diff --git a/src/cmd/5g/cgen64.go b/src/cmd/5g/cgen64.go
index 699e555..c55e000 100644
--- a/src/cmd/5g/cgen64.go
+++ b/src/cmd/5g/cgen64.go
@@ -237,7 +237,7 @@
 	//	shld hi:lo, c
 	//	shld lo:t, c
 	case gc.OLROT:
-		v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+		v := uint64(r.Int())
 
 		var bl gc.Node
 		gc.Regalloc(&bl, lo1.Type, nil)
@@ -291,7 +291,7 @@
 		var p4 *obj.Prog
 		var p5 *obj.Prog
 		if r.Op == gc.OLITERAL {
-			v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+			v := uint64(r.Int())
 			if v >= 64 {
 				// TODO(kaib): replace with gins(AMOVW, nodintconst(0), &al)
 				// here and below (verify it optimizes to EOR)
@@ -452,7 +452,7 @@
 		var creg gc.Node
 		var p3 *obj.Prog
 		if r.Op == gc.OLITERAL {
-			v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+			v := uint64(r.Int())
 			if v >= 64 {
 				if bh.Type.Etype == gc.TINT32 {
 					//	MOVW	bh->31, al
diff --git a/src/cmd/5g/ggen.go b/src/cmd/5g/ggen.go
index c2bd6dd..e461236 100644
--- a/src/cmd/5g/ggen.go
+++ b/src/cmd/5g/ggen.go
@@ -183,7 +183,7 @@
 	w := int(nl.Type.Width * 8)
 
 	if op == gc.OLROT {
-		v := int(gc.Mpgetfix(nr.Val.U.Xval))
+		v := nr.Int()
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		if w == 32 {
@@ -210,7 +210,7 @@
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		gc.Cgen(nl, &n1)
-		sc := uint64(gc.Mpgetfix(nr.Val.U.Xval))
+		sc := uint64(nr.Int())
 		if sc == 0 {
 		} else // nothing to do
 		if sc >= uint64(nl.Type.Width*8) {
@@ -480,7 +480,7 @@
 }
 
 func ginscmp(op int, t *gc.Type, n1, n2 *gc.Node, likely int) *obj.Prog {
-	if gc.Isint[t.Etype] && n1.Op == gc.OLITERAL && gc.Mpgetfix(n1.Val.U.Xval) == 0 && n2.Op != gc.OLITERAL {
+	if gc.Isint[t.Etype] && n1.Op == gc.OLITERAL && n1.Int() == 0 && n2.Op != gc.OLITERAL {
 		op = gc.Brrev(op)
 		n1, n2 = n2, n1
 	}
@@ -489,7 +489,7 @@
 	gc.Regalloc(&g1, n1.Type, &r1)
 	gc.Cgen(n1, &g1)
 	gmove(&g1, &r1)
-	if gc.Isint[t.Etype] && n2.Op == gc.OLITERAL && gc.Mpgetfix(n2.Val.U.Xval) == 0 {
+	if gc.Isint[t.Etype] && n2.Op == gc.OLITERAL && n2.Int() == 0 {
 		gins(arm.ACMP, &r1, n2)
 	} else {
 		gc.Regalloc(&r2, t, n2)
diff --git a/src/cmd/5g/gsubr.go b/src/cmd/5g/gsubr.go
index 57d511e..db46d6e 100644
--- a/src/cmd/5g/gsubr.go
+++ b/src/cmd/5g/gsubr.go
@@ -53,7 +53,7 @@
 	if ncon_n.Type == nil {
 		gc.Nodconst(&ncon_n, gc.Types[gc.TUINT32], 0)
 	}
-	gc.Mpmovecfix(ncon_n.Val.U.Xval, int64(i))
+	ncon_n.SetInt(int64(i))
 	return &ncon_n
 }
 
