path: root/qbe.c

#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "util.h"
#include "cc.h"

struct value {
	enum {
		VALUE_NONE,
		VALUE_GLOBAL,
		VALUE_INTCONST,
		VALUE_FLTCONST,
		VALUE_DBLCONST,
		VALUE_TEMP,
		VALUE_TYPE,
		VALUE_LABEL,

		VALUE_THREAD = 1<<4,
	} kind;
	unsigned id;
	union {
		char *name;
		unsigned long long i;
		double f;
	} u;
};

struct lvalue {
	struct value *addr;
	struct bitfield bits;
};

enum instkind {
	INONE,

#define OP(op, name) op,
#include "ops.h"
#undef OP

	IARG,
	IVARARG,
};

struct qbetype {
	char base, data;
	enum instkind load, store;
};

struct inst {
	enum instkind kind;
	int class;
	struct value res, *arg[2];
};

struct jump {
	enum {
		JUMP_NONE,
		JUMP_JMP,
		JUMP_JNZ,
		JUMP_RET,
	} kind;
	struct value *arg;
	struct block *blk[2];
};

struct block {
	struct value label;
	struct array insts;
	struct {
		int class;
		struct block *blk[2];
		struct value *val[2];
		struct value res;
	} phi;
	struct jump jump;

	struct block *next;
};

struct switchcase {
	struct treenode node;
	struct block *body;
};

struct func {
	struct decl *decl, *namedecl;
	char *name;
	struct value *paramtemps;
	struct type *type;
	struct block *start, *end;
	struct map gotos;
	unsigned lastid;
};

static const int ptrclass = 'l';

void
switchcase(struct switchcases *cases, unsigned long long i, struct block *b)
{
	struct switchcase *c;

	c = treeinsert(&cases->root, i, sizeof(*c));
	if (!c->node.new)
		error(&tok.loc, "multiple 'case' labels with same value");
	c->body = b;
}

/* values */

struct block *
mkblock(char *name)
{
	static unsigned id;
	struct block *b;

	b = xmalloc(sizeof(*b));
	b->label.kind = VALUE_LABEL;
	b->label.u.name = name;
	b->label.id = ++id;
	b->insts = (struct array){0};
	b->jump.kind = JUMP_NONE;
	b->phi.res.kind = VALUE_NONE;
	b->next = NULL;

	return b;
}

struct value *
mkglobal(struct decl *d)
{
	static unsigned id;
	struct value *v;

	v = xmalloc(sizeof(*v));
	v->kind = VALUE_GLOBAL;
	if (d->kind == DECLOBJECT && d->u.obj.storage == SDTHREAD)
		v->kind |= VALUE_THREAD;
	if (d->asmname) {
		v->u.name = d->asmname;
		v->id = 0;
	} else {
		v->u.name = d->name;
		v->id = d->linkage == LINKNONE ? ++id : 0;
	}

	return v;
}

struct value *
mkintconst(unsigned long long n)
{
	struct value *v;

	v = xmalloc(sizeof(*v));
	v->kind = VALUE_INTCONST;
	v->u.i = n;

	return v;
}

unsigned long long
intconstvalue(struct value *v)
{
	assert(v->kind == VALUE_INTCONST);
	return v->u.i;
}

static struct value *
mkfltconst(int kind, double n)
{
	struct value *v;

	v = xmalloc(sizeof(*v));
	v->kind = kind;
	v->u.f = n;

	return v;
}

static struct qbetype
qbetype(struct type *t)
{
	static const struct qbetype
		ub = {'w', 'b', ILOADUB, ISTOREB},
		sb = {'w', 'b', ILOADSB, ISTOREB},
		uh = {'w', 'h', ILOADUH, ISTOREH},
		sh = {'w', 'h', ILOADSH, ISTOREH},
		w = {'w', 'w', ILOADW, ISTOREW},
		l = {'l', 'l', ILOADL, ISTOREL},
		s = {'s', 's', ILOADS, ISTORES},
		d = {'d', 'd', ILOADD, ISTORED},
		v = {0};

	if (t == &typevoid)
		return v;
	if (!(t->prop & PROPSCALAR))
		return l;
	switch (t->size) {
	case 1: return t->u.basic.issigned ? sb : ub;
	case 2: return t->u.basic.issigned ? sh : uh;
	case 4: return t->prop & PROPFLOAT ? s : w;
	case 8: return t->prop & PROPFLOAT ? d : l;
	case 16: fatal("long double is not yet supported");
	}
	assert(0);
}

