("bad integer size %d", n.Type.Size())
 				return nil
 			}
-		case CTSTR:
-			if n.Val().U == "" {
+		case string:
+			if u == "" {
 				return s.constEmptyString(n.Type)
 			}
-			return s.entryNewValue0A(ssa.OpConstString, n.Type, n.Val().U)
-		case CTBOOL:
-			v := s.constBool(n.Val().U.(bool))
+			return s.entryNewValue0A(ssa.OpConstString, n.Type, u)
+		case bool:
+			v := s.constBool(u)
 			// For some reason the frontend gets the line numbers of
 			// CTBOOL literals totally wrong. Fix it here by grabbing
 			// the line number of the enclosing AST node.
@@ -1478,7 +1478,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 				v.Line = s.line[len(s.line)-2]
 			}
 			return v
-		case CTNIL:
+		case *NilVal:
 			t := n.Type
 			switch {
 			case t.IsSlice():
@@ -1488,36 +1488,30 @@ func (s *state) expr(n *Node) *ssa.Value {
 			default:
 				return s.constNil(t)
 			}
-		case CTFLT:
-			f := n.Val().U.(*Mpflt)
+		case *Mpflt:
 			switch n.Type.Size() {
 			case 4:
-				return s.constFloat32(n.Type, f.Float32())
+				return s.constFloat32(n.Type, u.Float32())
 			case 8:
-				return s.constFloat64(n.Type, f.Float64())
+				return s.constFloat64(n.Type, u.Float64())
 			default:
 				s.Fatalf("bad float size %d", n.Type.Size())
 				return nil
 			}
-		case CTCPLX:
-			c := n.Val().U.(*Mpcplx)
-			r := &c.Real
-			i := &c.Imag
+		case *Mpcplx:
+			r := &u.Real
+			i := &u.Imag
 			switch n.Type.Size() {
 			case 8:
-				{
-					pt := Types[TFLOAT32]
-					return s.newValue2(ssa.OpComplexMake, n.Type,
-						s.constFloat32(pt, r.Float32()),
-						s.constFloat32(pt, i.Float32()))
-				}
+				pt := Types[TFLOAT32]
+				return s.newValue2(ssa.OpComplexMake, n.Type,
+					s.constFloat32(pt, r.Float32()),
+					s.constFloat32(pt, i.Float32()))
 			case 16:
-				{
-					pt := Types[TFLOAT64]
-					return s.newValue2(ssa.OpComplexMake, n.Type,
-						s.constFloat64(pt, r.Float64()),
-						s.constFloat64(pt, i.Float64()))
-				}
+				pt := Types[TFLOAT64]
+				return s.newValue2(ssa.OpComplexMake, n.Type,
+					s.constFloat64(pt, r.Float64()),
+					s.constFloat64(pt, i.Float64()))
 			default:
 				s.Fatalf("bad float size %d", n.Type.Size())
 				return nil