@@ -112,7 +112,7 @@
 	case gc.OLITERAL:
 		var n1 gc.Node
 		gc.Convconst(&n1, n.Type, &n.Val)
-		i := gc.Mpgetfix(n1.Val.U.Xval)
+		i := n1.Int()
 		gc.Nodconst(lo, gc.Types[gc.TUINT32], int64(uint32(i)))
 		i >>= 32
 		if n.Type.Etype == gc.TINT64 {
@@ -1118,7 +1118,7 @@
 		if !gc.Isconst(n, gc.CTINT) {
 			break
 		}
-		v := gc.Mpgetfix(n.Val.U.Xval)
+		v := n.Int()
 		if v >= 32000 || v <= -32000 {
 			break
 		}
diff --git a/src/cmd/6g/ggen.go b/src/cmd/6g/ggen.go
index 6e5e6bc..12198d7 100644
--- a/src/cmd/6g/ggen.go
+++ b/src/cmd/6g/ggen.go
@@ -190,9 +190,9 @@
 	check := 0
 	if gc.Issigned[t.Etype] {
 		check = 1
-		if gc.Isconst(nl, gc.CTINT) && gc.Mpgetfix(nl.Val.U.Xval) != -(1<<uint64(t.Width*8-1)) {
+		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -(1<<uint64(t.Width*8-1)) {
 			check = 0
-		} else if gc.Isconst(nr, gc.CTINT) && gc.Mpgetfix(nr.Val.U.Xval) != -1 {
+		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
 			check = 0
 		}
 	}
@@ -381,7 +381,7 @@
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		gc.Cgen(nl, &n1)
-		sc := uint64(gc.Mpgetfix(nr.Val.U.Xval))
+		sc := uint64(nr.Int())
 		if sc >= uint64(nl.Type.Width*8) {
 			// large shift gets 2 shifts by width-1
 			var n3 gc.Node
diff --git a/src/cmd/6g/gsubr.go b/src/cmd/6g/gsubr.go
index 14e1a57..4e54bc8 100644
--- a/src/cmd/6g/gsubr.go
+++ b/src/cmd/6g/gsubr.go
@@ -32,6 +32,7 @@
 
 import (
 	"cmd/internal/gc"
+	"cmd/internal/gc/big"
 	"cmd/internal/obj"
 	"cmd/internal/obj/x86"
 	"fmt"
@@ -139,29 +140,27 @@
 	gins(jmptoset(a), nil, n)
 }
 
-/*
- * set up nodes representing 2^63
- */
-var bigi gc.Node
-
-var bigf gc.Node
-
-var bignodes_did int
+// set up nodes representing 2^63
+var (
+	bigi         gc.Node
+	bigf         gc.Node
+	bignodes_did bool
+)
 
 func bignodes() {
-	if bignodes_did != 0 {
+	if bignodes_did {
 		return
 	}
-	bignodes_did = 1
+	bignodes_did = true
 
-	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 1)
-	gc.Mpshiftfix(bigi.Val.U.Xval, 63)
+	var i big.Int
+	i.SetInt64(1)
+	i.Lsh(&i, 63)
 
-	bigf = bigi
-	bigf.Type = gc.Types[gc.TFLOAT64]
-	bigf.Val.Ctype = gc.CTFLT
-	bigf.Val.U.Fval = new(gc.Mpflt)
-	gc.Mpmovefixflt(bigf.Val.U.Fval, bigi.Val.U.Xval)
+	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
+	bigi.SetBigInt(&i)
+
+	gc.Convconst(&bigf, gc.Types[gc.TFLOAT64], &bigi.Val)
 }
 
