Golang gc.Isconst函數代碼示例

func intLiteral(n *gc.Node) (x int64, ok bool) {
	switch {
	case n == nil:
		return
	case gc.Isconst(n, gc.CTINT):
		return n.Int(), true
	case gc.Isconst(n, gc.CTBOOL):
		return int64(obj.Bool2int(n.Bool())), true
	}
	return
}

func ginscmp(op int, t *gc.Type, n1, n2 *gc.Node, likely int) *obj.Prog {
	if gc.Isint[t.Etype] && n1.Op == gc.OLITERAL && n2.Op != gc.OLITERAL {
		// Reverse comparison to place constant last.
		op = gc.Brrev(op)
		n1, n2 = n2, n1
	}

	var r1, r2, g1, g2 gc.Node
	gc.Regalloc(&r1, t, n1)
	gc.Regalloc(&g1, n1.Type, &r1)
	gc.Cgen(n1, &g1)
	gmove(&g1, &r1)
	if gc.Isint[t.Etype] && gc.Isconst(n2, gc.CTINT) {
		ginscon2(optoas(gc.OCMP, t), &r1, n2.Int())
	} else {
		gc.Regalloc(&r2, t, n2)
		gc.Regalloc(&g2, n1.Type, &r2)
		gc.Cgen(n2, &g2)
		gmove(&g2, &r2)
		gcmp(optoas(gc.OCMP, t), &r1, &r2)
		gc.Regfree(&g2)
		gc.Regfree(&r2)
	}
	gc.Regfree(&g1)
	gc.Regfree(&r1)
	return gc.Gbranch(optoas(op, t), nil, likely)
}

/*
 * generate division.
 * generates one of:
 *	res = nl / nr
 *	res = nl % nr
 * according to op.
 */
func dodiv(op int, nl *gc.Node, nr *gc.Node, res *gc.Node) {
	// Have to be careful about handling
	// most negative int divided by -1 correctly.
	// The hardware will generate undefined result.
	// Also need to explicitly trap on division on zero,
	// the hardware will silently generate undefined result.
	// DIVW will leave unpredicable result in higher 32-bit,
	// so always use DIVD/DIVDU.
	t := nl.Type

	t0 := t
	check := 0
	if gc.Issigned[t.Etype] {
		check = 1
		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -(1<<uint64(t.Width*8-1)) {
			check = 0
		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
			check = 0
		}
	}

	if t.Width < 8 {
		if gc.Issigned[t.Etype] {
			t = gc.Types[gc.TINT64]
		} else {
			t = gc.Types[gc.TUINT64]
		}
		check = 0
	}

	a := optoas(gc.ODIV, t)

	var tl gc.Node
	gc.Regalloc(&tl, t0, nil)
	var tr gc.Node
	gc.Regalloc(&tr, t0, nil)
	if nl.Ullman >= nr.Ullman {
		gc.Cgen(nl, &tl)
		gc.Cgen(nr, &tr)
	} else {
		gc.Cgen(nr, &tr)
		gc.Cgen(nl, &tl)
	}

	if t != t0 {
		// Convert
		tl2 := tl

		tr2 := tr
		tl.Type = t
		tr.Type = t
		gmove(&tl2, &tl)
		gmove(&tr2, &tr)
	}

	// Handle divide-by-zero panic.
	p1 := gins(optoas(gc.OCMP, t), &tr, nil)

	p1.To.Type = obj.TYPE_REG
	p1.To.Reg = ppc64.REGZERO
	p1 = gc.Gbranch(optoas(gc.ONE, t), nil, +1)
	if panicdiv == nil {
		panicdiv = gc.Sysfunc("panicdivide")
	}
	gc.Ginscall(panicdiv, -1)
	gc.Patch(p1, gc.Pc)

	var p2 *obj.Prog
	if check != 0 {
		var nm1 gc.Node
		gc.Nodconst(&nm1, t, -1)
		gins(optoas(gc.OCMP, t), &tr, &nm1)
		p1 := gc.Gbranch(optoas(gc.ONE, t), nil, +1)
		if op == gc.ODIV {
			// a / (-1) is -a.
			gins(optoas(gc.OMINUS, t), nil, &tl)

			gmove(&tl, res)
		} else {
			// a % (-1) is 0.
			var nz gc.Node
			gc.Nodconst(&nz, t, 0)

			gmove(&nz, res)
		}

		p2 = gc.Gbranch(obj.AJMP, nil, 0)
		gc.Patch(p1, gc.Pc)
	}

	p1 = gins(a, &tr, &tl)
	if op == gc.ODIV {
		gc.Regfree(&tr)
//.........這裏部分代碼省略.........