/* functions */

static void emittype(struct type *);
static void emitname(struct value *);
static void emitvalue(struct value *);

static void
functemp(struct func *f, struct value *v)
{
	v->kind = VALUE_TEMP;
	v->u.name = NULL;
	v->id = ++f->lastid;
}

static const char *const instname[] = {
#define OP(op, name) [op] = name,
#include "ops.h"
#undef OP
};

static struct inst *
mkinst(struct func *f, int op, int class, struct value *arg0, struct value *arg1)
{
	struct inst *inst;

	inst = xmalloc(sizeof(*inst));
	inst->kind = op;
	inst->class = class;
	inst->arg[0] = arg0;
	inst->arg[1] = arg1;
	if (class && op != IARG)
		functemp(f, &inst->res);
	else
		inst->res.kind = VALUE_NONE;
	return inst;
}

static struct value *
funcinst(struct func *f, int op, int class, struct value *arg0, struct value *arg1)
{
	struct inst *inst;
	struct block *b;

	if (f->end->jump.kind) {
		b = mkblock("dead");
		funclabel(f, b);
	}
	inst = mkinst(f, op, class, arg0, arg1);
	arrayaddptr(&f->end->insts, inst);
	return &inst->res;
}

static void
funcalloc(struct func *f, struct decl *d)
{
	enum instkind op;
	struct inst *inst;
	unsigned long long size;
	int align;

	assert(!d->type->incomplete);
	assert(d->type->size > 0);
	size = d->type->size;
	align = d->u.obj.align;
	switch (align) {
	case 1:
	case 2:
	case 4:  op = IALLOC4; break;
	case 8:  op = IALLOC8; break;
	default: size += align - 16; /* fallthrough */
	case 16: op = IALLOC16; break;
	}
	inst = mkinst(f, op, ptrclass, mkintconst(size), NULL);
	arrayaddptr(&f->start->insts, inst);
	if (align > 16) {
		/* TODO: implement alloc32 in QBE and use that instead */
		inst = mkinst(f, IADD, ptrclass, &inst->res, mkintconst(align - 16));
		arrayaddptr(&f->start->insts, inst);
		inst = mkinst(f, IAND, ptrclass, &inst->res, mkintconst(-align));
		arrayaddptr(&f->start->insts, inst);
	}
	d->value = &inst->res;
}

static struct value *
funcbits(struct func *f, struct type *t, struct value *v, struct bitfield b)
{
	int class, bits;

	class = t->size <= 4 ? 'w' : 'l';
	bits = b.after;
	if (bits) {
		bits += (t->size + 3 & ~3) - t->size << 3;
		v = funcinst(f, ISHL, class, v, mkintconst(bits));
	}
	bits += b.before;
	if (bits)
		v = funcinst(f, t->u.basic.issigned ? ISAR : ISHR, class, v, mkintconst(bits));
	return v;
}

static void
funccopy(struct func *f, struct value *dst, struct value *src, unsigned long long size, int align)
{
	enum instkind load, store;
	int class;
	struct value *tmp, *inc;
	unsigned long long off;

	assert((align & align - 1) == 0);
	class = 'w';
	switch (align) {
	case 1: load = ILOADUB, store = ISTOREB; break;
	case 2: load = ILOADUH, store = ISTOREH; break;
	case 4: load = ILOADW, store = ISTOREW; break;
	default: load = ILOADL, store = ISTOREL, align = 8, class = 'l'; break;
	}
	inc = mkintconst(align);
	off = 0;
	for (;;) {
		tmp = funcinst(f, load, class, src, NULL);
		funcinst(f, store, 0, tmp, dst);
		off += align;
		if (off >= size)
			break;
		src = funcinst(f, IADD, ptrclass, src, inc);
		dst = funcinst(f, IADD, ptrclass, dst, inc);
	}
}

static struct value *
funcstore(struct func *f, struct type *t, enum typequal tq, struct lvalue lval, struct value *v)
{
	struct value *r;
	enum typeprop tp;
	unsigned long long mask;
	struct qbetype qt;
	int bits;

	if (tq & QUALVOLATILE)
		error(&tok.loc, "volatile store is not yet supported");
	if (tq & QUALCONST)
		error(&tok.loc, "cannot store to 'const' object");
	tp = t->prop;
	assert(!lval.bits.before && !lval.bits.after || tp & PROPINT);
	r = v;
	switch (t->kind) {
	case TYPESTRUCT:
	case TYPEUNION:
	case TYPEARRAY:
		funccopy(f, lval.addr, v, t->size, t->align);
		break;
	case TYPEPOINTER:
		t = &typeulong;
		/* fallthrough */
	default:
		assert(tp & PROPSCALAR);
		qt = qbetype(t);
		bits = lval.bits.before + lval.bits.after;
		if (bits) {
			mask = 0xffffffffffffffffu >> 64 - t->size * 8 + bits << lval.bits.before;
			v = funcinst(f, ISHL, qt.base, v, mkintconst(lval.bits.before));
			r = funcbits(f, t, v, lval.bits);
			v = funcinst(f, IAND, qt.base, v, mkintconst(mask));
			v = funcinst(f, IOR, qt.base, v,
				funcinst(f, IAND, qt.base,
					funcinst(f, qt.load, qt.base, lval.addr, NULL),
					mkintconst(~mask)
				)
			);
		}
		funcinst(f, qt.store, 0, v, lval.addr);
		break;
	}
	return r;
}

static struct value *
funcload(struct func *f, struct type *t, struct lvalue lval)
{
	struct value *v;
	struct qbetype qt;

	switch (t->kind) {
	case TYPESTRUCT:
	case TYPEUNION:
	case TYPEARRAY:
		return lval.addr;
	}
	qt = qbetype(t);
	v = funcinst(f, qt.load, qt.base, lval.addr, NULL);
	return funcbits(f, t, v, lval.bits);
}

