go/src/cmd/8g/gsubr.c

// Derived from Inferno utils/8c/txt.c
// http://code.google.com/p/inferno-os/source/browse/utils/8c/txt.c
//
//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
//	Portions Copyright © 1997-1999 Vita Nuova Limited
//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
//	Portions Copyright © 2004,2006 Bruce Ellis
//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#include <u.h>
#include <libc.h>
#include "gg.h"

// TODO(rsc): Can make this bigger if we move
// the text segment up higher in 8l for all GOOS.
uint32 unmappedzero = 4096;

#define	CASE(a,b)	(((a)<<16)|((b)<<0))

void
clearp(Prog *p)
{
	p->as = AEND;
	p->from.type = D_NONE;
	p->from.index = D_NONE;
	p->to.type = D_NONE;
	p->to.index = D_NONE;
	p->loc = pcloc;
	pcloc++;
}

static int ddumped;
static Prog *dfirst;
static Prog *dpc;

/*
 * generate and return proc with p->as = as,
 * linked into program.  pc is next instruction.
 */
Prog*
prog(int as)
{
	Prog *p;

	if(as == ADATA || as == AGLOBL) {
		if(ddumped)
			fatal("already dumped data");
		if(dpc == nil) {
			dpc = mal(sizeof(*dpc));
			dfirst = dpc;
		}
		p = dpc;
		dpc = mal(sizeof(*dpc));
		p->link = dpc;
	} else {
		p = pc;
		pc = mal(sizeof(*pc));
		clearp(pc);
		p->link = pc;
	}

	if(lineno == 0) {
		if(debug['K'])
			warn("prog: line 0");
	}

	p->as = as;
	p->lineno = lineno;
	return p;
}

void
dumpdata(void)
{
	ddumped = 1;
	if(dfirst == nil)
		return;
	newplist();
	*pc = *dfirst;
	pc = dpc;
	clearp(pc);
}

/*
 * generate a branch.
 * t is ignored.
 * likely values are for branch prediction:
 *	-1 unlikely
 *	0 no opinion
 *	+1 likely
 */
Prog*
gbranch(int as, Type *t, int likely)
{
	Prog *p;

	USED(t);
	p = prog(as);
	p->to.type = D_BRANCH;
	p->to.branch = P;
	if(likely != 0) {
		p->from.type = D_CONST;
		p->from.offset = likely > 0;
	}
	return p;
}

/*
 * patch previous branch to jump to to.
 */
void
patch(Prog *p, Prog *to)
{
	if(p->to.type != D_BRANCH)
		fatal("patch: not a branch");
	p->to.branch = to;
	p->to.offset = to->loc;
}

Prog*
unpatch(Prog *p)
{
	Prog *q;

	if(p->to.type != D_BRANCH)
		fatal("unpatch: not a branch");
	q = p->to.branch;
	p->to.branch = P;
	p->to.offset = 0;
	return q;
}

/*
 * start a new Prog list.
 */
Plist*
newplist(void)
{
	Plist *pl;

	pl = mal(sizeof(*pl));
	if(plist == nil)
		plist = pl;
	else
		plast->link = pl;
	plast = pl;

	pc = mal(sizeof(*pc));
	clearp(pc);
	pl->firstpc = pc;

	return pl;
}

void
gused(Node *n)
{
	gins(ANOP, n, N);	// used
}

Prog*
gjmp(Prog *to)
{
	Prog *p;

	p = gbranch(AJMP, T, 0);
	if(to != P)
		patch(p, to);
	return p;
}

void
ggloblnod(Node *nam, int32 width)
{
	Prog *p;

	p = gins(AGLOBL, nam, N);
	p->lineno = nam->lineno;
	p->to.sym = S;
	p->to.type = D_CONST;
	p->to.offset = width;
	if(nam->readonly)
		p->from.scale = RODATA;
	if(nam->type != T && !haspointers(nam->type))
		p->from.scale |= NOPTR;
}

void
ggloblsym(Sym *s, int32 width, int dupok, int rodata)
{
	Prog *p;

	p = gins(AGLOBL, N, N);
	p->from.type = D_EXTERN;
	p->from.index = D_NONE;
	p->from.sym = s;
	p->to.type = D_CONST;
	p->to.index = D_NONE;
	p->to.offset = width;
	if(dupok)
		p->from.scale |= DUPOK;
	if(rodata)
		p->from.scale |= RODATA;
}

int
isfat(Type *t)
{
	if(t != T)
	switch(t->etype) {
	case TSTRUCT:
	case TARRAY:
	case TSTRING:
	case TINTER:	// maybe remove later
		return 1;
	}
	return 0;
}

/*
 * naddr of func generates code for address of func.
 * if using opcode that can take address implicitly,
 * call afunclit to fix up the argument.
 */
void
afunclit(Addr *a)
{
	if(a->type == D_ADDR && a->index == D_EXTERN) {
		a->type = D_EXTERN;
		a->index = D_NONE;
	}
}

/*
 * return Axxx for Oxxx on type t.
 */
int
optoas(int op, Type *t)
{
	int a;

	if(t == T)
		fatal("optoas: t is nil");

	a = AGOK;
	switch(CASE(op, simtype[t->etype])) {
	default:
		fatal("optoas: no entry %O-%T", op, t);
		break;

	case CASE(OADDR, TPTR32):
		a = ALEAL;
		break;

	case CASE(OEQ, TBOOL):
	case CASE(OEQ, TINT8):
	case CASE(OEQ, TUINT8):
	case CASE(OEQ, TINT16):
	case CASE(OEQ, TUINT16):
	case CASE(OEQ, TINT32):
	case CASE(OEQ, TUINT32):
	case CASE(OEQ, TINT64):
	case CASE(OEQ, TUINT64):
	case CASE(OEQ, TPTR32):
	case CASE(OEQ, TPTR64):
	case CASE(OEQ, TFLOAT32):
	case CASE(OEQ, TFLOAT64):
		a = AJEQ;
		break;

	case CASE(ONE, TBOOL):
	case CASE(ONE, TINT8):
	case CASE(ONE, TUINT8):
	case CASE(ONE, TINT16):
	case CASE(ONE, TUINT16):
	case CASE(ONE, TINT32):
	case CASE(ONE, TUINT32):
	case CASE(ONE, TINT64):
	case CASE(ONE, TUINT64):
	case CASE(ONE, TPTR32):
	case CASE(ONE, TPTR64):
	case CASE(ONE, TFLOAT32):
	case CASE(ONE, TFLOAT64):
		a = AJNE;
		break;

	case CASE(OLT, TINT8):
	case CASE(OLT, TINT16):
	case CASE(OLT, TINT32):
	case CASE(OLT, TINT64):
		a = AJLT;
		break;

