github.com/rsc/go@v0.0.0-20150416155037-e040fd465409/src/cmd/internal/gc/const.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gc

import (
	"cmd/internal/obj"
	"strings"
)

/*
 * truncate float literal fv to 32-bit or 64-bit precision
 * according to type; return truncated value.
 */
func truncfltlit(oldv *Mpflt, t *Type) *Mpflt {
	if t == nil {
		return oldv
	}

	var v Val
	v.Ctype = CTFLT
	v.U.Fval = oldv
	overflow(v, t)

	fv := newMpflt()
	mpmovefltflt(fv, oldv)

	// convert large precision literal floating
	// into limited precision (float64 or float32)
	switch t.Etype {
	case TFLOAT64:
		d := mpgetflt(fv)
		Mpmovecflt(fv, d)

	case TFLOAT32:
		d := mpgetflt32(fv)
		Mpmovecflt(fv, d)
	}

	return fv
}

/*
 * convert n, if literal, to type t.
 * implicit conversion.
 */
func Convlit(np **Node, t *Type) {
	convlit1(np, t, false)
}

/*
 * convert n, if literal, to type t.
 * return a new node if necessary
 * (if n is a named constant, can't edit n->type directly).
 */
func convlit1(np **Node, t *Type, explicit bool) {
	n := *np
	if n == nil || t == nil || n.Type == nil || isideal(t) || n.Type == t {
		return
	}
	if !explicit && !isideal(n.Type) {
		return
	}

	if n.Op == OLITERAL {
		nn := Nod(OXXX, nil, nil)
		*nn = *n
		n = nn
		*np = n
	}

	switch n.Op {
	default:
		if n.Type == idealbool {
			if t.Etype == TBOOL {
				n.Type = t
			} else {
				n.Type = Types[TBOOL]
			}
		}

		if n.Type.Etype == TIDEAL {
			Convlit(&n.Left, t)
			Convlit(&n.Right, t)
			n.Type = t
		}

		return

		// target is invalid type for a constant?  leave alone.
	case OLITERAL:
		if !okforconst[t.Etype] && n.Type.Etype != TNIL {
			defaultlit(&n, nil)
			*np = n
			return
		}

	case OLSH, ORSH:
		convlit1(&n.Left, t, explicit && isideal(n.Left.Type))
		t = n.Left.Type
		if t != nil && t.Etype == TIDEAL && n.Val.Ctype != CTINT {
			n.Val = toint(n.Val)
		}
		if t != nil && !Isint[t.Etype] {
			Yyerror("invalid operation: %v (shift of type %v)", Nconv(n, 0), Tconv(t, 0))
			t = nil
		}

		n.Type = t
		return

	case OCOMPLEX:
		if n.Type.Etype == TIDEAL {
			switch t.Etype {
			// If trying to convert to non-complex type,
			// leave as complex128 and let typechecker complain.
			default:
				t = Types[TCOMPLEX128]
				fallthrough

				//fallthrough
			case TCOMPLEX128:
				n.Type = t

				Convlit(&n.Left, Types[TFLOAT64])
				Convlit(&n.Right, Types[TFLOAT64])

			case TCOMPLEX64:
				n.Type = t
				Convlit(&n.Left, Types[TFLOAT32])
				Convlit(&n.Right, Types[TFLOAT32])
			}
		}

		return
	}

	// avoided repeated calculations, errors
	if Eqtype(n.Type, t) {
		return
	}

	ct := consttype(n)
	var et int
	if ct < 0 {
		goto bad
	}

	et = int(t.Etype)
	if et == TINTER {
		if ct == CTNIL && n.Type == Types[TNIL] {
			n.Type = t
			return
		}

		defaultlit(np, nil)
		return
	}

	switch ct {
	default:
		goto bad

	case CTNIL:
		switch et {
		default:
			n.Type = nil
			goto bad

			// let normal conversion code handle it
		case TSTRING:
			return

		case TARRAY:
			if !Isslice(t) {
				goto bad
			}

		case TPTR32,
			TPTR64,
			TINTER,
			TMAP,
			TCHAN,
			TFUNC,
			TUNSAFEPTR:
			break

			// A nil literal may be converted to uintptr
		// if it is an unsafe.Pointer
		case TUINTPTR:
			if n.Type.Etype == TUNSAFEPTR {
				n.Val.U.Xval = new(Mpint)
				Mpmovecfix(n.Val.U.Xval, 0)
				n.Val.Ctype = CTINT
			} else {
				goto bad
			}
		}

	case CTSTR, CTBOOL:
		if et != int(n.Type.Etype) {
			goto bad
		}

	case CTINT, CTRUNE, CTFLT, CTCPLX:
		ct := int(n.Val.Ctype)
		if Isint[et] {
			switch ct {
			default:
				goto bad

			case CTCPLX, CTFLT, CTRUNE:
				n.Val = toint(n.Val)
				fallthrough

				// flowthrough
			case CTINT:
				overflow(n.Val, t)
			}
		} else if Isfloat[et] {
			switch ct {
			default:
				goto bad

			case CTCPLX, CTINT, CTRUNE:
				n.Val = toflt(n.Val)
				fallthrough

				// flowthrough
			case CTFLT:
				n.Val.U.Fval = truncfltlit(n.Val.U.Fval, t)
			}
		} else if Iscomplex[et] {
			switch ct {
			default:
				goto bad

			case CTFLT, CTINT, CTRUNE:
				n.Val = tocplx(n.Val)