static struct value *
convert(struct func *f, struct type *dst, struct type *src, struct value *l)
{
	enum instkind op;
	struct value *r = NULL;
	int class;

	if (src->kind == TYPEPOINTER)
		src = &typeulong;
	if (dst->kind == TYPEPOINTER)
		dst = &typeulong;
	if (dst->kind == TYPEVOID)
		return NULL;
	if (!(src->prop & PROPREAL) || !(dst->prop & PROPREAL))
		fatal("internal error; unsupported conversion");
	if (dst->kind == TYPEBOOL) {
		class = 'w';
		if (src->prop & PROPINT) {
			r = mkintconst(0);
			switch (src->size) {
			case 1: op = ICNEW, l = funcinst(f, IEXTUB, 'w', l, NULL); break;
			case 2: op = ICNEW, l = funcinst(f, IEXTUH, 'w', l, NULL); break;
			case 4: op = ICNEW; break;
			case 8: op = ICNEL; break;
			default:
				fatal("internal error; unknown integer conversion");
				return NULL;  /* unreachable */
			}
		} else {
			assert(src->prop & PROPFLOAT);
			switch (src->size) {
			case 4: op = ICNES, r = mkfltconst(VALUE_FLTCONST, 0); break;
			case 8: op = ICNED, r = mkfltconst(VALUE_DBLCONST, 0); break;
			default:
				fatal("internal error; unknown floating point conversion");
				return NULL;  /* unreachable */
			}
		}
	} else if (dst->prop & PROPINT) {
		class = dst->size == 8 ? 'l' : 'w';
		if (src->prop & PROPINT) {
			if (dst->size <= src->size)
				return l;
			switch (src->size) {
			case 4: op = src->u.basic.issigned ? IEXTSW : IEXTUW; break;
			case 2: op = src->u.basic.issigned ? IEXTSH : IEXTUH; break;
			case 1: op = src->u.basic.issigned ? IEXTSB : IEXTUB; break;
			default:
				fatal("internal error; unknown integer conversion");
				return NULL;  /* unreachable */
			}
		} else {
			if (dst->u.basic.issigned)
				op = src->size == 8 ? IDTOSI : ISTOSI;
			else
				op = src->size == 8 ? IDTOUI : ISTOUI;
		}
	} else {
		class = dst->size == 8 ? 'd' : 's';
		if (src->prop & PROPINT) {
			if (src->u.basic.issigned)
				op = src->size == 8 ? ISLTOF : ISWTOF;
			else
				op = src->size == 8 ? IULTOF : IUWTOF;
		} else {
			assert(src->prop & PROPFLOAT);
			if (src->size == dst->size)
				return l;
			op = src->size < dst->size ? IEXTS : ITRUNCD;
		}
	}

	return funcinst(f, op, class, l, r);
}

struct func *
mkfunc(struct decl *decl, char *name, struct type *t, struct scope *s)
{
	struct func *f;
	struct decl *d;
	struct value *v;

	f = xmalloc(sizeof(*f));
	f->decl = decl;
	f->name = name;
	f->type = t;
	f->start = f->end = mkblock("start");
	f->lastid = 0;
	mapinit(&f->gotos, 8);
	emittype(t->base);

	/* allocate space for parameters */
	f->paramtemps = xreallocarray(NULL, t->u.func.nparam, sizeof *f->paramtemps);
	for (d = t->u.func.params, v = f->paramtemps; d; d = d->next, ++v) {
		emittype(d->type);
		functemp(f, v);
		if(!d->name)
			continue;
		if (d->type->value) {
			d->value = v;
		} else {
			funcalloc(f, d);
			funcstore(f, d->type, QUALNONE, (struct lvalue){d->value}, v);
		}
	}

	t = mkarraytype(&typechar, QUALCONST, strlen(name) + 1);
	d = mkdecl("__func__", DECLOBJECT, t, QUALNONE, LINKNONE);
	d->u.obj.storage = SDSTATIC;
	d->value = mkglobal(d);
	scopeputdecl(s, d);
	f->namedecl = d;

	funclabel(f, mkblock("body"));

	return f;
}

void
delfunc(struct func *f)
{
	struct block *b;
	struct inst **inst;

	while (b = f->start) {
		f->start = b->next;
		arrayforeach (&b->insts, inst)
			free(*inst);
		free(b->insts.val);
		free(b);
	}
	mapfree(&f->gotos, free);
	free(f);
}

struct type *
functype(struct func *f)
{
	return f->type;
}

void
funclabel(struct func *f, struct block *b)
{
	f->end->next = b;
	f->end = b;
}

void
funcjmp(struct func *f, struct block *l)
{
	struct block *b = f->end;

	if (!b->jump.kind) {
		b->jump.kind = JUMP_JMP;
		b->jump.blk[0] = l;
	}
}

void
funcjnz(struct func *f, struct value *v, struct type *t, struct block *l1, struct block *l2)
{
	struct block *b = f->end;