/*
 * generate division.
 * generates one of:
 *	res = nl / nr
 *	res = nl % nr
 * according to op.
 */
func dodiv(op int, nl *gc.Node, nr *gc.Node, res *gc.Node) {
	// Have to be careful about handling
	// most negative int divided by -1 correctly.
	// The hardware will trap.
	// Also the byte divide instruction needs AH,
	// which we otherwise don't have to deal with.
	// Easiest way to avoid for int8, int16: use int32.
	// For int32 and int64, use explicit test.
	// Could use int64 hw for int32.
	t := nl.Type

	t0 := t
	check := 0
	if gc.Issigned[t.Etype] {
		check = 1
		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -(1<<uint64(t.Width*8-1)) {
			check = 0
		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
			check = 0
		}
	}

	if t.Width < 4 {
		if gc.Issigned[t.Etype] {
			t = gc.Types[gc.TINT32]
		} else {
			t = gc.Types[gc.TUINT32]
		}
		check = 0
	}

	a := optoas(op, t)

	var n3 gc.Node
	gc.Regalloc(&n3, t0, nil)
	var ax gc.Node
	var oldax gc.Node
	if nl.Ullman >= nr.Ullman {
		savex(x86.REG_AX, &ax, &oldax, res, t0)
		gc.Cgen(nl, &ax)
		gc.Regalloc(&ax, t0, &ax) // mark ax live during cgen
		gc.Cgen(nr, &n3)
		gc.Regfree(&ax)
	} else {
		gc.Cgen(nr, &n3)
		savex(x86.REG_AX, &ax, &oldax, res, t0)
		gc.Cgen(nl, &ax)
	}

	if t != t0 {
		// Convert
		ax1 := ax

		n31 := n3
		ax.Type = t
		n3.Type = t
		gmove(&ax1, &ax)
		gmove(&n31, &n3)
	}

	var n4 gc.Node
	if gc.Nacl {
		// Native Client does not relay the divide-by-zero trap
		// to the executing program, so we must insert a check
		// for ourselves.
		gc.Nodconst(&n4, t, 0)

		gins(optoas(gc.OCMP, t), &n3, &n4)
		p1 := gc.Gbranch(optoas(gc.ONE, t), nil, +1)
		if panicdiv == nil {
			panicdiv = gc.Sysfunc("panicdivide")
		}
		gc.Ginscall(panicdiv, -1)
		gc.Patch(p1, gc.Pc)
	}

	var p2 *obj.Prog
	if check != 0 {
		gc.Nodconst(&n4, t, -1)
		gins(optoas(gc.OCMP, t), &n3, &n4)
		p1 := gc.Gbranch(optoas(gc.ONE, t), nil, +1)
		if op == gc.ODIV {
			// a / (-1) is -a.
			gins(optoas(gc.OMINUS, t), nil, &ax)

			gmove(&ax, res)
		} else {
			// a % (-1) is 0.
			gc.Nodconst(&n4, t, 0)

			gmove(&n4, res)
		}

//.........這裏部分代碼省略.........

/*
 * generate one instruction:
 *	as f, t
 */
func gins(as int, f *gc.Node, t *gc.Node) *obj.Prog {
	if as == x86.AFMOVF && f != nil && f.Op == gc.OREGISTER && t != nil && t.Op == gc.OREGISTER {
		gc.Fatalf("gins MOVF reg, reg")
	}
	if as == x86.ACVTSD2SS && f != nil && f.Op == gc.OLITERAL {
		gc.Fatalf("gins CVTSD2SS const")
	}
	if as == x86.AMOVSD && t != nil && t.Op == gc.OREGISTER && t.Reg == x86.REG_F0 {
		gc.Fatalf("gins MOVSD into F0")
	}

	if as == x86.AMOVL && f != nil && f.Op == gc.OADDR && f.Left.Op == gc.ONAME && f.Left.Class != gc.PEXTERN && f.Left.Class != gc.PFUNC {
		// Turn MOVL $xxx(FP/SP) into LEAL xxx.
		// These should be equivalent but most of the backend
		// only expects to see LEAL, because that's what we had
		// historically generated. Various hidden assumptions are baked in by now.
		as = x86.ALEAL
		f = f.Left
	}

	switch as {
	case x86.AMOVB,
		x86.AMOVW,
		x86.AMOVL:
		if f != nil && t != nil && samaddr(f, t) {
			return nil
		}

	case x86.ALEAL:
		if f != nil && gc.Isconst(f, gc.CTNIL) {
			gc.Fatalf("gins LEAL nil %v", f.Type)
		}
	}