	case CASE(OLT, TUINT8):
	case CASE(OLT, TUINT16):
	case CASE(OLT, TUINT32):
	case CASE(OLT, TUINT64):
		a = AJCS;
		break;

	case CASE(OLE, TINT8):
	case CASE(OLE, TINT16):
	case CASE(OLE, TINT32):
	case CASE(OLE, TINT64):
		a = AJLE;
		break;

	case CASE(OLE, TUINT8):
	case CASE(OLE, TUINT16):
	case CASE(OLE, TUINT32):
	case CASE(OLE, TUINT64):
		a = AJLS;
		break;

	case CASE(OGT, TINT8):
	case CASE(OGT, TINT16):
	case CASE(OGT, TINT32):
	case CASE(OGT, TINT64):
		a = AJGT;
		break;

	case CASE(OGT, TUINT8):
	case CASE(OGT, TUINT16):
	case CASE(OGT, TUINT32):
	case CASE(OGT, TUINT64):
	case CASE(OLT, TFLOAT32):
	case CASE(OLT, TFLOAT64):
		a = AJHI;
		break;

	case CASE(OGE, TINT8):
	case CASE(OGE, TINT16):
	case CASE(OGE, TINT32):
	case CASE(OGE, TINT64):
		a = AJGE;
		break;

	case CASE(OGE, TUINT8):
	case CASE(OGE, TUINT16):
	case CASE(OGE, TUINT32):
	case CASE(OGE, TUINT64):
	case CASE(OLE, TFLOAT32):
	case CASE(OLE, TFLOAT64):
		a = AJCC;
		break;

	case CASE(OCMP, TBOOL):
	case CASE(OCMP, TINT8):
	case CASE(OCMP, TUINT8):
		a = ACMPB;
		break;

	case CASE(OCMP, TINT16):
	case CASE(OCMP, TUINT16):
		a = ACMPW;
		break;

	case CASE(OCMP, TINT32):
	case CASE(OCMP, TUINT32):
	case CASE(OCMP, TPTR32):
		a = ACMPL;
		break;

	case CASE(OAS, TBOOL):
	case CASE(OAS, TINT8):
	case CASE(OAS, TUINT8):
		a = AMOVB;
		break;

	case CASE(OAS, TINT16):
	case CASE(OAS, TUINT16):
		a = AMOVW;
		break;

	case CASE(OAS, TINT32):
	case CASE(OAS, TUINT32):
	case CASE(OAS, TPTR32):
		a = AMOVL;
		break;

	case CASE(OADD, TINT8):
	case CASE(OADD, TUINT8):
		a = AADDB;
		break;

	case CASE(OADD, TINT16):
	case CASE(OADD, TUINT16):
		a = AADDW;
		break;

	case CASE(OADD, TINT32):
	case CASE(OADD, TUINT32):
	case CASE(OADD, TPTR32):
		a = AADDL;
		break;

	case CASE(OSUB, TINT8):
	case CASE(OSUB, TUINT8):
		a = ASUBB;
		break;

	case CASE(OSUB, TINT16):
	case CASE(OSUB, TUINT16):
		a = ASUBW;
		break;

	case CASE(OSUB, TINT32):
	case CASE(OSUB, TUINT32):
	case CASE(OSUB, TPTR32):
		a = ASUBL;
		break;

	case CASE(OINC, TINT8):
	case CASE(OINC, TUINT8):
		a = AINCB;
		break;

	case CASE(OINC, TINT16):
	case CASE(OINC, TUINT16):
		a = AINCW;
		break;

	case CASE(OINC, TINT32):
	case CASE(OINC, TUINT32):
	case CASE(OINC, TPTR32):
		a = AINCL;
		break;

	case CASE(ODEC, TINT8):
	case CASE(ODEC, TUINT8):
		a = ADECB;
		break;

	case CASE(ODEC, TINT16):
	case CASE(ODEC, TUINT16):
		a = ADECW;
		break;

	case CASE(ODEC, TINT32):
	case CASE(ODEC, TUINT32):
	case CASE(ODEC, TPTR32):
		a = ADECL;
		break;

	case CASE(OCOM, TINT8):
	case CASE(OCOM, TUINT8):
		a = ANOTB;
		break;

	case CASE(OCOM, TINT16):
	case CASE(OCOM, TUINT16):
		a = ANOTW;
		break;

	case CASE(OCOM, TINT32):
	case CASE(OCOM, TUINT32):
	case CASE(OCOM, TPTR32):
		a = ANOTL;
		break;

	case CASE(OMINUS, TINT8):
	case CASE(OMINUS, TUINT8):
		a = ANEGB;
		break;

	case CASE(OMINUS, TINT16):
	case CASE(OMINUS, TUINT16):
		a = ANEGW;
		break;

	case CASE(OMINUS, TINT32):
	case CASE(OMINUS, TUINT32):
	case CASE(OMINUS, TPTR32):
		a = ANEGL;
		break;

	case CASE(OAND, TINT8):
	case CASE(OAND, TUINT8):
		a = AANDB;
		break;

	case CASE(OAND, TINT16):
	case CASE(OAND, TUINT16):
		a = AANDW;
		break;

	case CASE(OAND, TINT32):
	case CASE(OAND, TUINT32):
	case CASE(OAND, TPTR32):
		a = AANDL;
		break;

	case CASE(OOR, TINT8):
	case CASE(OOR, TUINT8):
		a = AORB;
		break;

	case CASE(OOR, TINT16):
	case CASE(OOR, TUINT16):
		a = AORW;
		break;

	case CASE(OOR, TINT32):
	case CASE(OOR, TUINT32):
	case CASE(OOR, TPTR32):
		a = AORL;
		break;

	case CASE(OXOR, TINT8):
	case CASE(OXOR, TUINT8):
		a = AXORB;
		break;

	case CASE(OXOR, TINT16):
	case CASE(OXOR, TUINT16):
		a = AXORW;
		break;

	case CASE(OXOR, TINT32):
	case CASE(OXOR, TUINT32):
	case CASE(OXOR, TPTR32):
		a = AXORL;
		break;

	case CASE(OLROT, TINT8):
	case CASE(OLROT, TUINT8):
		a = AROLB;
		break;

	case CASE(OLROT, TINT16):
	case CASE(OLROT, TUINT16):
		a = AROLW;
		break;

	case CASE(OLROT, TINT32):
	case CASE(OLROT, TUINT32):
	case CASE(OLROT, TPTR32):
		a = AROLL;
		break;

	case CASE(OLSH, TINT8):
	case CASE(OLSH, TUINT8):
		a = ASHLB;
		break;

	case CASE(OLSH, TINT16):
	case CASE(OLSH, TUINT16):
		a = ASHLW;
		break;