	if (b->jump.kind)
		return;
	if (t) {
		assert(t->prop & PROPSCALAR);
		/*
		Ideally we would just do this conversion unconditionally,
		but QBE is not currently able to optimize the conversion
		away for int.
		*/
		if (t->prop & PROPINT && t->size < 4)
			v = convert(f, &typeint, t, v);
		else if (t->prop & PROPFLOAT || t->size > 4)
			v = convert(f, &typebool, t, v);
	}
	b->jump.kind = JUMP_JNZ;
	b->jump.arg = v;
	b->jump.blk[0] = l1;
	b->jump.blk[1] = l2;
}

void
funcret(struct func *f, struct value *v)
{
	struct block *b = f->end;

	if (!b->jump.kind) {
		b->jump.kind = JUMP_RET;
		b->jump.arg = v;
	}
}

struct gotolabel *
funcgoto(struct func *f, char *name)
{
	void **entry;
	struct gotolabel *g;
	struct mapkey key;

	mapkey(&key, name, strlen(name));
	entry = mapput(&f->gotos, &key);
	g = *entry;
	if (!g) {
		g = xmalloc(sizeof(*g));
		g->label = mkblock(name);
		*entry = g;
	}

	return g;
}

static struct lvalue
funclval(struct func *f, struct expr *e)
{
	struct lvalue lval = {0};
	struct decl *d;

	if (e->kind == EXPRBITFIELD) {
		lval.bits = e->u.bitfield.bits;
		e = e->base;
	}
	switch (e->kind) {
	case EXPRIDENT:
		d = e->u.ident.decl;
		if (d->kind != DECLOBJECT && d->kind != DECLFUNC)
			error(&tok.loc, "identifier is not an object or function");  /* XXX: fix location, var name */
		if (d == f->namedecl) {
			fputs("data ", stdout);
			emitname(d->value);
			printf(" = { b \"%s\", b 0 }\n", f->name);
			f->namedecl = NULL;
		}
		lval.addr = d->value;
		break;
	case EXPRSTRING:
		d = stringdecl(e);
		lval.addr = d->value;
		break;
	case EXPRCOMPOUND:
		d = e->u.compound.decl;
		funcinit(f, d, e->u.compound.init, true);
		lval.addr = d->value;
		break;
	case EXPRUNARY:
		if (e->op != TMUL)
			error(&tok.loc, "expression is not an object");
		lval.addr = funcexpr(f, e->base);
		break;
	default:
		if (e->type->kind != TYPESTRUCT && e->type->kind != TYPEUNION)
			error(&tok.loc, "expression is not an object");
		lval.addr = funcexpr(f, e);
	}
	return lval;
}

struct value *
funcexpr(struct func *f, struct expr *e)
{
	enum instkind op = INONE;
	struct decl *d;
	struct value *l, *r, *v, **argvals;
	struct lvalue lval;
	struct expr *arg;
	struct block *b[3];
	struct type *t, *functype;
	size_t i;