	p := gc.Prog(as)
	gc.Naddr(&p.From, f)
	gc.Naddr(&p.To, t)

	if gc.Debug['g'] != 0 {
		fmt.Printf("%v\n", p)
	}

	w := 0
	switch as {
	case x86.AMOVB:
		w = 1

	case x86.AMOVW:
		w = 2

	case x86.AMOVL:
		w = 4
	}

	if true && w != 0 && f != nil && (p.From.Width > int64(w) || p.To.Width > int64(w)) {
		gc.Dump("bad width from:", f)
		gc.Dump("bad width to:", t)
		gc.Fatalf("bad width: %v (%d, %d)\n", p, p.From.Width, p.To.Width)
	}

	if p.To.Type == obj.TYPE_ADDR && w > 0 {
		gc.Fatalf("bad use of addr: %v", p)
	}

	return p
}

/*
 * generate division.
 * caller must set:
 *	ax = allocated AX register
 *	dx = allocated DX register
 * generates one of:
 *	res = nl / nr
 *	res = nl % nr
 * according to op.
 */
func dodiv(op gc.Op, nl *gc.Node, nr *gc.Node, res *gc.Node, ax *gc.Node, dx *gc.Node) {
	// Have to be careful about handling
	// most negative int divided by -1 correctly.
	// The hardware will trap.
	// Also the byte divide instruction needs AH,
	// which we otherwise don't have to deal with.
	// Easiest way to avoid for int8, int16: use int32.
	// For int32 and int64, use explicit test.
	// Could use int64 hw for int32.
	t := nl.Type

	t0 := t
	check := false
	if gc.Issigned[t.Etype] {
		check = true
		if gc.Isconst(nl, gc.CTINT) && nl.Int() != -1<<uint64(t.Width*8-1) {
			check = false
		} else if gc.Isconst(nr, gc.CTINT) && nr.Int() != -1 {
			check = false
		}
	}

	if t.Width < 4 {
		if gc.Issigned[t.Etype] {
			t = gc.Types[gc.TINT32]
		} else {
			t = gc.Types[gc.TUINT32]
		}
		check = false
	}

	var t1 gc.Node
	gc.Tempname(&t1, t)
	var t2 gc.Node
	gc.Tempname(&t2, t)
	if t0 != t {
		var t3 gc.Node
		gc.Tempname(&t3, t0)
		var t4 gc.Node
		gc.Tempname(&t4, t0)
		gc.Cgen(nl, &t3)
		gc.Cgen(nr, &t4)

		// Convert.
		gmove(&t3, &t1)

		gmove(&t4, &t2)
	} else {
		gc.Cgen(nl, &t1)
		gc.Cgen(nr, &t2)
	}

	var n1 gc.Node
	if !gc.Samereg(ax, res) && !gc.Samereg(dx, res) {
		gc.Regalloc(&n1, t, res)
	} else {
		gc.Regalloc(&n1, t, nil)
	}
	gmove(&t2, &n1)
	gmove(&t1, ax)
	var p2 *obj.Prog
	var n4 gc.Node
	if gc.Nacl {
		// Native Client does not relay the divide-by-zero trap
		// to the executing program, so we must insert a check
		// for ourselves.
		gc.Nodconst(&n4, t, 0)

		gins(optoas(gc.OCMP, t), &n1, &n4)
		p1 := gc.Gbranch(optoas(gc.ONE, t), nil, +1)
		if panicdiv == nil {
			panicdiv = gc.Sysfunc("panicdivide")
		}
		gc.Ginscall(panicdiv, -1)
		gc.Patch(p1, gc.Pc)
	}

	if check {
		gc.Nodconst(&n4, t, -1)
		gins(optoas(gc.OCMP, t), &n1, &n4)
		p1 := gc.Gbranch(optoas(gc.ONE, t), nil, +1)
		if op == gc.ODIV {
			// a / (-1) is -a.
			gins(optoas(gc.OMINUS, t), nil, ax)

			gmove(ax, res)
		} else {
			// a % (-1) is 0.
			gc.Nodconst(&n4, t, 0)

//.........這裏部分代碼省略.........