	case CASE(OLSH, TINT32):
	case CASE(OLSH, TUINT32):
	case CASE(OLSH, TPTR32):
		a = ASHLL;
		break;

	case CASE(ORSH, TUINT8):
		a = ASHRB;
		break;

	case CASE(ORSH, TUINT16):
		a = ASHRW;
		break;

	case CASE(ORSH, TUINT32):
	case CASE(ORSH, TPTR32):
		a = ASHRL;
		break;

	case CASE(ORSH, TINT8):
		a = ASARB;
		break;

	case CASE(ORSH, TINT16):
		a = ASARW;
		break;

	case CASE(ORSH, TINT32):
		a = ASARL;
		break;

	case CASE(OMUL, TINT8):
	case CASE(OMUL, TUINT8):
		a = AIMULB;
		break;

	case CASE(OMUL, TINT16):
	case CASE(OMUL, TUINT16):
		a = AIMULW;
		break;

	case CASE(OMUL, TINT32):
	case CASE(OMUL, TUINT32):
	case CASE(OMUL, TPTR32):
		a = AIMULL;
		break;

	case CASE(ODIV, TINT8):
	case CASE(OMOD, TINT8):
		a = AIDIVB;
		break;

	case CASE(ODIV, TUINT8):
	case CASE(OMOD, TUINT8):
		a = ADIVB;
		break;

	case CASE(ODIV, TINT16):
	case CASE(OMOD, TINT16):
		a = AIDIVW;
		break;

	case CASE(ODIV, TUINT16):
	case CASE(OMOD, TUINT16):
		a = ADIVW;
		break;

	case CASE(ODIV, TINT32):
	case CASE(OMOD, TINT32):
		a = AIDIVL;
		break;

	case CASE(ODIV, TUINT32):
	case CASE(ODIV, TPTR32):
	case CASE(OMOD, TUINT32):
	case CASE(OMOD, TPTR32):
		a = ADIVL;
		break;

	case CASE(OEXTEND, TINT16):
		a = ACWD;
		break;

	case CASE(OEXTEND, TINT32):
		a = ACDQ;
		break;
	}
	return a;
}

#define FCASE(a, b, c)  (((a)<<16)|((b)<<8)|(c))
int
foptoas(int op, Type *t, int flg)
{
	int et;

	et = simtype[t->etype];

	// If we need Fpop, it means we're working on
	// two different floating-point registers, not memory.
	// There the instruction only has a float64 form.
	if(flg & Fpop)
		et = TFLOAT64;

	// clear Frev if unneeded
	switch(op) {
	case OADD:
	case OMUL:
		flg &= ~Frev;
		break;
	}

	switch(FCASE(op, et, flg)) {
	case FCASE(OADD, TFLOAT32, 0):
		return AFADDF;
	case FCASE(OADD, TFLOAT64, 0):
		return AFADDD;
	case FCASE(OADD, TFLOAT64, Fpop):
		return AFADDDP;

	case FCASE(OSUB, TFLOAT32, 0):
		return AFSUBF;
	case FCASE(OSUB, TFLOAT32, Frev):
		return AFSUBRF;

	case FCASE(OSUB, TFLOAT64, 0):
		return AFSUBD;
	case FCASE(OSUB, TFLOAT64, Frev):
		return AFSUBRD;
	case FCASE(OSUB, TFLOAT64, Fpop):
		return AFSUBDP;
	case FCASE(OSUB, TFLOAT64, Fpop|Frev):
		return AFSUBRDP;

	case FCASE(OMUL, TFLOAT32, 0):
		return AFMULF;
	case FCASE(OMUL, TFLOAT64, 0):
		return AFMULD;
	case FCASE(OMUL, TFLOAT64, Fpop):
		return AFMULDP;

	case FCASE(ODIV, TFLOAT32, 0):
		return AFDIVF;
	case FCASE(ODIV, TFLOAT32, Frev):
		return AFDIVRF;

	case FCASE(ODIV, TFLOAT64, 0):
		return AFDIVD;
	case FCASE(ODIV, TFLOAT64, Frev):
		return AFDIVRD;
	case FCASE(ODIV, TFLOAT64, Fpop):
		return AFDIVDP;
	case FCASE(ODIV, TFLOAT64, Fpop|Frev):
		return AFDIVRDP;

	case FCASE(OCMP, TFLOAT32, 0):
		return AFCOMF;
	case FCASE(OCMP, TFLOAT32, Fpop):
		return AFCOMFP;
	case FCASE(OCMP, TFLOAT64, 0):
		return AFCOMD;
	case FCASE(OCMP, TFLOAT64, Fpop):
		return AFCOMDP;
	case FCASE(OCMP, TFLOAT64, Fpop2):
		return AFCOMDPP;
	
	case FCASE(OMINUS, TFLOAT32, 0):
		return AFCHS;
	case FCASE(OMINUS, TFLOAT64, 0):
		return AFCHS;
	}

	fatal("foptoas %O %T %#x", op, t, flg);
	return 0;
}

static	int	resvd[] =
{
//	D_DI,	// for movstring
//	D_SI,	// for movstring

	D_AX,	// for divide
	D_CX,	// for shift
	D_DX,	// for divide
	D_SP,	// for stack

	D_BL,	// because D_BX can be allocated
	D_BH,
};

void
ginit(void)
{
	int i;

	for(i=0; i<nelem(reg); i++)
		reg[i] = 1;
	for(i=D_AX; i<=D_DI; i++)
		reg[i] = 0;
	for(i=0; i<nelem(resvd); i++)
		reg[resvd[i]]++;
}

uintptr regpc[D_NONE];

void
gclean(void)
{
	int i;

	for(i=0; i<nelem(resvd); i++)
		reg[resvd[i]]--;

	for(i=D_AX; i<=D_DI; i++)
		if(reg[i])
			yyerror("reg %R left allocated at %ux", i, regpc[i]);
}

int32
anyregalloc(void)
{
	int i, j;

	for(i=D_AX; i<=D_DI; i++) {
		if(reg[i] == 0)
			goto ok;
		for(j=0; j<nelem(resvd); j++)
			if(resvd[j] == i)
				goto ok;
		return 1;
	ok:;
	}
	return 0;
}