	switch (e->kind) {
	case EXPRIDENT:
		d = e->u.ident.decl;
		switch (d->kind) {
		case DECLOBJECT: return funcload(f, d->type, (struct lvalue){d->value});
		case DECLCONST:  return d->value;
		default:
			fatal("unimplemented declaration kind %d", d->kind);
		}
		break;
	case EXPRCONST:
		t = e->type;
		if (t->prop & PROPINT || t->kind == TYPEPOINTER)
			return mkintconst(e->u.constant.u);
		assert(t->prop & PROPFLOAT);
		return mkfltconst(t->size == 4 ? VALUE_FLTCONST : VALUE_DBLCONST, e->u.constant.f);
	case EXPRBITFIELD:
	case EXPRCOMPOUND:
		lval = funclval(f, e);
		return funcload(f, e->type, lval);
	case EXPRINCDEC:
		lval = funclval(f, e->base);
		l = funcload(f, e->base->type, lval);
		t = e->type;
		if (t->kind == TYPEPOINTER) {
			r = mkintconst(t->base->size);
		} else if (t->prop & PROPINT) {
			r = mkintconst(1);
		} else if (t->prop & PROPFLOAT) {
			r = mkfltconst(t->size == 4 ? VALUE_FLTCONST : VALUE_DBLCONST, 1);
		} else {
			fatal("not a scalar");
			return NULL;  /* unreachable */
		}
		v = funcinst(f, e->op == TINC ? IADD : ISUB, qbetype(t).base, l, r);
		v = funcstore(f, e->type, e->qual, lval, v);
		return e->u.incdec.post ? l : v;
	case EXPRCALL:
		argvals = xreallocarray(NULL, e->u.call.nargs, sizeof(argvals[0]));
		for (arg = e->u.call.args, i = 0; arg; arg = arg->next, ++i) {
			emittype(arg->type);
			argvals[i] = funcexpr(f, arg);
		}
		t = e->type;
		emittype(t);
		v = funcinst(f, ICALL, qbetype(t).base, funcexpr(f, e->base), t->value);
		functype = e->base->type->base;
		for (arg = e->u.call.args, i = 0; arg; arg = arg->next, ++i) {
			if (functype->u.func.isvararg && i == functype->u.func.nparam)
				funcinst(f, IVARARG, 0, NULL, NULL);
			t = arg->type;
			funcinst(f, IARG, qbetype(t).base, argvals[i], t->value);
		}
		/*
		if (functype->func.isnoreturn)
			funcret(f, NULL);
		*/
		return v;
	case EXPRUNARY:
		switch (e->op) {
		case TBAND:
			lval = funclval(f, e->base);
			return lval.addr;
		case TMUL:
			r = funcexpr(f, e->base);
			return funcload(f, e->type, (struct lvalue){r});
		case TSUB:
			r = funcexpr(f, e->base);
			return funcinst(f, INEG, qbetype(e->type).base, r, NULL);
		}
		fatal("internal error; unknown unary expression");
		break;
	case EXPRCAST:
		l = funcexpr(f, e->base);
		return convert(f, e->type, e->base->type, l);
	case EXPRBINARY:
		l = funcexpr(f, e->u.binary.l);
		if (e->op == TLOR || e->op == TLAND) {
			b[0] = mkblock("logic_right");
			b[1] = mkblock("logic_join");
			t = e->u.binary.l->type;
			if (e->op == TLOR) {
				funcjnz(f, l, t, b[1], b[0]);
				b[1]->phi.val[0] = mkintconst(1);
			} else {
				funcjnz(f, l, t, b[0], b[1]);
				b[1]->phi.val[0] = mkintconst(0);
			}
			b[1]->phi.blk[0] = f->end;
			funclabel(f, b[0]);
			r = funcexpr(f, e->u.binary.r);
			b[1]->phi.val[1] = convert(f, &typebool, e->u.binary.r->type, r);
			b[1]->phi.blk[1] = f->end;
			funclabel(f, b[1]);
			functemp(f, &b[1]->phi.res);
			b[1]->phi.class = 'w';
			return &b[1]->phi.res;
		}
		r = funcexpr(f, e->u.binary.r);
		t = e->u.binary.l->type;
		if (t->kind == TYPEPOINTER)
			t = &typeulong;
		switch (e->op) {
		case TMUL:
			op = IMUL;
			break;
		case TDIV:
			op = !(t->prop & PROPINT) || t->u.basic.issigned ? IDIV : IUDIV;
			break;
		case TMOD:
			op = t->u.basic.issigned ? IREM : IUREM;
			break;
		case TADD:
			op = IADD;
			break;
		case TSUB:
			op = ISUB;
			break;
		case TSHL:
			op = ISHL;
			break;
		case TSHR:
			op = t->u.basic.issigned ? ISAR : ISHR;
			break;
		case TBOR:
			op = IOR;
			break;
		case TBAND:
			op = IAND;
			break;
		case TXOR:
			op = IXOR;
			break;
		case TLESS:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICLTS : t->u.basic.issigned ? ICSLTW : ICULTW;
			else
				op = t->prop & PROPFLOAT ? ICLTD : t->u.basic.issigned ? ICSLTL : ICULTL;
			break;
		case TGREATER:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICGTS : t->u.basic.issigned ? ICSGTW : ICUGTW;
			else
				op = t->prop & PROPFLOAT ? ICGTD : t->u.basic.issigned ? ICSGTL : ICUGTL;
			break;
		case TLEQ:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICLES : t->u.basic.issigned ? ICSLEW : ICULEW;
			else
				op = t->prop & PROPFLOAT ? ICLED : t->u.basic.issigned ? ICSLEL : ICULEL;
			break;
		case TGEQ:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICGES : t->u.basic.issigned ? ICSGEW : ICUGEW;
			else
				op = t->prop & PROPFLOAT ? ICGED : t->u.basic.issigned ? ICSGEL : ICUGEL;
			break;
		case TEQL:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICEQS : ICEQW;
			else
				op = t->prop & PROPFLOAT ? ICEQD : ICEQL;
			break;
		case TNEQ:
			if (t->size <= 4)
				op = t->prop & PROPFLOAT ? ICNES : ICNEW;
			else
				op = t->prop & PROPFLOAT ? ICNED : ICNEL;
			break;
		}
		if (op == INONE)
			fatal("internal error; unimplemented binary expression");
		return funcinst(f, op, qbetype(e->type).base, l, r);
	case EXPRCOND:
		b[0] = mkblock("cond_true");
		b[1] = mkblock("cond_false");
		b[2] = mkblock("cond_join");

		v = funcexpr(f, e->base);
		funcjnz(f, v, e->base->type, b[0], b[1]);

		funclabel(f, b[0]);
		b[2]->phi.val[0] = funcexpr(f, e->u.cond.t);
		b[2]->phi.blk[0] = f->end;
		funcjmp(f, b[2]);

		funclabel(f, b[1]);
		b[2]->phi.val[1] = funcexpr(f, e->u.cond.f);
		b[2]->phi.blk[1] = f->end;