 /*
@@ -206,10 +205,7 @@
 			// 64-bit immediates are really 32-bit sign-extended
 			// unless moving into a register.
 			if gc.Isint[tt] {
-				if gc.Mpcmpfixfix(con.Val.U.Xval, gc.Minintval[gc.TINT32]) < 0 {
-					goto hard
-				}
-				if gc.Mpcmpfixfix(con.Val.U.Xval, gc.Maxintval[gc.TINT32]) > 0 {
+				if i := con.Int(); int64(int32(i)) != i {
 					goto hard
 				}
 			}
@@ -1273,7 +1269,7 @@
 		if !gc.Isconst(n, gc.CTINT) {
 			break
 		}
-		v := gc.Mpgetfix(n.Val.U.Xval)
+		v := n.Int()
 		if v >= 32000 || v <= -32000 {
 			break
 		}
diff --git a/src/cmd/7g/ggen.go b/src/cmd/7g/ggen.go
index b824a3a..af51c31 100644
--- a/src/cmd/7g/ggen.go
+++ b/src/cmd/7g/ggen.go
@@ -147,9 +147,9 @@
 	check := 0
 	if gc.Issigned[t.Etype] {
 		check = 1
-		if gc.Isconst(nl, gc.CTINT) && gc.Mpgetfix(nl.Val.U.Xval) != -(1<<uint64(t.Width*8-1)) {
+		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -(1<<uint64(t.Width*8-1)) {
 			check = 0
-		} else if gc.Isconst(nr, gc.CTINT) && gc.Mpgetfix(nr.Val.U.Xval) != -1 {
+		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
 			check = 0
 		}
 	}
@@ -312,7 +312,7 @@
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		gc.Cgen(nl, &n1)
-		sc := uint64(uint64(gc.Mpgetfix(nr.Val.U.Xval)))
+		sc := uint64(nr.Int())
 		if sc >= uint64(nl.Type.Width*8) {
 			// large shift gets 2 shifts by width-1
 			var n3 gc.Node
diff --git a/src/cmd/7g/gsubr.go b/src/cmd/7g/gsubr.go
index 60c3a7a..2f03b12 100644
--- a/src/cmd/7g/gsubr.go
+++ b/src/cmd/7g/gsubr.go
@@ -115,7 +115,7 @@
 	gc.Cgen(n1, &g1)
 	gmove(&g1, &r1)
 	if gc.Isint[t.Etype] && gc.Isconst(n2, gc.CTINT) {
-		ginscon2(optoas(gc.OCMP, t), &r1, gc.Mpgetfix(n2.Val.U.Xval))
+		ginscon2(optoas(gc.OCMP, t), &r1, n2.Int())
 	} else {
 		gc.Regalloc(&r2, t, n2)
 		gc.Regalloc(&g2, n1.Type, &r2)
@@ -473,7 +473,7 @@
 	}
 	switch n.Val.Ctype {
 	case gc.CTINT, gc.CTRUNE:
-		return gc.Mpgetfix(n.Val.U.Xval), true
+		return n.Int(), true
 	case gc.CTBOOL:
 		return int64(obj.Bool2int(n.Val.U.Bval)), true
 	}
diff --git a/src/cmd/8g/cgen64.go b/src/cmd/8g/cgen64.go
index a682e2f..80a9642 100644
--- a/src/cmd/8g/cgen64.go
+++ b/src/cmd/8g/cgen64.go
@@ -162,7 +162,7 @@
 	//	shld hi:lo, c
 	//	shld lo:t, c
 	case gc.OLROT:
-		v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+		v := uint64(r.Int())
 
 		if v >= 32 {
 			// reverse during load to do the first 32 bits of rotate
@@ -189,7 +189,7 @@
 
 	case gc.OLSH:
 		if r.Op == gc.OLITERAL {
-			v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+			v := uint64(r.Int())
 			if v >= 64 {
 				if gc.Is64(r.Type) {
 					splitclean()
@@ -278,7 +278,7 @@
 
 	case gc.ORSH:
 		if r.Op == gc.OLITERAL {
-			v := uint64(gc.Mpgetfix(r.Val.U.Xval))
+			v := uint64(r.Int())
 			if v >= 64 {
 				if gc.Is64(r.Type) {
 					splitclean()
@@ -400,9 +400,8 @@
 
 		if lo2.Op == gc.OLITERAL {
 			// special cases for constants.
-			lv := uint32(gc.Mpgetfix(lo2.Val.U.Xval))
-
-			hv := uint32(gc.Mpgetfix(hi2.Val.U.Xval))
+			lv := uint32(lo2.Int())
+			hv := uint32(hi2.Int())
 			splitclean() // right side
 			split64(res, &lo2, &hi2)
 			switch n.Op {
diff --git a/src/cmd/8g/ggen.go b/src/cmd/8g/ggen.go
index 5902552..baa1b64 100644
--- a/src/cmd/8g/ggen.go
+++ b/src/cmd/8g/ggen.go
@@ -216,9 +216,9 @@
 	check := 0
 	if gc.Issigned[t.Etype] {
 		check = 1
-		if gc.Isconst(nl, gc.CTINT) && gc.Mpgetfix(nl.Val.U.Xval) != -1<<uint64(t.Width*8-1) {
+		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -1<<uint64(t.Width*8-1) {
 			check = 0
-		} else if gc.Isconst(nr, gc.CTINT) && gc.Mpgetfix(nr.Val.U.Xval) != -1 {
+		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
 			check = 0
 		}
 	}
@@ -391,7 +391,7 @@
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		gmove(&n2, &n1)
-		sc := uint64(gc.Mpgetfix(nr.Val.U.Xval))
+		sc := uint64(nr.Int())
 		if sc >= uint64(nl.Type.Width*8) {
 			// large shift gets 2 shifts by width-1
 			gins(a, ncon(uint32(w)-1), &n1)
diff --git a/src/cmd/8g/gsubr.go b/src/cmd/8g/gsubr.go
index d1134d2..6878883 100644
--- a/src/cmd/8g/gsubr.go
+++ b/src/cmd/8g/gsubr.go
@@ -32,6 +32,7 @@
 