/*
 * allocate register of type t, leave in n.
 * if o != N, o is desired fixed register.
 * caller must regfree(n).
 */
void
regalloc(Node *n, Type *t, Node *o)
{
	int i, et;

	if(t == T)
		fatal("regalloc: t nil");
	et = simtype[t->etype];

	switch(et) {
	case TINT8:
	case TUINT8:
	case TINT16:
	case TUINT16:
	case TINT32:
	case TUINT32:
	case TINT64:
	case TUINT64:
	case TPTR32:
	case TPTR64:
	case TBOOL:
		if(o != N && o->op == OREGISTER) {
			i = o->val.u.reg;
			if(i >= D_AX && i <= D_DI)
				goto out;
		}
		for(i=D_AX; i<=D_DI; i++)
			if(reg[i] == 0)
				goto out;

		fprint(2, "registers allocated at\n");
		for(i=D_AX; i<=D_DI; i++)
			fprint(2, "\t%R\t%#lux\n", i, regpc[i]);
		yyerror("out of fixed registers");
		goto err;

	case TFLOAT32:
	case TFLOAT64:
		i = D_F0;
		goto out;
	}
	yyerror("regalloc: unknown type %T", t);

err:
	nodreg(n, t, 0);
	return;

out:
	if (i == D_SP)
		print("alloc SP\n");
	if(reg[i] == 0) {
		regpc[i] = (uintptr)getcallerpc(&n);
		if(i == D_AX || i == D_CX || i == D_DX || i == D_SP) {
			dump("regalloc-o", o);
			fatal("regalloc %R", i);
		}
	}
	reg[i]++;
	nodreg(n, t, i);
}

void
regfree(Node *n)
{
	int i;
	
	if(n->op == ONAME)
		return;
	if(n->op != OREGISTER && n->op != OINDREG)
		fatal("regfree: not a register");
	i = n->val.u.reg;
	if(i == D_SP)
		return;
	if(i < 0 || i >= nelem(reg))
		fatal("regfree: reg out of range");
	if(reg[i] <= 0)
		fatal("regfree: reg not allocated");
	reg[i]--;
	if(reg[i] == 0 && (i == D_AX || i == D_CX || i == D_DX || i == D_SP))
		fatal("regfree %R", i);
}

/*
 * initialize n to be register r of type t.
 */
void
nodreg(Node *n, Type *t, int r)
{
	if(t == T)
		fatal("nodreg: t nil");

	memset(n, 0, sizeof(*n));
	n->op = OREGISTER;
	n->addable = 1;
	ullmancalc(n);
	n->val.u.reg = r;
	n->type = t;
}

/*
 * initialize n to be indirect of register r; n is type t.
 */
void
nodindreg(Node *n, Type *t, int r)
{
	nodreg(n, t, r);
	n->op = OINDREG;
}

Node*
nodarg(Type *t, int fp)
{
	Node *n;
	Type *first;
	Iter savet;

	// entire argument struct, not just one arg
	switch(t->etype) {
	default:
		fatal("nodarg %T", t);

	case TSTRUCT:
		if(!t->funarg)
			fatal("nodarg: TSTRUCT but not funarg");
		n = nod(ONAME, N, N);
		n->sym = lookup(".args");
		n->type = t;
		first = structfirst(&savet, &t);
		if(first == nil)
			fatal("nodarg: bad struct");
		if(first->width == BADWIDTH)
			fatal("nodarg: offset not computed for %T", t);
		n->xoffset = first->width;
		n->addable = 1;
		break;

	case TFIELD:
		n = nod(ONAME, N, N);
		n->type = t->type;
		n->sym = t->sym;
		if(t->width == BADWIDTH)
			fatal("nodarg: offset not computed for %T", t);
		n->xoffset = t->width;
		n->addable = 1;
		n->orig = t->nname;
		break;
	}
	
	// Rewrite argument named _ to __,
	// or else the assignment to _ will be
	// discarded during code generation.
	if(isblank(n))
		n->sym = lookup("__");

	switch(fp) {
	default:
		fatal("nodarg %T %d", t, fp);

	case 0:		// output arg
		n->op = OINDREG;
		n->val.u.reg = D_SP;
		break;

	case 1:		// input arg
		n->class = PPARAM;
		break;
	}

	n->typecheck = 1;
	return n;
}

/*
 * generate
 *	as $c, reg
 */
void
gconreg(int as, vlong c, int reg)
{
	Node n1, n2;

	nodconst(&n1, types[TINT64], c);
	nodreg(&n2, types[TINT64], reg);
	gins(as, &n1, &n2);
}

/*
 * swap node contents
 */
void
nswap(Node *a, Node *b)
{
	Node t;

	t = *a;
	*a = *b;
	*b = t;
}

/*
 * return constant i node.
 * overwritten by next call, but useful in calls to gins.
 */
Node*
ncon(uint32 i)
{
	static Node n;

	if(n.type == T)
		nodconst(&n, types[TUINT32], 0);
	mpmovecfix(n.val.u.xval, i);
	return &n;
}

/*
 * Is this node a memory operand?
 */
int
ismem(Node *n)
{
	switch(n->op) {
	case OITAB:
	case OLEN:
	case OCAP:
	case OINDREG:
	case ONAME:
	case OPARAM:
		return 1;
	}
	return 0;
}

Node sclean[10];
int nsclean;

/*
 * n is a 64-bit value.  fill in lo and hi to refer to its 32-bit halves.
 */
void
split64(Node *n, Node *lo, Node *hi)
{
	Node n1;
	int64 i;

	if(!is64(n->type))
		fatal("split64 %T", n->type);

	sclean[nsclean].op = OEMPTY;
	if(nsclean >= nelem(sclean))
		fatal("split64 clean");
	nsclean++;
	switch(n->op) {
	default:
		if(!dotaddable(n, &n1)) {
			igen(n, &n1, N);
			sclean[nsclean-1] = n1;
		}
		n = &n1;
		goto common;
	case ONAME:
		if(n->class == PPARAMREF) {
			cgen(n->heapaddr, &n1);
			sclean[nsclean-1] = n1;
			// fall through.
			n = &n1;
		}
		goto common;
	case OINDREG:
	common:
		*lo = *n;
		*hi = *n;
		lo->type = types[TUINT32];
		if(n->type->etype == TINT64)
			hi->type = types[TINT32];
		else
			hi->type = types[TUINT32];
		hi->xoffset += 4;
		break;

	case OLITERAL:
		convconst(&n1, n->type, &n->val);
		i = mpgetfix(n1.val.u.xval);
		nodconst(lo, types[TUINT32], (uint32)i);
		i >>= 32;
		if(n->type->etype == TINT64)
			nodconst(hi, types[TINT32], (int32)i);
		else
			nodconst(hi, types[TUINT32], (uint32)i);
		break;
	}
}

void
splitclean(void)
{
	if(nsclean <= 0)
		fatal("splitclean");
	nsclean--;
	if(sclean[nsclean].op != OEMPTY)
		regfree(&sclean[nsclean]);
}