		funclabel(f, b[2]);
		if (e->type == &typevoid)
			return NULL;
		functemp(f, &b[2]->phi.res);
		b[2]->phi.class = qbetype(e->type).base;
		return &b[2]->phi.res;
	case EXPRASSIGN:
		r = funcexpr(f, e->u.assign.r);
		if (e->u.assign.l->kind == EXPRTEMP) {
			e->u.assign.l->u.temp = r;
		} else {
			lval = funclval(f, e->u.assign.l);
			r = funcstore(f, e->u.assign.l->type, e->u.assign.l->qual, lval, r);
		}
		return r;
	case EXPRCOMMA:
		for (e = e->base; e->next; e = e->next)
			funcexpr(f, e);
		return funcexpr(f, e);
	case EXPRBUILTIN:
		switch (e->u.builtin.kind) {
		case BUILTINVASTART:
			l = funcexpr(f, e->base);
			funcinst(f, IVASTART, 0, l, NULL);
			break;
		case BUILTINVAARG:
			/* https://todo.sr.ht/~mcf/cproc/52 */
			if (!(e->type->prop & PROPSCALAR))
				error(&tok.loc, "va_arg with non-scalar type is not yet supported");
			l = funcexpr(f, e->base);
			return funcinst(f, IVAARG, qbetype(e->type).base, l, NULL);
		case BUILTINALLOCA:
			l = funcexpr(f, e->base);
			return funcinst(f, IALLOC16, ptrclass, l, NULL);
		case BUILTINUNREACHABLE:
			return NULL;
		default:
			fatal("internal error: unimplemented builtin");
		}
		return NULL;
	case EXPRTEMP:
		assert(e->u.temp);
		return e->u.temp;
	}
	fatal("unimplemented expression %d", e->kind);
	return NULL;
}

static void
zero(struct func *func, struct value *addr, int align, unsigned long long offset, unsigned long long end)
{
	static const enum instkind store[] = {
		[1] = ISTOREB,
		[2] = ISTOREH,
		[4] = ISTOREW,
		[8] = ISTOREL,
	};
	static struct value z = {.kind = VALUE_INTCONST};
	struct value *tmp;
	int a = 1;

	while (offset < end) {
		if ((align - (offset & align - 1)) & a) {
			tmp = offset ? funcinst(func, IADD, ptrclass, addr, mkintconst(offset)) : addr;
			funcinst(func, store[a], 0, &z, tmp);
			offset += a;
		}
		if (a < align)
			a <<= 1;
	}
}

void
funcinit(struct func *func, struct decl *d, struct init *init, bool hasinit)
{
	struct lvalue dst;
	struct value *src, *v;
	unsigned long long offset = 0, max = 0;
	size_t i, w;

	funcalloc(func, d);
	if (!hasinit)
		return;
	for (; init; init = init->next) {
		zero(func, d->value, d->type->align, offset, init->start);
		dst.bits = init->bits;
		if (init->expr->kind == EXPRSTRING) {
			w = init->expr->type->base->size;
			for (i = 0; i < init->expr->u.string.size && i * w < init->end - init->start; ++i) {
				v = mkintconst(init->start + i * w);
				dst.addr = funcinst(func, IADD, ptrclass, d->value, v);
				switch (w) {
				case 1: v = mkintconst(((unsigned char *)init->expr->u.string.data)[i]); break;
				case 2: v = mkintconst(((uint_least16_t *)init->expr->u.string.data)[i]); break;
				case 4: v = mkintconst(((uint_least32_t *)init->expr->u.string.data)[i]); break;
				}
				funcstore(func, init->expr->type->base, QUALNONE, dst, v);
			}
			offset = init->start + i * w;
		} else {
			if (offset < init->end && (dst.bits.before || dst.bits.after))
				zero(func, d->value, d->type->align, offset, init->end);
			dst.addr = d->value;
			/*
			QBE's memopt does not eliminate the store for ptr + 0,
			so only emit the add if the offset is non-zero
			*/
			if (init->start > 0)
				dst.addr = funcinst(func, IADD, ptrclass, dst.addr, mkintconst(init->start));
			src = funcexpr(func, init->expr);
			funcstore(func, init->expr->type, QUALNONE, dst, src);
			offset = init->end;
		}
		if (max < offset)
			max = offset;
	}
	zero(func, d->value, d->type->align, max, d->type->size);
}

static void
casesearch(struct func *f, int class, struct value *v, struct switchcase *c, struct block *defaultlabel)
{
	struct value *res, *key;
	struct block *label[3];

	if (!c) {
		funcjmp(f, defaultlabel);
		return;
	}
	label[0] = mkblock("switch_ne");
	label[1] = mkblock("switch_lt");
	label[2] = mkblock("switch_gt");

	/* XXX: linear search if c->node.height < 4 */
	key = mkintconst(c->node.key);
	res = funcinst(f, class == 'w' ? ICEQW : ICEQL, 'w', v, key);
	funcjnz(f, res, NULL, c->body, label[0]);
	funclabel(f, label[0]);
	res = funcinst(f, class == 'w' ? ICULTW : ICULTL, 'w', v, key);
	funcjnz(f, res, NULL, label[1], label[2]);
	funclabel(f, label[1]);
	casesearch(f, class, v, c->node.child[0], defaultlabel);
	funclabel(f, label[2]);
	casesearch(f, class, v, c->node.child[1], defaultlabel);
}

void
funcswitch(struct func *f, struct value *v, struct switchcases *c, struct block *defaultlabel)
{
	casesearch(f, qbetype(c->type).base, v, c->root, defaultlabel);
}