			case CTCPLX:
				overflow(n.Val, t)
			}
		} else if et == TSTRING && (ct == CTINT || ct == CTRUNE) && explicit {
			n.Val = tostr(n.Val)
		} else {
			goto bad
		}
	}

	n.Type = t
	return

bad:
	if n.Diag == 0 {
		if t.Broke == 0 {
			Yyerror("cannot convert %v to type %v", Nconv(n, 0), Tconv(t, 0))
		}
		n.Diag = 1
	}

	if isideal(n.Type) {
		defaultlit(&n, nil)
		*np = n
	}

	return
}

func copyval(v Val) Val {
	switch v.Ctype {
	case CTINT, CTRUNE:
		i := new(Mpint)
		mpmovefixfix(i, v.U.Xval)
		v.U.Xval = i

	case CTFLT:
		f := newMpflt()
		mpmovefltflt(f, v.U.Fval)
		v.U.Fval = f

	case CTCPLX:
		c := new(Mpcplx)
		mpmovefltflt(&c.Real, &v.U.Cval.Real)
		mpmovefltflt(&c.Imag, &v.U.Cval.Imag)
		v.U.Cval = c
	}

	return v
}

func tocplx(v Val) Val {
	switch v.Ctype {
	case CTINT, CTRUNE:
		c := new(Mpcplx)
		Mpmovefixflt(&c.Real, v.U.Xval)
		Mpmovecflt(&c.Imag, 0.0)
		v.Ctype = CTCPLX
		v.U.Cval = c

	case CTFLT:
		c := new(Mpcplx)
		mpmovefltflt(&c.Real, v.U.Fval)
		Mpmovecflt(&c.Imag, 0.0)
		v.Ctype = CTCPLX
		v.U.Cval = c
	}

	return v
}

func toflt(v Val) Val {
	switch v.Ctype {
	case CTINT, CTRUNE:
		f := newMpflt()
		Mpmovefixflt(f, v.U.Xval)
		v.Ctype = CTFLT
		v.U.Fval = f

	case CTCPLX:
		f := newMpflt()
		mpmovefltflt(f, &v.U.Cval.Real)
		if mpcmpfltc(&v.U.Cval.Imag, 0) != 0 {
			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.Cval.Real, obj.FmtSharp), Fconv(&v.U.Cval.Imag, obj.FmtSharp|obj.FmtSign))
		}
		v.Ctype = CTFLT
		v.U.Fval = f
	}

	return v
}

func toint(v Val) Val {
	switch v.Ctype {
	case CTRUNE:
		v.Ctype = CTINT

	case CTFLT:
		i := new(Mpint)
		if mpmovefltfix(i, v.U.Fval) < 0 {
			Yyerror("constant %v truncated to integer", Fconv(v.U.Fval, obj.FmtSharp))
		}
		v.Ctype = CTINT
		v.U.Xval = i

	case CTCPLX:
		i := new(Mpint)
		if mpmovefltfix(i, &v.U.Cval.Real) < 0 {
			Yyerror("constant %v%vi truncated to integer", Fconv(&v.U.Cval.Real, obj.FmtSharp), Fconv(&v.U.Cval.Imag, obj.FmtSharp|obj.FmtSign))
		}
		if mpcmpfltc(&v.U.Cval.Imag, 0) != 0 {
			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.Cval.Real, obj.FmtSharp), Fconv(&v.U.Cval.Imag, obj.FmtSharp|obj.FmtSign))
		}
		v.Ctype = CTINT
		v.U.Xval = i
	}

	return v
}

func doesoverflow(v Val, t *Type) bool {
	switch v.Ctype {
	case CTINT, CTRUNE:
		if !Isint[t.Etype] {
			Fatal("overflow: %v integer constant", Tconv(t, 0))
		}
		if Mpcmpfixfix(v.U.Xval, Minintval[t.Etype]) < 0 || Mpcmpfixfix(v.U.Xval, Maxintval[t.Etype]) > 0 {
			return true
		}

	case CTFLT:
		if !Isfloat[t.Etype] {
			Fatal("overflow: %v floating-point constant", Tconv(t, 0))
		}
		if mpcmpfltflt(v.U.Fval, minfltval[t.Etype]) <= 0 || mpcmpfltflt(v.U.Fval, maxfltval[t.Etype]) >= 0 {
			return true
		}

	case CTCPLX:
		if !Iscomplex[t.Etype] {
			Fatal("overflow: %v complex constant", Tconv(t, 0))
		}
		if mpcmpfltflt(&v.U.Cval.Real, minfltval[t.Etype]) <= 0 || mpcmpfltflt(&v.U.Cval.Real, maxfltval[t.Etype]) >= 0 || mpcmpfltflt(&v.U.Cval.Imag, minfltval[t.Etype]) <= 0 || mpcmpfltflt(&v.U.Cval.Imag, maxfltval[t.Etype]) >= 0 {
			return true
		}
	}

	return false
}

func overflow(v Val, t *Type) {
	// v has already been converted
	// to appropriate form for t.
	if t == nil || t.Etype == TIDEAL {
		return
	}

	if !doesoverflow(v, t) {
		return
	}

	switch v.Ctype {
	case CTINT, CTRUNE:
		Yyerror("constant %v overflows %v", Bconv(v.U.Xval, 0), Tconv(t, 0))

	case CTFLT:
		Yyerror("constant %v overflows %v", Fconv(v.U.Fval, obj.FmtSharp), Tconv(t, 0))