/*
 * set up nodes representing fp constants
 */
Node zerof;
Node two64f;
Node two63f;

void
bignodes(void)
{
	static int did;

	if(did)
		return;
	did = 1;

	two64f = *ncon(0);
	two64f.type = types[TFLOAT64];
	two64f.val.ctype = CTFLT;
	two64f.val.u.fval = mal(sizeof *two64f.val.u.fval);
	mpmovecflt(two64f.val.u.fval, 18446744073709551616.);

	two63f = two64f;
	two63f.val.u.fval = mal(sizeof *two63f.val.u.fval);
	mpmovecflt(two63f.val.u.fval, 9223372036854775808.);

	zerof = two64f;
	zerof.val.u.fval = mal(sizeof *zerof.val.u.fval);
	mpmovecflt(zerof.val.u.fval, 0);
}

void
memname(Node *n, Type *t)
{
	tempname(n, t);
	strcpy(namebuf, n->sym->name);
	namebuf[0] = '.';	// keep optimizer from registerizing
	n->sym = lookup(namebuf);
	n->orig->sym = n->sym;
}

void
gmove(Node *f, Node *t)
{
	int a, ft, tt;
	Type *cvt;
	Node r1, r2, t1, t2, flo, fhi, tlo, thi, con, f0, f1, ax, dx, cx;
	Prog *p1, *p2, *p3;

	if(debug['M'])
		print("gmove %N -> %N\n", f, t);

	ft = simsimtype(f->type);
	tt = simsimtype(t->type);
	cvt = t->type;

	if(iscomplex[ft] || iscomplex[tt]) {
		complexmove(f, t);
		return;
	}

	// cannot have two integer memory operands;
	// except 64-bit, which always copies via registers anyway.
	if(isint[ft] && isint[tt] && !is64(f->type) && !is64(t->type) && ismem(f) && ismem(t))
		goto hard;

	// convert constant to desired type
	if(f->op == OLITERAL) {
		if(tt == TFLOAT32)
			convconst(&con, types[TFLOAT64], &f->val);
		else
			convconst(&con, t->type, &f->val);
		f = &con;
		ft = simsimtype(con.type);

		// some constants can't move directly to memory.
		if(ismem(t)) {
			// float constants come from memory.
			if(isfloat[tt])
				goto hard;
		}
	}

	// value -> value copy, only one memory operand.
	// figure out the instruction to use.
	// break out of switch for one-instruction gins.
	// goto rdst for "destination must be register".
	// goto hard for "convert to cvt type first".
	// otherwise handle and return.

	switch(CASE(ft, tt)) {
	default:
		goto fatal;

	/*
	 * integer copy and truncate
	 */
	case CASE(TINT8, TINT8):	// same size
	case CASE(TINT8, TUINT8):
	case CASE(TUINT8, TINT8):
	case CASE(TUINT8, TUINT8):
		a = AMOVB;
		break;

	case CASE(TINT16, TINT8):	// truncate
	case CASE(TUINT16, TINT8):
	case CASE(TINT32, TINT8):
	case CASE(TUINT32, TINT8):
	case CASE(TINT16, TUINT8):
	case CASE(TUINT16, TUINT8):
	case CASE(TINT32, TUINT8):
	case CASE(TUINT32, TUINT8):
		a = AMOVB;
		goto rsrc;

	case CASE(TINT64, TINT8):	// truncate low word
	case CASE(TUINT64, TINT8):
	case CASE(TINT64, TUINT8):
	case CASE(TUINT64, TUINT8):
		split64(f, &flo, &fhi);
		nodreg(&r1, t->type, D_AX);
		gmove(&flo, &r1);
		gins(AMOVB, &r1, t);
		splitclean();
		return;

	case CASE(TINT16, TINT16):	// same size
	case CASE(TINT16, TUINT16):
	case CASE(TUINT16, TINT16):
	case CASE(TUINT16, TUINT16):
		a = AMOVW;
		break;

	case CASE(TINT32, TINT16):	// truncate
	case CASE(TUINT32, TINT16):
	case CASE(TINT32, TUINT16):
	case CASE(TUINT32, TUINT16):
		a = AMOVW;
		goto rsrc;

	case CASE(TINT64, TINT16):	// truncate low word
	case CASE(TUINT64, TINT16):
	case CASE(TINT64, TUINT16):
	case CASE(TUINT64, TUINT16):
		split64(f, &flo, &fhi);
		nodreg(&r1, t->type, D_AX);
		gmove(&flo, &r1);
		gins(AMOVW, &r1, t);
		splitclean();
		return;

	case CASE(TINT32, TINT32):	// same size
	case CASE(TINT32, TUINT32):
	case CASE(TUINT32, TINT32):
	case CASE(TUINT32, TUINT32):
		a = AMOVL;
		break;

	case CASE(TINT64, TINT32):	// truncate
	case CASE(TUINT64, TINT32):
	case CASE(TINT64, TUINT32):
	case CASE(TUINT64, TUINT32):
		split64(f, &flo, &fhi);
		nodreg(&r1, t->type, D_AX);
		gmove(&flo, &r1);
		gins(AMOVL, &r1, t);
		splitclean();
		return;

	case CASE(TINT64, TINT64):	// same size
	case CASE(TINT64, TUINT64):
	case CASE(TUINT64, TINT64):
	case CASE(TUINT64, TUINT64):
		split64(f, &flo, &fhi);
		split64(t, &tlo, &thi);
		if(f->op == OLITERAL) {
			gins(AMOVL, &flo, &tlo);
			gins(AMOVL, &fhi, &thi);
		} else {
			nodreg(&r1, t->type, D_AX);
			nodreg(&r2, t->type, D_DX);
			gins(AMOVL, &flo, &r1);
			gins(AMOVL, &fhi, &r2);
			gins(AMOVL, &r1, &tlo);
			gins(AMOVL, &r2, &thi);
		}
		splitclean();
		splitclean();
		return;

	/*
	 * integer up-conversions
	 */
	case CASE(TINT8, TINT16):	// sign extend int8
	case CASE(TINT8, TUINT16):
		a = AMOVBWSX;
		goto rdst;
	case CASE(TINT8, TINT32):
	case CASE(TINT8, TUINT32):
		a = AMOVBLSX;
		goto rdst;
	case CASE(TINT8, TINT64):	// convert via int32
	case CASE(TINT8, TUINT64):
		cvt = types[TINT32];
		goto hard;

	case CASE(TUINT8, TINT16):	// zero extend uint8
	case CASE(TUINT8, TUINT16):
		a = AMOVBWZX;
		goto rdst;
	case CASE(TUINT8, TINT32):
	case CASE(TUINT8, TUINT32):
		a = AMOVBLZX;
		goto rdst;
	case CASE(TUINT8, TINT64):	// convert via uint32
	case CASE(TUINT8, TUINT64):
		cvt = types[TUINT32];
		goto hard;