 import (
 	"cmd/internal/gc"
+	"cmd/internal/gc/big"
 	"cmd/internal/obj"
 	"cmd/internal/obj/x86"
 	"fmt"
@@ -641,7 +642,7 @@
 	if ncon_n.Type == nil {
 		gc.Nodconst(&ncon_n, gc.Types[gc.TUINT32], 0)
 	}
-	gc.Mpmovecfix(ncon_n.Val.U.Xval, int64(i))
+	ncon_n.SetInt(int64(i))
 	return &ncon_n
 }
 
@@ -700,7 +701,7 @@
 	case gc.OLITERAL:
 		var n1 gc.Node
 		gc.Convconst(&n1, n.Type, &n.Val)
-		i := gc.Mpgetfix(n1.Val.U.Xval)
+		i := n1.Int()
 		gc.Nodconst(lo, gc.Types[gc.TUINT32], int64(uint32(i)))
 		i >>= 32
 		if n.Type.Etype == gc.TINT64 {
@@ -721,36 +722,36 @@
 	}
 }
 
-/*
- * set up nodes representing fp constants
- */
-var zerof gc.Node
-
-var two64f gc.Node
-
-var two63f gc.Node
-
-var bignodes_did int
+// set up nodes representing fp constants
+var (
+	zerof        gc.Node
+	two63f       gc.Node
+	two64f       gc.Node
+	bignodes_did bool
+)
 
 func bignodes() {
-	if bignodes_did != 0 {
+	if bignodes_did {
 		return
 	}
-	bignodes_did = 1
+	bignodes_did = true
 
-	two64f = *ncon(0)
-	two64f.Type = gc.Types[gc.TFLOAT64]
-	two64f.Val.Ctype = gc.CTFLT
-	two64f.Val.U.Fval = new(gc.Mpflt)
-	gc.Mpmovecflt(two64f.Val.U.Fval, 18446744073709551616.)
+	gc.Nodconst(&zerof, gc.Types[gc.TINT64], 0)
+	gc.Convconst(&zerof, gc.Types[gc.TFLOAT64], &zerof.Val)
 
-	two63f = two64f
-	two63f.Val.U.Fval = new(gc.Mpflt)
-	gc.Mpmovecflt(two63f.Val.U.Fval, 9223372036854775808.)
+	var i big.Int
+	i.SetInt64(1)
+	i.Lsh(&i, 63)
+	var bigi gc.Node
 
-	zerof = two64f
-	zerof.Val.U.Fval = new(gc.Mpflt)
-	gc.Mpmovecflt(zerof.Val.U.Fval, 0)
+	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
+	bigi.SetBigInt(&i)
+	gc.Convconst(&two63f, gc.Types[gc.TFLOAT64], &bigi.Val)
+
+	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
+	i.Lsh(&i, 1)
+	bigi.SetBigInt(&i)
+	gc.Convconst(&two64f, gc.Types[gc.TFLOAT64], &bigi.Val)
 }
 
 func memname(n *gc.Node, t *gc.Type) {
diff --git a/src/cmd/9g/ggen.go b/src/cmd/9g/ggen.go
index 28ebd9c..2655369 100644
--- a/src/cmd/9g/ggen.go
+++ b/src/cmd/9g/ggen.go
@@ -141,9 +141,9 @@
 	check := 0
 	if gc.Issigned[t.Etype] {
 		check = 1
-		if gc.Isconst(nl, gc.CTINT) && gc.Mpgetfix(nl.Val.U.Xval) != -(1<<uint64(t.Width*8-1)) {
+		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -(1<<uint64(t.Width*8-1)) {
 			check = 0
-		} else if gc.Isconst(nr, gc.CTINT) && gc.Mpgetfix(nr.Val.U.Xval) != -1 {
+		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
 			check = 0
 		}
 	}
@@ -308,7 +308,7 @@
 		var n1 gc.Node
 		gc.Regalloc(&n1, nl.Type, res)
 		gc.Cgen(nl, &n1)
-		sc := uint64(uint64(gc.Mpgetfix(nr.Val.U.Xval)))
+		sc := uint64(nr.Int())
 		if sc >= uint64(nl.Type.Width*8) {
 			// large shift gets 2 shifts by width-1
 			var n3 gc.Node
diff --git a/src/cmd/9g/gsubr.go b/src/cmd/9g/gsubr.go
index 61ba87e..f14f937 100644
--- a/src/cmd/9g/gsubr.go
+++ b/src/cmd/9g/gsubr.go
@@ -32,6 +32,7 @@
 