	case CTCPLX:
		Yyerror("constant %v overflows %v", Fconv(v.U.Fval, obj.FmtSharp), Tconv(t, 0))
	}
}

func tostr(v Val) Val {
	switch v.Ctype {
	case CTINT, CTRUNE:
		if Mpcmpfixfix(v.U.Xval, Minintval[TINT]) < 0 || Mpcmpfixfix(v.U.Xval, Maxintval[TINT]) > 0 {
			Yyerror("overflow in int -> string")
		}
		r := uint(Mpgetfix(v.U.Xval))
		v = Val{}
		v.Ctype = CTSTR
		v.U.Sval = string(r)

	case CTFLT:
		Yyerror("no float -> string")
		fallthrough

	case CTNIL:
		v = Val{}
		v.Ctype = CTSTR
		v.U.Sval = ""
	}

	return v
}

func consttype(n *Node) int {
	if n == nil || n.Op != OLITERAL {
		return -1
	}
	return int(n.Val.Ctype)
}

func Isconst(n *Node, ct int) bool {
	t := consttype(n)

	// If the caller is asking for CTINT, allow CTRUNE too.
	// Makes life easier for back ends.
	return t == ct || (ct == CTINT && t == CTRUNE)
}

func saveorig(n *Node) *Node {
	if n == n.Orig {
		// duplicate node for n->orig.
		n1 := Nod(OLITERAL, nil, nil)

		n.Orig = n1
		*n1 = *n
	}

	return n.Orig
}

/*
 * if n is constant, rewrite as OLITERAL node.
 */
func evconst(n *Node) {
	// pick off just the opcodes that can be
	// constant evaluated.
	switch n.Op {
	default:
		return

	case OADD,
		OAND,
		OANDAND,
		OANDNOT,
		OARRAYBYTESTR,
		OCOM,
		ODIV,
		OEQ,
		OGE,
		OGT,
		OLE,
		OLSH,
		OLT,
		OMINUS,
		OMOD,
		OMUL,
		ONE,
		ONOT,
		OOR,
		OOROR,
		OPLUS,
		ORSH,
		OSUB,
		OXOR:
		break

	case OCONV:
		if n.Type == nil {
			return
		}
		if !okforconst[n.Type.Etype] && n.Type.Etype != TNIL {
			return
		}

		// merge adjacent constants in the argument list.
	case OADDSTR:
		var nr *Node
		var nl *Node
		var l2 *NodeList
		for l1 := n.List; l1 != nil; l1 = l1.Next {
			if Isconst(l1.N, CTSTR) && l1.Next != nil && Isconst(l1.Next.N, CTSTR) {
				// merge from l1 up to but not including l2
				var strs []string
				l2 = l1
				for l2 != nil && Isconst(l2.N, CTSTR) {
					nr = l2.N
					strs = append(strs, nr.Val.U.Sval)
					l2 = l2.Next
				}

				nl = Nod(OXXX, nil, nil)
				*nl = *l1.N
				nl.Orig = nl
				nl.Val.Ctype = CTSTR
				nl.Val.U.Sval = strings.Join(strs, "")
				l1.N = nl
				l1.Next = l2
			}
		}

		// fix list end pointer.
		for l2 := n.List; l2 != nil; l2 = l2.Next {
			n.List.End = l2
		}

		// collapse single-constant list to single constant.
		if count(n.List) == 1 && Isconst(n.List.N, CTSTR) {
			n.Op = OLITERAL
			n.Val = n.List.N.Val
		}

		return
	}

	nl := n.Left
	if nl == nil || nl.Type == nil {
		return
	}
	if consttype(nl) < 0 {
		return
	}
	wl := int(nl.Type.Etype)
	if Isint[wl] || Isfloat[wl] || Iscomplex[wl] {
		wl = TIDEAL
	}

	nr := n.Right
	var rv Val
	var lno int
	var wr int
	var v Val
	var norig *Node
	if nr == nil {
		// copy numeric value to avoid modifying
		// nl, in case someone still refers to it (e.g. iota).
		v = nl.Val

		if wl == TIDEAL {
			v = copyval(v)
		}

		switch uint32(n.Op)<<16 | uint32(v.Ctype) {
		default:
			if n.Diag == 0 {
				Yyerror("illegal constant expression %v %v", Oconv(int(n.Op), 0), Tconv(nl.Type, 0))
				n.Diag = 1
			}

			return

		case OCONV<<16 | CTNIL,
			OARRAYBYTESTR<<16 | CTNIL:
			if n.Type.Etype == TSTRING {
				v = tostr(v)
				nl.Type = n.Type
				break
			}
			fallthrough

			// fall through
		case OCONV<<16 | CTINT,
			OCONV<<16 | CTRUNE,
			OCONV<<16 | CTFLT,
			OCONV<<16 | CTSTR:
			convlit1(&nl, n.Type, true)

			v = nl.Val

		case OPLUS<<16 | CTINT,
			OPLUS<<16 | CTRUNE:
			break

		case OMINUS<<16 | CTINT,
			OMINUS<<16 | CTRUNE:
			mpnegfix(v.U.Xval)

		case OCOM<<16 | CTINT,
			OCOM<<16 | CTRUNE:
			et := Txxx
			if nl.Type != nil {
				et = int(nl.Type.Etype)
			}

			// calculate the mask in b
			// result will be (a ^ mask)
			var b Mpint
			switch et {
			// signed guys change sign
			default:
				Mpmovecfix(&b, -1)