	case CASE(TINT16, TINT32):	// sign extend int16
	case CASE(TINT16, TUINT32):
		a = AMOVWLSX;
		goto rdst;
	case CASE(TINT16, TINT64):	// convert via int32
	case CASE(TINT16, TUINT64):
		cvt = types[TINT32];
		goto hard;

	case CASE(TUINT16, TINT32):	// zero extend uint16
	case CASE(TUINT16, TUINT32):
		a = AMOVWLZX;
		goto rdst;
	case CASE(TUINT16, TINT64):	// convert via uint32
	case CASE(TUINT16, TUINT64):
		cvt = types[TUINT32];
		goto hard;

	case CASE(TINT32, TINT64):	// sign extend int32
	case CASE(TINT32, TUINT64):
		split64(t, &tlo, &thi);
		nodreg(&flo, tlo.type, D_AX);
		nodreg(&fhi, thi.type, D_DX);
		gmove(f, &flo);
		gins(ACDQ, N, N);
		gins(AMOVL, &flo, &tlo);
		gins(AMOVL, &fhi, &thi);
		splitclean();
		return;

	case CASE(TUINT32, TINT64):	// zero extend uint32
	case CASE(TUINT32, TUINT64):
		split64(t, &tlo, &thi);
		gmove(f, &tlo);
		gins(AMOVL, ncon(0), &thi);
		splitclean();
		return;

	/*
	* float to integer
	*/
	case CASE(TFLOAT32, TINT16):
	case CASE(TFLOAT32, TINT32):
	case CASE(TFLOAT32, TINT64):
	case CASE(TFLOAT64, TINT16):
	case CASE(TFLOAT64, TINT32):
	case CASE(TFLOAT64, TINT64):
		if(t->op == OREGISTER)
			goto hardmem;
		nodreg(&r1, types[ft], D_F0);
		if(f->op != OREGISTER) {
			if(ft == TFLOAT32)
				gins(AFMOVF, f, &r1);
			else
				gins(AFMOVD, f, &r1);
		}

		// set round to zero mode during conversion
		memname(&t1, types[TUINT16]);
		memname(&t2, types[TUINT16]);
		gins(AFSTCW, N, &t1);
		gins(AMOVW, ncon(0xf7f), &t2);
		gins(AFLDCW, &t2, N);
		if(tt == TINT16)
			gins(AFMOVWP, &r1, t);
		else if(tt == TINT32)
			gins(AFMOVLP, &r1, t);
		else
			gins(AFMOVVP, &r1, t);
		gins(AFLDCW, &t1, N);
		return;

	case CASE(TFLOAT32, TINT8):
	case CASE(TFLOAT32, TUINT16):
	case CASE(TFLOAT32, TUINT8):
	case CASE(TFLOAT64, TINT8):
	case CASE(TFLOAT64, TUINT16):
	case CASE(TFLOAT64, TUINT8):
		// convert via int32.
		tempname(&t1, types[TINT32]);
		gmove(f, &t1);
		switch(tt) {
		default:
			fatal("gmove %T", t);
		case TINT8:
			gins(ACMPL, &t1, ncon(-0x80));
			p1 = gbranch(optoas(OLT, types[TINT32]), T, -1);
			gins(ACMPL, &t1, ncon(0x7f));
			p2 = gbranch(optoas(OGT, types[TINT32]), T, -1);
			p3 = gbranch(AJMP, T, 0);
			patch(p1, pc);
			patch(p2, pc);
			gmove(ncon(-0x80), &t1);
			patch(p3, pc);
			gmove(&t1, t);
			break;
		case TUINT8:
			gins(ATESTL, ncon(0xffffff00), &t1);
			p1 = gbranch(AJEQ, T, +1);
			gins(AMOVL, ncon(0), &t1);
			patch(p1, pc);
			gmove(&t1, t);
			break;
		case TUINT16:
			gins(ATESTL, ncon(0xffff0000), &t1);
			p1 = gbranch(AJEQ, T, +1);
			gins(AMOVL, ncon(0), &t1);
			patch(p1, pc);
			gmove(&t1, t);
			break;
		}
		return;

	case CASE(TFLOAT32, TUINT32):
	case CASE(TFLOAT64, TUINT32):
		// convert via int64.
		tempname(&t1, types[TINT64]);
		gmove(f, &t1);
		split64(&t1, &tlo, &thi);
		gins(ACMPL, &thi, ncon(0));
		p1 = gbranch(AJEQ, T, +1);
		gins(AMOVL, ncon(0), &tlo);
		patch(p1, pc);
		gmove(&tlo, t);
		splitclean();
		return;

	case CASE(TFLOAT32, TUINT64):
	case CASE(TFLOAT64, TUINT64):
		bignodes();
		nodreg(&f0, types[ft], D_F0);
		nodreg(&f1, types[ft], D_F0 + 1);
		nodreg(&ax, types[TUINT16], D_AX);

		gmove(f, &f0);

		// if 0 > v { answer = 0 }
		gmove(&zerof, &f0);
		gins(AFUCOMIP, &f0, &f1);
		p1 = gbranch(optoas(OGT, types[tt]), T, 0);
		// if 1<<64 <= v { answer = 0 too }
		gmove(&two64f, &f0);
		gins(AFUCOMIP, &f0, &f1);
		p2 = gbranch(optoas(OGT, types[tt]), T, 0);
		patch(p1, pc);
		gins(AFMOVVP, &f0, t);	// don't care about t, but will pop the stack
		split64(t, &tlo, &thi);
		gins(AMOVL, ncon(0), &tlo);
		gins(AMOVL, ncon(0), &thi);
		splitclean();
		p1 = gbranch(AJMP, T, 0);
		patch(p2, pc);

		// in range; algorithm is:
		//	if small enough, use native float64 -> int64 conversion.
		//	otherwise, subtract 2^63, convert, and add it back.

		// set round to zero mode during conversion
		memname(&t1, types[TUINT16]);
		memname(&t2, types[TUINT16]);
		gins(AFSTCW, N, &t1);
		gins(AMOVW, ncon(0xf7f), &t2);
		gins(AFLDCW, &t2, N);

		// actual work
		gmove(&two63f, &f0);
		gins(AFUCOMIP, &f0, &f1);
		p2 = gbranch(optoas(OLE, types[tt]), T, 0);
		gins(AFMOVVP, &f0, t);
		p3 = gbranch(AJMP, T, 0);
		patch(p2, pc);
		gmove(&two63f, &f0);
		gins(AFSUBDP, &f0, &f1);
		gins(AFMOVVP, &f0, t);
		split64(t, &tlo, &thi);
		gins(AXORL, ncon(0x80000000), &thi);	// + 2^63
		patch(p3, pc);
		splitclean();
		// restore rounding mode
		gins(AFLDCW, &t1, N);

		patch(p1, pc);
		return;