 import (
 	"cmd/internal/gc"
+	"cmd/internal/gc/big"
 	"cmd/internal/obj"
 	"cmd/internal/obj/ppc64"
 	"fmt"
@@ -129,7 +130,7 @@
 	gc.Cgen(n1, &g1)
 	gmove(&g1, &r1)
 	if gc.Isint[t.Etype] && gc.Isconst(n2, gc.CTINT) {
-		ginscon2(optoas(gc.OCMP, t), &r1, gc.Mpgetfix(n2.Val.U.Xval))
+		ginscon2(optoas(gc.OCMP, t), &r1, n2.Int())
 	} else {
 		gc.Regalloc(&r2, t, n2)
 		gc.Regalloc(&g2, n1.Type, &r2)
@@ -144,29 +145,27 @@
 	return gc.Gbranch(optoas(op, t), nil, likely)
 }
 
-/*
- * set up nodes representing 2^63
- */
-var bigi gc.Node
-
-var bigf gc.Node
-
-var bignodes_did int
+// set up nodes representing 2^63
+var (
+	bigi         gc.Node
+	bigf         gc.Node
+	bignodes_did bool
+)
 
 func bignodes() {
-	if bignodes_did != 0 {
+	if bignodes_did {
 		return
 	}
-	bignodes_did = 1
+	bignodes_did = true
 
-	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 1)
-	gc.Mpshiftfix(bigi.Val.U.Xval, 63)
+	var i big.Int
+	i.SetInt64(1)
+	i.Lsh(&i, 63)
 
-	bigf = bigi
-	bigf.Type = gc.Types[gc.TFLOAT64]
-	bigf.Val.Ctype = gc.CTFLT
-	bigf.Val.U.Fval = new(gc.Mpflt)
-	gc.Mpmovefixflt(bigf.Val.U.Fval, bigi.Val.U.Xval)
+	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
+	bigi.SetBigInt(&i)
+
+	gc.Convconst(&bigf, gc.Types[gc.TFLOAT64], &bigi.Val)
 }
 
 /*
@@ -552,7 +551,7 @@
 	}
 	switch n.Val.Ctype {
 	case gc.CTINT, gc.CTRUNE:
-		return gc.Mpgetfix(n.Val.U.Xval), true
+		return n.Int(), true
 	case gc.CTBOOL:
 		return int64(obj.Bool2int(n.Val.U.Bval)), true
 	}
diff --git a/src/cmd/internal/gc/const.go b/src/cmd/internal/gc/const.go
index 84b1337..7487526 100644
--- a/src/cmd/internal/gc/const.go
+++ b/src/cmd/internal/gc/const.go
@@ -5,10 +5,38 @@
 package gc
 
 import (
+	"cmd/internal/gc/big"
 	"cmd/internal/obj"
 	"strings"
 )
 
+// Int returns n as an int.
+// n must be an integer constant.
+func (n *Node) Int() int64 {
+	if !Isconst(n, CTINT) {
+		Fatal("Int(%v)", n)
+	}
+	return Mpgetfix(n.Val.U.Xval)
+}
+
+// SetInt sets n's value to i.
+// n must be an integer constant.
+func (n *Node) SetInt(i int64) {
+	if !Isconst(n, CTINT) {
+		Fatal("SetInt(%v)", n)
+	}
+	Mpmovecfix(n.Val.U.Xval, i)
+}
+
+// SetBigInt sets n's value to x.
+// n must be an integer constant.
+func (n *Node) SetBigInt(x *big.Int) {
+	if !Isconst(n, CTINT) {
+		Fatal("SetBigInt(%v)", n)
+	}
+	n.Val.U.Xval.Val.Set(x)
+}
+
 /*
  * truncate float literal fv to 32-bit or 64-bit precision
  * according to type; return truncated value.