				// unsigned guys invert their bits
			case TUINT8,
				TUINT16,
				TUINT32,
				TUINT64,
				TUINT,
				TUINTPTR:
				mpmovefixfix(&b, Maxintval[et])
			}

			mpxorfixfix(v.U.Xval, &b)

		case OPLUS<<16 | CTFLT:
			break

		case OMINUS<<16 | CTFLT:
			mpnegflt(v.U.Fval)

		case OPLUS<<16 | CTCPLX:
			break

		case OMINUS<<16 | CTCPLX:
			mpnegflt(&v.U.Cval.Real)
			mpnegflt(&v.U.Cval.Imag)

		case ONOT<<16 | CTBOOL:
			if !v.U.Bval {
				goto settrue
			}
			goto setfalse
		}
		goto ret
	}
	if nr.Type == nil {
		return
	}
	if consttype(nr) < 0 {
		return
	}
	wr = int(nr.Type.Etype)
	if Isint[wr] || Isfloat[wr] || Iscomplex[wr] {
		wr = TIDEAL
	}

	// check for compatible general types (numeric, string, etc)
	if wl != wr {
		goto illegal
	}

	// check for compatible types.
	switch n.Op {
	// ideal const mixes with anything but otherwise must match.
	default:
		if nl.Type.Etype != TIDEAL {
			defaultlit(&nr, nl.Type)
			n.Right = nr
		}

		if nr.Type.Etype != TIDEAL {
			defaultlit(&nl, nr.Type)
			n.Left = nl
		}

		if nl.Type.Etype != nr.Type.Etype {
			goto illegal
		}

		// right must be unsigned.
	// left can be ideal.
	case OLSH, ORSH:
		defaultlit(&nr, Types[TUINT])

		n.Right = nr
		if nr.Type != nil && (Issigned[nr.Type.Etype] || !Isint[nr.Type.Etype]) {
			goto illegal
		}
		if nl.Val.Ctype != CTRUNE {
			nl.Val = toint(nl.Val)
		}
		nr.Val = toint(nr.Val)
	}

	// copy numeric value to avoid modifying
	// n->left, in case someone still refers to it (e.g. iota).
	v = nl.Val

	if wl == TIDEAL {
		v = copyval(v)
	}

	rv = nr.Val

	// convert to common ideal
	if v.Ctype == CTCPLX || rv.Ctype == CTCPLX {
		v = tocplx(v)
		rv = tocplx(rv)
	}

	if v.Ctype == CTFLT || rv.Ctype == CTFLT {
		v = toflt(v)
		rv = toflt(rv)
	}

	// Rune and int turns into rune.
	if v.Ctype == CTRUNE && rv.Ctype == CTINT {
		rv.Ctype = CTRUNE
	}
	if v.Ctype == CTINT && rv.Ctype == CTRUNE {
		if n.Op == OLSH || n.Op == ORSH {
			rv.Ctype = CTINT
		} else {
			v.Ctype = CTRUNE
		}
	}

	if v.Ctype != rv.Ctype {
		// Use of undefined name as constant?
		if (v.Ctype == 0 || rv.Ctype == 0) && nerrors > 0 {
			return
		}
		Fatal("constant type mismatch %v(%d) %v(%d)", Tconv(nl.Type, 0), v.Ctype, Tconv(nr.Type, 0), rv.Ctype)
	}

	// run op
	switch uint32(n.Op)<<16 | uint32(v.Ctype) {
	default:
		goto illegal

	case OADD<<16 | CTINT,
		OADD<<16 | CTRUNE:
		mpaddfixfix(v.U.Xval, rv.U.Xval, 0)

	case OSUB<<16 | CTINT,
		OSUB<<16 | CTRUNE:
		mpsubfixfix(v.U.Xval, rv.U.Xval)

	case OMUL<<16 | CTINT,
		OMUL<<16 | CTRUNE:
		mpmulfixfix(v.U.Xval, rv.U.Xval)

	case ODIV<<16 | CTINT,
		ODIV<<16 | CTRUNE:
		if mpcmpfixc(rv.U.Xval, 0) == 0 {
			Yyerror("division by zero")
			Mpmovecfix(v.U.Xval, 1)
			break
		}

		mpdivfixfix(v.U.Xval, rv.U.Xval)

	case OMOD<<16 | CTINT,
		OMOD<<16 | CTRUNE:
		if mpcmpfixc(rv.U.Xval, 0) == 0 {
			Yyerror("division by zero")
			Mpmovecfix(v.U.Xval, 1)
			break
		}

		mpmodfixfix(v.U.Xval, rv.U.Xval)

	case OLSH<<16 | CTINT,
		OLSH<<16 | CTRUNE:
		mplshfixfix(v.U.Xval, rv.U.Xval)

	case ORSH<<16 | CTINT,
		ORSH<<16 | CTRUNE:
		mprshfixfix(v.U.Xval, rv.U.Xval)

	case OOR<<16 | CTINT,
		OOR<<16 | CTRUNE:
		mporfixfix(v.U.Xval, rv.U.Xval)

	case OAND<<16 | CTINT,
		OAND<<16 | CTRUNE:
		mpandfixfix(v.U.Xval, rv.U.Xval)

	case OANDNOT<<16 | CTINT,
		OANDNOT<<16 | CTRUNE:
		mpandnotfixfix(v.U.Xval, rv.U.Xval)

	case OXOR<<16 | CTINT,
		OXOR<<16 | CTRUNE:
		mpxorfixfix(v.U.Xval, rv.U.Xval)

	case OADD<<16 | CTFLT:
		mpaddfltflt(v.U.Fval, rv.U.Fval)

	case OSUB<<16 | CTFLT:
		mpsubfltflt(v.U.Fval, rv.U.Fval)

	case OMUL<<16 | CTFLT:
		mpmulfltflt(v.U.Fval, rv.U.Fval)

	case ODIV<<16 | CTFLT:
		if mpcmpfltc(rv.U.Fval, 0) == 0 {
			Yyerror("division by zero")
			Mpmovecflt(v.U.Fval, 1.0)
			break
		}

		mpdivfltflt(v.U.Fval, rv.U.Fval)