/* emit */

static void
emitname(struct value *v)
{
	static const char sigil[] = {
		[VALUE_TEMP] = '%',
		[VALUE_GLOBAL] = '$',
		[VALUE_TYPE] = ':',
		[VALUE_LABEL] = '@',
	};
	int kind;

	kind = v->kind & 0xf;
	if (kind >= LEN(sigil) || !sigil[kind])
		fatal("invalid value");
	putchar(sigil[kind]);
	if (kind == VALUE_GLOBAL && v->id)
		fputs(".L", stdout);
	if (v->u.name)
		fputs(v->u.name, stdout);
	if (v->id)
		printf(".%u", v->id);
}

static void
emitvalue(struct value *v)
{
	switch (v->kind & 0xf) {
	case VALUE_INTCONST:
		printf("%llu", v->u.i);
		break;
	case VALUE_FLTCONST:
		printf("s_%.17g", v->u.f);
		break;
	case VALUE_DBLCONST:
		printf("d_%.17g", v->u.f);
		break;
	case VALUE_GLOBAL:
		if (v->kind & VALUE_THREAD)
			fputs("thread ", stdout);
		/* fallthrough */
	default:
		emitname(v);
		break;
	}
}

static void
emitclass(int class, struct value *v)
{
	if (v && v->kind == VALUE_TYPE)
		emitname(v);
	else if (class)
		putchar(class);
	else
		fatal("type has no QBE representation");
}

/* XXX: need to consider _Alignas on struct members */
static void
emittype(struct type *t)
{
	static unsigned id;
	struct member *m, *other;
	struct type *sub;
	unsigned long long off;

	if (t->value || t->kind != TYPESTRUCT && t->kind != TYPEUNION)
		return;
	t->value = xmalloc(sizeof(*t->value));
	t->value->kind = VALUE_TYPE;
	t->value->u.name = t->u.structunion.tag;
	t->value->id = ++id;
	for (m = t->u.structunion.members; m; m = m->next) {
		for (sub = m->type; sub->kind == TYPEARRAY; sub = sub->base)
			;
		emittype(sub);
	}
	fputs("type ", stdout);
	emitname(t->value);
	if (t == targ->typevalist) {
		printf(" = align %d { %llu }\n", t->align, t->size);
		return;
	}
	fputs(" = { ", stdout);
	for (m = t->u.structunion.members, off = 0; m;) {
		if (t->kind == TYPESTRUCT) {
			/* look for a subsequent member with a larger storage unit */
			for (other = m->next; other; other = other->next) {
				if (other->offset >= ALIGNUP(m->offset + 1, 8))
					break;
				if (other->offset <= m->offset)
					m = other;
			}
			off = m->offset + m->type->size;
		} else {
			fputs("{ ", stdout);
		}
		for (sub = m->type; sub->kind == TYPEARRAY; sub = sub->base)
			;
		emitclass(qbetype(sub).data, sub->value);
		if (m->type->size > sub->size)
			printf(" %llu", m->type->size / sub->size);
		if (t->kind == TYPESTRUCT) {
			fputs(", ", stdout);
			/* skip subsequent members contained within the same storage unit */
			do m = m->next;
			while (m && m->offset < off);
		} else {
			fputs(" } ", stdout);
			m = m->next;
		}
	}
	puts("}");
}

static struct inst **
emitinst(struct inst **instp, struct inst **instend)
{
	int op, first;
	struct inst *inst = *instp;

	putchar('\t');
	assert(inst->kind < LEN(instname));
	if (inst->res.kind) {
		emitvalue(&inst->res);
		fputs(" =", stdout);
		emitclass(inst->class, inst->arg[1]);
		putchar(' ');
	}
	fputs(instname[inst->kind], stdout);
	putchar(' ');
	emitvalue(inst->arg[0]);
	++instp;
	op = inst->kind;
	switch (op) {
	case ICALL:
		putchar('(');
		for (first = 1; instp != instend; ++instp) {
			inst = *instp;
			if (inst->kind == IVARARG) {
				fputs(", ...", stdout);
				continue;
			}
			if (inst->kind != IARG)
				break;
			if (first)
				first = 0;
			else
				fputs(", ", stdout);
			emitclass(inst->class, inst->arg[1]);
			putchar(' ');
			emitvalue(inst->arg[0]);
		}
		putchar(')');
		break;
	default:
		if (inst->arg[1]) {
			fputs(", ", stdout);
			emitvalue(inst->arg[1]);
		}
	}
	putchar('\n');
	return instp;
}

static void
emitjump(struct jump *j)
{
	switch (j->kind) {
	case JUMP_RET:
		fputs("\tret", stdout);
		if (j->arg) {
			fputc(' ', stdout);
			emitvalue(j->arg);
		}
		putchar('\n');
		break;
	case JUMP_JMP:
		fputs("\tjmp ", stdout);
		emitname(&j->blk[0]->label);
		putchar('\n');
		break;
	case JUMP_JNZ:
		fputs("\tjnz ", stdout);
		emitvalue(j->arg);
		fputs(", ", stdout);
		emitname(&j->blk[0]->label);
		fputs(", ", stdout);
		emitname(&j->blk[1]->label);
		putchar('\n');
		break;
	}
}