	/*
	 * integer to float
	 */
	case CASE(TINT16, TFLOAT32):
	case CASE(TINT16, TFLOAT64):
	case CASE(TINT32, TFLOAT32):
	case CASE(TINT32, TFLOAT64):
	case CASE(TINT64, TFLOAT32):
	case CASE(TINT64, TFLOAT64):
		if(t->op != OREGISTER)
			goto hard;
		if(f->op == OREGISTER) {
			cvt = f->type;
			goto hardmem;
		}
		switch(ft) {
		case TINT16:
			a = AFMOVW;
			break;
		case TINT32:
			a = AFMOVL;
			break;
		default:
			a = AFMOVV;
			break;
		}
		break;

	case CASE(TINT8, TFLOAT32):
	case CASE(TINT8, TFLOAT64):
	case CASE(TUINT16, TFLOAT32):
	case CASE(TUINT16, TFLOAT64):
	case CASE(TUINT8, TFLOAT32):
	case CASE(TUINT8, TFLOAT64):
		// convert via int32 memory
		cvt = types[TINT32];
		goto hardmem;

	case CASE(TUINT32, TFLOAT32):
	case CASE(TUINT32, TFLOAT64):
		// convert via int64 memory
		cvt = types[TINT64];
		goto hardmem;

	case CASE(TUINT64, TFLOAT32):
	case CASE(TUINT64, TFLOAT64):
		// algorithm is:
		//	if small enough, use native int64 -> uint64 conversion.
		//	otherwise, halve (rounding to odd?), convert, and double.
		nodreg(&ax, types[TUINT32], D_AX);
		nodreg(&dx, types[TUINT32], D_DX);
		nodreg(&cx, types[TUINT32], D_CX);
		tempname(&t1, f->type);
		split64(&t1, &tlo, &thi);
		gmove(f, &t1);
		gins(ACMPL, &thi, ncon(0));
		p1 = gbranch(AJLT, T, 0);
		// native
		t1.type = types[TINT64];
		gmove(&t1, t);
		p2 = gbranch(AJMP, T, 0);
		// simulated
		patch(p1, pc);
		gmove(&tlo, &ax);
		gmove(&thi, &dx);
		p1 = gins(ASHRL, ncon(1), &ax);
		p1->from.index = D_DX;	// double-width shift DX -> AX
		p1->from.scale = 0;
		gins(AMOVL, ncon(0), &cx);
		gins(ASETCC, N, &cx);
		gins(AORL, &cx, &ax);
		gins(ASHRL, ncon(1), &dx);
		gmove(&dx, &thi);
		gmove(&ax, &tlo);
		nodreg(&r1, types[tt], D_F0);
		nodreg(&r2, types[tt], D_F0 + 1);
		gmove(&t1, &r1);	// t1.type is TINT64 now, set above
		gins(AFMOVD, &r1, &r1);
		gins(AFADDDP, &r1, &r2);
		gmove(&r1, t);
		patch(p2, pc);
		splitclean();
		return;

	/*
	 * float to float
	 */
	case CASE(TFLOAT32, TFLOAT32):
	case CASE(TFLOAT64, TFLOAT64):
		// The way the code generator uses floating-point
		// registers, a move from F0 to F0 is intended as a no-op.
		// On the x86, it's not: it pushes a second copy of F0
		// on the floating point stack.  So toss it away here.
		// Also, F0 is the *only* register we ever evaluate
		// into, so we should only see register/register as F0/F0.
		if(ismem(f) && ismem(t))
			goto hard;
		if(f->op == OREGISTER && t->op == OREGISTER) {
			if(f->val.u.reg != D_F0 || t->val.u.reg != D_F0)
				goto fatal;
			return;
		}
		a = AFMOVF;
		if(ft == TFLOAT64)
			a = AFMOVD;
		if(ismem(t)) {
			if(f->op != OREGISTER || f->val.u.reg != D_F0)
				fatal("gmove %N", f);
			a = AFMOVFP;
			if(ft == TFLOAT64)
				a = AFMOVDP;
		}
		break;

	case CASE(TFLOAT32, TFLOAT64):
		if(ismem(f) && ismem(t))
			goto hard;
		if(f->op == OREGISTER && t->op == OREGISTER) {
			if(f->val.u.reg != D_F0 || t->val.u.reg != D_F0)
				goto fatal;
			return;
		}
		if(f->op == OREGISTER)
			gins(AFMOVDP, f, t);
		else
			gins(AFMOVF, f, t);
		return;

	case CASE(TFLOAT64, TFLOAT32):
		if(ismem(f) && ismem(t))
			goto hard;
		if(f->op == OREGISTER && t->op == OREGISTER) {
			tempname(&r1, types[TFLOAT32]);
			gins(AFMOVFP, f, &r1);
			gins(AFMOVF, &r1, t);
			return;
		}
		if(f->op == OREGISTER)
			gins(AFMOVFP, f, t);
		else
			gins(AFMOVD, f, t);
		return;
	}

	gins(a, f, t);
	return;

rsrc:
	// requires register source
	regalloc(&r1, f->type, t);
	gmove(f, &r1);
	gins(a, &r1, t);
	regfree(&r1);
	return;

rdst:
	// requires register destination
	regalloc(&r1, t->type, t);
	gins(a, f, &r1);
	gmove(&r1, t);
	regfree(&r1);
	return;

hard:
	// requires register intermediate
	regalloc(&r1, cvt, t);
	gmove(f, &r1);
	gmove(&r1, t);
	regfree(&r1);
	return;

hardmem:
	// requires memory intermediate
	tempname(&r1, cvt);
	gmove(f, &r1);
	gmove(&r1, t);
	return;

fatal:
	// should not happen
	fatal("gmove %N -> %N", f, t);
}

int
samaddr(Node *f, Node *t)
{

	if(f->op != t->op)
		return 0;

	switch(f->op) {
	case OREGISTER:
		if(f->val.u.reg != t->val.u.reg)
			break;
		return 1;
	}
	return 0;
}
/*
 * generate one instruction:
 *	as f, t
 */
Prog*
gins(int as, Node *f, Node *t)
{
	Prog *p;
	Addr af, at;
	int w;

	if(as == AFMOVF && f && f->op == OREGISTER && t && t->op == OREGISTER)
		fatal("gins MOVF reg, reg");

	switch(as) {
	case AMOVB:
	case AMOVW:
	case AMOVL:
		if(f != N && t != N && samaddr(f, t))
			return nil;
		break;
	
	case ALEAL:
		if(f != N && isconst(f, CTNIL))
			fatal("gins LEAQ nil %T", f->type);
		break;
	}