		// The default case above would print 'ideal % ideal',
	// which is not quite an ideal error.
	case OMOD<<16 | CTFLT:
		if n.Diag == 0 {
			Yyerror("illegal constant expression: floating-point %% operation")
			n.Diag = 1
		}

		return

	case OADD<<16 | CTCPLX:
		mpaddfltflt(&v.U.Cval.Real, &rv.U.Cval.Real)
		mpaddfltflt(&v.U.Cval.Imag, &rv.U.Cval.Imag)

	case OSUB<<16 | CTCPLX:
		mpsubfltflt(&v.U.Cval.Real, &rv.U.Cval.Real)
		mpsubfltflt(&v.U.Cval.Imag, &rv.U.Cval.Imag)

	case OMUL<<16 | CTCPLX:
		cmplxmpy(v.U.Cval, rv.U.Cval)

	case ODIV<<16 | CTCPLX:
		if mpcmpfltc(&rv.U.Cval.Real, 0) == 0 && mpcmpfltc(&rv.U.Cval.Imag, 0) == 0 {
			Yyerror("complex division by zero")
			Mpmovecflt(&rv.U.Cval.Real, 1.0)
			Mpmovecflt(&rv.U.Cval.Imag, 0.0)
			break
		}

		cmplxdiv(v.U.Cval, rv.U.Cval)

	case OEQ<<16 | CTNIL:
		goto settrue

	case ONE<<16 | CTNIL:
		goto setfalse

	case OEQ<<16 | CTINT,
		OEQ<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) == 0 {
			goto settrue
		}
		goto setfalse

	case ONE<<16 | CTINT,
		ONE<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) != 0 {
			goto settrue
		}
		goto setfalse

	case OLT<<16 | CTINT,
		OLT<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) < 0 {
			goto settrue
		}
		goto setfalse

	case OLE<<16 | CTINT,
		OLE<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) <= 0 {
			goto settrue
		}
		goto setfalse

	case OGE<<16 | CTINT,
		OGE<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) >= 0 {
			goto settrue
		}
		goto setfalse

	case OGT<<16 | CTINT,
		OGT<<16 | CTRUNE:
		if Mpcmpfixfix(v.U.Xval, rv.U.Xval) > 0 {
			goto settrue
		}
		goto setfalse

	case OEQ<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) == 0 {
			goto settrue
		}
		goto setfalse

	case ONE<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) != 0 {
			goto settrue
		}
		goto setfalse

	case OLT<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) < 0 {
			goto settrue
		}
		goto setfalse

	case OLE<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) <= 0 {
			goto settrue
		}
		goto setfalse

	case OGE<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) >= 0 {
			goto settrue
		}
		goto setfalse

	case OGT<<16 | CTFLT:
		if mpcmpfltflt(v.U.Fval, rv.U.Fval) > 0 {
			goto settrue
		}
		goto setfalse

	case OEQ<<16 | CTCPLX:
		if mpcmpfltflt(&v.U.Cval.Real, &rv.U.Cval.Real) == 0 && mpcmpfltflt(&v.U.Cval.Imag, &rv.U.Cval.Imag) == 0 {
			goto settrue
		}
		goto setfalse

	case ONE<<16 | CTCPLX:
		if mpcmpfltflt(&v.U.Cval.Real, &rv.U.Cval.Real) != 0 || mpcmpfltflt(&v.U.Cval.Imag, &rv.U.Cval.Imag) != 0 {
			goto settrue
		}
		goto setfalse

	case OEQ<<16 | CTSTR:
		if cmpslit(nl, nr) == 0 {
			goto settrue
		}
		goto setfalse

	case ONE<<16 | CTSTR:
		if cmpslit(nl, nr) != 0 {
			goto settrue
		}
		goto setfalse

	case OLT<<16 | CTSTR:
		if cmpslit(nl, nr) < 0 {
			goto settrue
		}
		goto setfalse

	case OLE<<16 | CTSTR:
		if cmpslit(nl, nr) <= 0 {
			goto settrue
		}
		goto setfalse

	case OGE<<16 | CTSTR:
		if cmpslit(nl, nr) >= 0 {
			goto settrue
		}
		goto setfalse

	case OGT<<16 | CTSTR:
		if cmpslit(nl, nr) > 0 {
			goto settrue
		}
		goto setfalse

	case OOROR<<16 | CTBOOL:
		if v.U.Bval || rv.U.Bval {
			goto settrue
		}
		goto setfalse

	case OANDAND<<16 | CTBOOL:
		if v.U.Bval && rv.U.Bval {
			goto settrue
		}
		goto setfalse

	case OEQ<<16 | CTBOOL:
		if v.U.Bval == rv.U.Bval {
			goto settrue
		}
		goto setfalse

	case ONE<<16 | CTBOOL:
		if v.U.Bval != rv.U.Bval {
			goto settrue
		}
		goto setfalse
	}

	goto ret

ret:
	norig = saveorig(n)
	*n = *nl

	// restore value of n->orig.
	n.Orig = norig

	n.Val = v

	// check range.
	lno = int(setlineno(n))

	overflow(v, n.Type)
	lineno = int32(lno)