/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as int, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			break
		}
		v := n.Int()
		if v >= 32000 || v <= -32000 {
			break
		}
		switch as {
		default:
			return false

		case arm.AADD,
			arm.ASUB,
			arm.AAND,
			arm.AORR,
			arm.AEOR,
			arm.AMOVB,
			arm.AMOVBS,
			arm.AMOVBU,
			arm.AMOVH,
			arm.AMOVHS,
			arm.AMOVHU,
			arm.AMOVW:
			break
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			gc.Naddr(a, &n1)
			return true
		}

		gc.Regalloc(reg, gc.Types[gc.Tptr], nil)
		n1 := *reg
		n1.Op = gc.OINDREG
		if oary[0] >= 0 {
			gc.Agen(nn, reg)
			n1.Xoffset = oary[0]
		} else {
			gc.Cgen(nn, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[0] + 1)
		}

		for i := 1; i < o; i++ {
			if oary[i] >= 0 {
				gc.Fatal("can't happen")
			}
			gins(arm.AMOVW, &n1, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[i] + 1)
		}

//.........這裏部分代碼省略.........

/*
 * generate one instruction:
 *	as f, t
 */
func gins(as int, f *gc.Node, t *gc.Node) *obj.Prog {
	//	Node nod;

	//	if(f != N && f->op == OINDEX) {
	//		gc.Regalloc(&nod, &regnode, Z);
	//		v = constnode.vconst;
	//		gc.Cgen(f->right, &nod);
	//		constnode.vconst = v;
	//		idx.reg = nod.reg;
	//		gc.Regfree(&nod);
	//	}
	//	if(t != N && t->op == OINDEX) {
	//		gc.Regalloc(&nod, &regnode, Z);
	//		v = constnode.vconst;
	//		gc.Cgen(t->right, &nod);
	//		constnode.vconst = v;
	//		idx.reg = nod.reg;
	//		gc.Regfree(&nod);
	//	}

	if f != nil && f.Op == gc.OADDR && (as == x86.AMOVL || as == x86.AMOVQ) {
		// Turn MOVL $xxx into LEAL xxx.
		// These should be equivalent but most of the backend
		// only expects to see LEAL, because that's what we had
		// historically generated. Various hidden assumptions are baked in by now.
		if as == x86.AMOVL {
			as = x86.ALEAL
		} else {
			as = x86.ALEAQ
		}
		f = f.Left
	}

	switch as {
	case x86.AMOVB,
		x86.AMOVW,
		x86.AMOVL,
		x86.AMOVQ,
		x86.AMOVSS,
		x86.AMOVSD:
		if f != nil && t != nil && samaddr(f, t) {
			return nil
		}

	case x86.ALEAQ:
		if f != nil && gc.Isconst(f, gc.CTNIL) {
			gc.Fatal("gins LEAQ nil %v", f.Type)
		}
	}

	p := gc.Prog(as)
	gc.Naddr(&p.From, f)
	gc.Naddr(&p.To, t)

	if gc.Debug['g'] != 0 {
		fmt.Printf("%v\n", p)
	}

	w := int32(0)
	switch as {
	case x86.AMOVB:
		w = 1

	case x86.AMOVW:
		w = 2

	case x86.AMOVL:
		w = 4

	case x86.AMOVQ:
		w = 8
	}

	if w != 0 && ((f != nil && p.From.Width < int64(w)) || (t != nil && p.To.Width > int64(w))) {
		gc.Dump("f", f)
		gc.Dump("t", t)
		gc.Fatal("bad width: %v (%d, %d)\n", p, p.From.Width, p.To.Width)
	}

	if p.To.Type == obj.TYPE_ADDR && w > 0 {
		gc.Fatal("bad use of addr: %v", p)
	}

	return p
}

/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as obj.As, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			return false
		}
		v := n.Int64()
		switch as {
		default:
			return false

		// operations that can cope with a 32-bit immediate
		// TODO(mundaym): logical operations can work on high bits
		case s390x.AADD,
			s390x.AADDC,
			s390x.ASUB,
			s390x.AMULLW,
			s390x.AAND,
			s390x.AOR,
			s390x.AXOR,
			s390x.ASLD,
			s390x.ASLW,
			s390x.ASRAW,
			s390x.ASRAD,
			s390x.ASRW,
			s390x.ASRD,
			s390x.AMOVB,
			s390x.AMOVBZ,
			s390x.AMOVH,
			s390x.AMOVHZ,
			s390x.AMOVW,
			s390x.AMOVWZ,
			s390x.AMOVD:
			if int64(int32(v)) != v {
				return false
			}

		// for comparisons avoid immediates unless they can
		// fit into a int8/uint8
		// this favours combined compare and branch instructions
		case s390x.ACMP:
			if int64(int8(v)) != v {
				return false
			}
		case s390x.ACMPU:
			if int64(uint8(v)) != v {
				return false
			}
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			// check that the offset fits into a 12-bit displacement
			if n1.Xoffset < 0 || n1.Xoffset >= (1<<12)-8 {
				sudoclean()
				return false
//.........這裏部分代碼省略.........