	memset(&af, 0, sizeof af);
	memset(&at, 0, sizeof at);
	if(f != N)
		naddr(f, &af, 1);
	if(t != N)
		naddr(t, &at, 1);
	p = prog(as);
	if(f != N)
		p->from = af;
	if(t != N)
		p->to = at;
	if(debug['g'])
		print("%P\n", p);

	w = 0;
	switch(as) {
	case AMOVB:
		w = 1;
		break;
	case AMOVW:
		w = 2;
		break;
	case AMOVL:
		w = 4;
		break;
	}

	if(1 && w != 0 && f != N && (af.width > w || at.width > w)) {
		dump("bad width from:", f);
		dump("bad width to:", t);
		fatal("bad width: %P (%d, %d)\n", p, af.width, at.width);
	}

	return p;
}

// Generate an instruction referencing *n
// to force segv on nil pointer dereference.
void
checkref(Node *n)
{
	Node m;

	if(n->type->type->width < unmappedzero)
		return;

	regalloc(&m, types[TUINTPTR], n);
	cgen(n, &m);
	m.xoffset = 0;
	m.op = OINDREG;
	m.type = types[TUINT8];
	gins(ATESTB, nodintconst(0), &m);
	regfree(&m);
}

static void
checkoffset(Addr *a, int canemitcode)
{
	Prog *p;

	if(a->offset < unmappedzero)
		return;
	if(!canemitcode)
		fatal("checkoffset %#x, cannot emit code", a->offset);

	// cannot rely on unmapped nil page at 0 to catch
	// reference with large offset.  instead, emit explicit
	// test of 0(reg).
	p = gins(ATESTB, nodintconst(0), N);
	p->to = *a;
	p->to.offset = 0;
}

/*
 * generate code to compute n;
 * make a refer to result.
 */
void
naddr(Node *n, Addr *a, int canemitcode)
{
	a->scale = 0;
	a->index = D_NONE;
	a->type = D_NONE;
	a->gotype = S;
	a->node = N;
	if(n == N)
		return;

	switch(n->op) {
	default:
		fatal("naddr: bad %O %D", n->op, a);
		break;

	case OREGISTER:
		a->type = n->val.u.reg;
		a->sym = S;
		break;

	case OINDREG:
		a->type = n->val.u.reg+D_INDIR;
		a->sym = n->sym;
		a->offset = n->xoffset;
		break;

	case OPARAM:
		// n->left is PHEAP ONAME for stack parameter.
		// compute address of actual parameter on stack.
		a->etype = n->left->type->etype;
		a->width = n->left->type->width;
		a->offset = n->xoffset;
		a->sym = n->left->sym;
		a->type = D_PARAM;
		a->node = n->left->orig;
		break;

	case ONAME:
		a->etype = 0;
		a->width = 0;
		if(n->type != T) {
			a->etype = simtype[n->type->etype];
			dowidth(n->type);
			a->width = n->type->width;
			a->gotype = ngotype(n);
		}
		a->offset = n->xoffset;
		a->sym = n->sym;
		a->node = n->orig;
		//if(a->node >= (Node*)&n)
		//	fatal("stack node");
		if(a->sym == S)
			a->sym = lookup(".noname");
		if(n->method) {
			if(n->type != T)
			if(n->type->sym != S)
			if(n->type->sym->pkg != nil)
				a->sym = pkglookup(a->sym->name, n->type->sym->pkg);
		}

		switch(n->class) {
		default:
			fatal("naddr: ONAME class %S %d\n", n->sym, n->class);
		case PEXTERN:
			a->type = D_EXTERN;
			break;
		case PAUTO:
			a->type = D_AUTO;
			break;
		case PPARAM:
		case PPARAMOUT:
			a->type = D_PARAM;
			break;
		case PFUNC:
			a->index = D_EXTERN;
			a->type = D_ADDR;
			break;
		}
		break;

	case OLITERAL:
		switch(n->val.ctype) {
		default:
			fatal("naddr: const %lT", n->type);
			break;
		case CTFLT:
			a->type = D_FCONST;
			a->dval = mpgetflt(n->val.u.fval);
			break;
		case CTINT:
		case CTRUNE:
			a->sym = S;
			a->type = D_CONST;
			a->offset = mpgetfix(n->val.u.xval);
			break;
		case CTSTR:
			datagostring(n->val.u.sval, a);
			break;
		case CTBOOL:
			a->sym = S;
			a->type = D_CONST;
			a->offset = n->val.u.bval;
			break;
		case CTNIL:
			a->sym = S;
			a->type = D_CONST;
			a->offset = 0;
			break;
		}
		break;

	case OADDR:
		naddr(n->left, a, canemitcode);
		if(a->type >= D_INDIR) {
			a->type -= D_INDIR;
			break;
		}
		if(a->type == D_EXTERN || a->type == D_STATIC ||
		   a->type == D_AUTO || a->type == D_PARAM)
			if(a->index == D_NONE) {
				a->index = a->type;
				a->type = D_ADDR;
				break;
			}
		fatal("naddr: OADDR\n");
	
	case OITAB:
		// itable of interface value
		naddr(n->left, a, canemitcode);
		if(a->type == D_CONST && a->offset == 0)
			break;	// len(nil)
		a->etype = tptr;
		a->width = widthptr;
		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
			checkoffset(a, canemitcode);
		break;

	case OLEN:
		// len of string or slice
		naddr(n->left, a, canemitcode);
		if(a->type == D_CONST && a->offset == 0)
			break;	// len(nil)
		a->etype = TUINT32;
		a->offset += Array_nel;
		a->width = 4;
		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
			checkoffset(a, canemitcode);
		break;

	case OCAP:
		// cap of string or slice
		naddr(n->left, a, canemitcode);
		if(a->type == D_CONST && a->offset == 0)
			break;	// cap(nil)
		a->etype = TUINT32;
		a->offset += Array_cap;
		a->width = 4;
		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
			checkoffset(a, canemitcode);
		break;

//	case OADD:
//		if(n->right->op == OLITERAL) {
//			v = n->right->vconst;
//			naddr(n->left, a, canemitcode);
//		} else
//		if(n->left->op == OLITERAL) {
//			v = n->left->vconst;
//			naddr(n->right, a, canemitcode);
//		} else
//			goto bad;
//		a->offset += v;
//		break;

	}
}

int
dotaddable(Node *n, Node *n1)
{
	int o, oary[10];
	Node *nn;

	if(n->op != ODOT)
		return 0;

	o = dotoffset(n, oary, &nn);
	if(nn != N && nn->addable && o == 1 && oary[0] >= 0) {
		*n1 = *nn;
		n1->type = n->type;
		n1->xoffset += oary[0];
		return 1;
	}
	return 0;
}

void
sudoclean(void)
{
}

int
sudoaddable(int as, Node *n, Addr *a)
{
	USED(as);
	USED(n);
	USED(a);

	return 0;
}