	// truncate precision for non-ideal float.
	if v.Ctype == CTFLT && n.Type.Etype != TIDEAL {
		n.Val.U.Fval = truncfltlit(v.U.Fval, n.Type)
	}
	return

settrue:
	norig = saveorig(n)
	*n = *Nodbool(true)
	n.Orig = norig
	return

setfalse:
	norig = saveorig(n)
	*n = *Nodbool(false)
	n.Orig = norig
	return

illegal:
	if n.Diag == 0 {
		Yyerror("illegal constant expression: %v %v %v", Tconv(nl.Type, 0), Oconv(int(n.Op), 0), Tconv(nr.Type, 0))
		n.Diag = 1
	}

	return
}

func nodlit(v Val) *Node {
	n := Nod(OLITERAL, nil, nil)
	n.Val = v
	switch v.Ctype {
	default:
		Fatal("nodlit ctype %d", v.Ctype)

	case CTSTR:
		n.Type = idealstring

	case CTBOOL:
		n.Type = idealbool

	case CTINT, CTRUNE, CTFLT, CTCPLX:
		n.Type = Types[TIDEAL]

	case CTNIL:
		n.Type = Types[TNIL]
	}

	return n
}

func nodcplxlit(r Val, i Val) *Node {
	r = toflt(r)
	i = toflt(i)

	c := new(Mpcplx)
	n := Nod(OLITERAL, nil, nil)
	n.Type = Types[TIDEAL]
	n.Val.U.Cval = c
	n.Val.Ctype = CTCPLX

	if r.Ctype != CTFLT || i.Ctype != CTFLT {
		Fatal("nodcplxlit ctype %d/%d", r.Ctype, i.Ctype)
	}

	mpmovefltflt(&c.Real, r.U.Fval)
	mpmovefltflt(&c.Imag, i.U.Fval)
	return n
}

// idealkind returns a constant kind like consttype
// but for an arbitrary "ideal" (untyped constant) expression.
func idealkind(n *Node) int {
	if n == nil || !isideal(n.Type) {
		return CTxxx
	}

	switch n.Op {
	default:
		return CTxxx

	case OLITERAL:
		return int(n.Val.Ctype)

		// numeric kinds.
	case OADD,
		OAND,
		OANDNOT,
		OCOM,
		ODIV,
		OMINUS,
		OMOD,
		OMUL,
		OSUB,
		OXOR,
		OOR,
		OPLUS:
		k1 := idealkind(n.Left)

		k2 := idealkind(n.Right)
		if k1 > k2 {
			return k1
		} else {
			return k2
		}
		fallthrough

	case OREAL, OIMAG:
		return CTFLT

	case OCOMPLEX:
		return CTCPLX

	case OADDSTR:
		return CTSTR

	case OANDAND,
		OEQ,
		OGE,
		OGT,
		OLE,
		OLT,
		ONE,
		ONOT,
		OOROR,
		OCMPSTR,
		OCMPIFACE:
		return CTBOOL

		// shifts (beware!).
	case OLSH, ORSH:
		return idealkind(n.Left)
	}
}

func defaultlit(np **Node, t *Type) {
	n := *np
	if n == nil || !isideal(n.Type) {
		return
	}

	if n.Op == OLITERAL {
		nn := Nod(OXXX, nil, nil)
		*nn = *n
		n = nn
		*np = n
	}

	lno := int(setlineno(n))
	ctype := idealkind(n)
	var t1 *Type
	switch ctype {
	default:
		if t != nil {
			Convlit(np, t)
			return
		}

		if n.Val.Ctype == CTNIL {
			lineno = int32(lno)
			if n.Diag == 0 {
				Yyerror("use of untyped nil")
				n.Diag = 1
			}

			n.Type = nil
			break
		}

		if n.Val.Ctype == CTSTR {
			t1 := Types[TSTRING]
			Convlit(np, t1)
			break
		}

		Yyerror("defaultlit: unknown literal: %v", Nconv(n, 0))

	case CTxxx:
		Fatal("defaultlit: idealkind is CTxxx: %v", Nconv(n, obj.FmtSign))

	case CTBOOL:
		t1 := Types[TBOOL]
		if t != nil && t.Etype == TBOOL {
			t1 = t
		}
		Convlit(np, t1)

	case CTINT:
		t1 = Types[TINT]
		goto num

	case CTRUNE:
		t1 = runetype
		goto num

	case CTFLT:
		t1 = Types[TFLOAT64]
		goto num

	case CTCPLX:
		t1 = Types[TCOMPLEX128]
		goto num
	}

	lineno = int32(lno)
	return

num:
	if t != nil {
		if Isint[t.Etype] {
			t1 = t
			n.Val = toint(n.Val)
		} else if Isfloat[t.Etype] {
			t1 = t
			n.Val = toflt(n.Val)
		} else if Iscomplex[t.Etype] {
			t1 = t
			n.Val = tocplx(n.Val)
		}
	}

	overflow(n.Val, t1)
	Convlit(np, t1)
	lineno = int32(lno)
	return
}

/*
 * defaultlit on both nodes simultaneously;
 * if they're both ideal going in they better
 * get the same type going out.
 * force means must assign concrete (non-ideal) type.
 */
func defaultlit2(lp **Node, rp **Node, force int) {
	l := *lp
	r := *rp
	if l.Type == nil || r.Type == nil {
		return
	}
	if !isideal(l.Type) {
		Convlit(rp, l.Type)
		return
	}

	if !isideal(r.Type) {
		Convlit(lp, r.Type)
		return
	}

	if force == 0 {
		return
	}
	if l.Type.Etype == TBOOL {
		Convlit(lp, Types[TBOOL])
		Convlit(rp, Types[TBOOL])
	}

	lkind := idealkind(l)
	rkind := idealkind(r)
	if lkind == CTCPLX || rkind == CTCPLX {
		Convlit(lp, Types[TCOMPLEX128])
		Convlit(rp, Types[TCOMPLEX128])
		return
	}

	if lkind == CTFLT || rkind == CTFLT {
		Convlit(lp, Types[TFLOAT64])
		Convlit(rp, Types[TFLOAT64])
		return
	}

	if lkind == CTRUNE || rkind == CTRUNE {
		Convlit(lp, runetype)
		Convlit(rp, runetype)
		return
	}

	Convlit(lp, Types[TINT])
	Convlit(rp, Types[TINT])
}

func cmpslit(l, r *Node) int {
	return stringsCompare(l.Val.U.Sval, r.Val.U.Sval)
}

func Smallintconst(n *Node) bool {
	if n.Op == OLITERAL && Isconst(n, CTINT) && n.Type != nil {
		switch Simtype[n.Type.Etype] {
		case TINT8,
			TUINT8,
			TINT16,
			TUINT16,
			TINT32,
			TUINT32,
			TBOOL,
			TPTR32:
			return true

		case TIDEAL, TINT64, TUINT64, TPTR64:
			if Mpcmpfixfix(n.Val.U.Xval, Minintval[TINT32]) < 0 || Mpcmpfixfix(n.Val.U.Xval, Maxintval[TINT32]) > 0 {
				break
			}
			return true
		}
	}

	return false
}

func nonnegconst(n *Node) int {
	if n.Op == OLITERAL && n.Type != nil {
		switch Simtype[n.Type.Etype] {
		// check negative and 2^31
		case TINT8,
			TUINT8,
			TINT16,
			TUINT16,
			TINT32,
			TUINT32,
			TINT64,
			TUINT64,
			TIDEAL:
			if Mpcmpfixfix(n.Val.U.Xval, Minintval[TUINT32]) < 0 || Mpcmpfixfix(n.Val.U.Xval, Maxintval[TINT32]) > 0 {
				break
			}
			return int(Mpgetfix(n.Val.U.Xval))
		}
	}

	return -1
}

/*
 * convert x to type et and back to int64
 * for sign extension and truncation.
 */
func iconv(x int64, et int) int64 {
	switch et {
	case TINT8:
		x = int64(int8(x))

	case TUINT8:
		x = int64(uint8(x))

	case TINT16:
		x = int64(int16(x))

	case TUINT16:
		x = int64(uint64(x))

	case TINT32:
		x = int64(int32(x))

	case TUINT32:
		x = int64(uint32(x))

	case TINT64, TUINT64:
		break
	}

	return x
}

/*
 * convert constant val to type t; leave in con.
 * for back end.
 */
func Convconst(con *Node, t *Type, val *Val) {
	tt := Simsimtype(t)

	// copy the constant for conversion
	Nodconst(con, Types[TINT8], 0)

	con.Type = t
	con.Val = *val

	if Isint[tt] {
		con.Val.Ctype = CTINT
		con.Val.U.Xval = new(Mpint)
		var i int64
		switch val.Ctype {
		default:
			Fatal("convconst ctype=%d %v", val.Ctype, Tconv(t, obj.FmtLong))

		case CTINT, CTRUNE:
			i = Mpgetfix(val.U.Xval)

		case CTBOOL:
			i = int64(bool2int(val.U.Bval))

		case CTNIL:
			i = 0
		}

		i = iconv(i, tt)
		Mpmovecfix(con.Val.U.Xval, i)
		return
	}

	if Isfloat[tt] {
		con.Val = toflt(con.Val)
		if con.Val.Ctype != CTFLT {
			Fatal("convconst ctype=%d %v", con.Val.Ctype, Tconv(t, 0))
		}
		if tt == TFLOAT32 {
			con.Val.U.Fval = truncfltlit(con.Val.U.Fval, t)
		}
		return
	}

	if Iscomplex[tt] {
		con.Val = tocplx(con.Val)
		if tt == TCOMPLEX64 {
			con.Val.U.Cval.Real = *truncfltlit(&con.Val.U.Cval.Real, Types[TFLOAT32])
			con.Val.U.Cval.Imag = *truncfltlit(&con.Val.U.Cval.Imag, Types[TFLOAT32])
		}

		return
	}

	Fatal("convconst %v constant", Tconv(t, obj.FmtLong))
}

// complex multiply v *= rv
//	(a, b) * (c, d) = (a*c - b*d, b*c + a*d)
func cmplxmpy(v *Mpcplx, rv *Mpcplx) {
	var ac Mpflt
	var bd Mpflt
	var bc Mpflt
	var ad Mpflt

	mpmovefltflt(&ac, &v.Real)
	mpmulfltflt(&ac, &rv.Real) // ac

	mpmovefltflt(&bd, &v.Imag)

	mpmulfltflt(&bd, &rv.Imag) // bd

	mpmovefltflt(&bc, &v.Imag)

	mpmulfltflt(&bc, &rv.Real) // bc

	mpmovefltflt(&ad, &v.Real)

	mpmulfltflt(&ad, &rv.Imag) // ad

	mpmovefltflt(&v.Real, &ac)

	mpsubfltflt(&v.Real, &bd) // ac-bd

	mpmovefltflt(&v.Imag, &bc)

	mpaddfltflt(&v.Imag, &ad) // bc+ad
}

// complex divide v /= rv
//	(a, b) / (c, d) = ((a*c + b*d), (b*c - a*d))/(c*c + d*d)
func cmplxdiv(v *Mpcplx, rv *Mpcplx) {
	var ac Mpflt
	var bd Mpflt
	var bc Mpflt
	var ad Mpflt
	var cc_plus_dd Mpflt

	mpmovefltflt(&cc_plus_dd, &rv.Real)
	mpmulfltflt(&cc_plus_dd, &rv.Real) // cc

	mpmovefltflt(&ac, &rv.Imag)

	mpmulfltflt(&ac, &rv.Imag) // dd

	mpaddfltflt(&cc_plus_dd, &ac) // cc+dd

	mpmovefltflt(&ac, &v.Real)

	mpmulfltflt(&ac, &rv.Real) // ac

	mpmovefltflt(&bd, &v.Imag)

	mpmulfltflt(&bd, &rv.Imag) // bd

	mpmovefltflt(&bc, &v.Imag)

	mpmulfltflt(&bc, &rv.Real) // bc

	mpmovefltflt(&ad, &v.Real)

	mpmulfltflt(&ad, &rv.Imag) // ad

	mpmovefltflt(&v.Real, &ac)

	mpaddfltflt(&v.Real, &bd)         // ac+bd
	mpdivfltflt(&v.Real, &cc_plus_dd) // (ac+bd)/(cc+dd)

	mpmovefltflt(&v.Imag, &bc)

	mpsubfltflt(&v.Imag, &ad)         // bc-ad
	mpdivfltflt(&v.Imag, &cc_plus_dd) // (bc+ad)/(cc+dd)
}

// Is n a Go language constant (as opposed to a compile-time constant)?
// Expressions derived from nil, like string([]byte(nil)), while they
// may be known at compile time, are not Go language constants.
// Only called for expressions known to evaluated to compile-time
// constants.
func isgoconst(n *Node) bool {
	if n.Orig != nil {
		n = n.Orig
	}

	switch n.Op {
	case OADD,
		OADDSTR,
		OAND,
		OANDAND,
		OANDNOT,
		OCOM,
		ODIV,
		OEQ,
		OGE,
		OGT,
		OLE,
		OLSH,
		OLT,
		OMINUS,
		OMOD,
		OMUL,
		ONE,
		ONOT,
		OOR,
		OOROR,
		OPLUS,
		ORSH,
		OSUB,
		OXOR,
		OIOTA,
		OCOMPLEX,
		OREAL,
		OIMAG:
		if isgoconst(n.Left) && (n.Right == nil || isgoconst(n.Right)) {
			return true
		}

	case OCONV:
		if okforconst[n.Type.Etype] && isgoconst(n.Left) {
			return true
		}

	case OLEN, OCAP:
		l := n.Left
		if isgoconst(l) {
			return true
		}

		// Special case: len/cap is constant when applied to array or
		// pointer to array when the expression does not contain
		// function calls or channel receive operations.
		t := l.Type

		if t != nil && Isptr[t.Etype] {
			t = t.Type
		}
		if Isfixedarray(t) && !hascallchan(l) {
			return true
		}

	case OLITERAL:
		if n.Val.Ctype != CTNIL {
			return true
		}

	case ONAME:
		l := n.Sym.Def
		if l != nil && l.Op == OLITERAL && n.Val.Ctype != CTNIL {
			return true
		}

	case ONONAME:
		if n.Sym.Def != nil && n.Sym.Def.Op == OIOTA {
			return true
		}

		// Only constant calls are unsafe.Alignof, Offsetof, and Sizeof.
	case OCALL:
		l := n.Left

		for l.Op == OPAREN {
			l = l.Left
		}
		if l.Op != ONAME || l.Sym.Pkg != unsafepkg {
			break
		}
		if l.Sym.Name == "Alignof" || l.Sym.Name == "Offsetof" || l.Sym.Name == "Sizeof" {
			return true
		}
	}

	//dump("nonconst", n);
	return false
}

func hascallchan(n *Node) bool {
	if n == nil {
		return false
	}
	switch n.Op {
	case OAPPEND,
		OCALL,
		OCALLFUNC,
		OCALLINTER,
		OCALLMETH,
		OCAP,
		OCLOSE,
		OCOMPLEX,
		OCOPY,
		ODELETE,
		OIMAG,
		OLEN,
		OMAKE,
		ONEW,
		OPANIC,
		OPRINT,
		OPRINTN,
		OREAL,
		ORECOVER,
		ORECV:
		return true
	}

	if hascallchan(n.Left) || hascallchan(n.Right) {
		return true
	}

	for l := n.List; l != nil; l = l.Next {
		if hascallchan(l.N) {
			return true
		}
	}
	for l := n.Rlist; l != nil; l = l.Next {
		if hascallchan(l.N) {
			return true
		}
	}

	return false
}