void
emitfunc(struct func *f, bool global)
{
	struct block *b;
	struct inst **inst, **instend;
	struct decl *p;
	struct value *v;

	if (f->end->jump.kind == JUMP_NONE) {
		v = NULL;
		/* implicitly return 0 from main if we reach the end of the function */
		if (strcmp(f->name, "main") == 0 && f->type->base == &typeint)
			v = mkintconst(0);
		funcret(f, v);
	}
	if (global)
		puts("export");
	fputs("function ", stdout);
	if (f->type->base != &typevoid) {
		emitclass(qbetype(f->type->base).base, f->type->base->value);
		putchar(' ');
	}
	emitname(f->decl->value);
	putchar('(');
	for (p = f->type->u.func.params, v = f->paramtemps; p; p = p->next, ++v) {
		if (p != f->type->u.func.params)
			fputs(", ", stdout);
		emitclass(qbetype(p->type).base, p->type->value);
		putchar(' ');
		emitname(v);
	}
	if (f->type->u.func.isvararg) {
		if (f->type->u.func.params)
			fputs(", ", stdout);
		fputs("...", stdout);
	}
	puts(") {");
	for (b = f->start; b; b = b->next) {
		emitname(&b->label);
		putchar('\n');
		if (b->phi.res.kind) {
			putchar('\t');
			emitvalue(&b->phi.res);
			printf(" =%c phi ", b->phi.class);
			emitname(&b->phi.blk[0]->label);
			putchar(' ');
			emitvalue(b->phi.val[0]);
			fputs(", ", stdout);
			emitname(&b->phi.blk[1]->label);
			putchar(' ');
			emitvalue(b->phi.val[1]);
			putchar('\n');
		}
		instend = (struct inst **)((char *)b->insts.val + b->insts.len);
		for (inst = b->insts.val; inst != instend;)
			inst = emitinst(inst, instend);
		emitjump(&b->jump);
	}
	puts("}");
}

static void
dataitem(struct expr *expr, unsigned long long size)
{
	struct decl *decl;
	size_t i, w;
	unsigned c;

	switch (expr->kind) {
	case EXPRUNARY:
		if (expr->op != TBAND)
			fatal("not a address expr");
		expr = expr->base;
		if (expr->kind != EXPRIDENT)
			error(&tok.loc, "initializer is not a constant expression");
		decl = expr->u.ident.decl;
		if (decl->kind == DECLOBJECT && decl->u.obj.storage != SDSTATIC)
			error(&tok.loc, "initializer is not a constant expression");
		emitname(decl->value);
		break;
	case EXPRBINARY:
		if (expr->op != TADD || expr->u.binary.l->kind != EXPRUNARY || expr->u.binary.r->kind != EXPRCONST)
			error(&tok.loc, "initializer is not a constant expression");
		dataitem(expr->u.binary.l, 0);
		fputs(" + ", stdout);
		dataitem(expr->u.binary.r, 0);
		break;
	case EXPRCONST:
		if (expr->type->prop & PROPFLOAT)
			printf("%c_%.17g", expr->type->size == 4 ? 's' : 'd', expr->u.constant.f);
		else
			printf("%llu", expr->u.constant.u);
		break;
	case EXPRSTRING:
		w = expr->type->base->size;
		if (w == 1) {
			fputc('"', stdout);
			for (i = 0; i < expr->u.string.size && i < size; ++i) {
				c = ((unsigned char *)expr->u.string.data)[i];
				if (isprint(c) && c != '"' && c != '\\')
					putchar(c);
				else
					printf("\\%03o", c);
			}
			fputc('"', stdout);
		} else {
			for (i = 0; i < expr->u.string.size && i * w < size; ++i) {
				switch (w) {
				case 2: printf("%" PRIuLEAST16 " ", ((uint_least16_t *)expr->u.string.data)[i]); break;
				case 4: printf("%" PRIuLEAST32 " ", ((uint_least32_t *)expr->u.string.data)[i]); break;
				default: assert(0);
				}
			}
		}
		if (i * w < size)
			printf(", z %llu", size - (unsigned long long)i * w);
		break;
	default:
		error(&tok.loc, "initializer is not a constant expression");
	}
}

void
emitdata(struct decl *d, struct init *init)
{
	struct init *cur;
	struct type *t;
	unsigned long long offset = 0, start, end, bits = 0;
	size_t i;
	int align;

	align = d->u.obj.align;
	for (cur = init; cur; cur = cur->next)
		cur->expr = eval(cur->expr);
	if (d->u.obj.storage == SDTHREAD)
		fputs("thread ", stdout);
	if (d->linkage == LINKEXTERN)
		fputs("export ", stdout);
	fputs("data ", stdout);
	emitname(d->value);
	printf(" = align %d { ", align);

	while (init) {
		cur = init;
		while ((init = init->next) && init->start * 8 + init->bits.before < cur->end * 8 - cur->bits.after) {
			/*
			XXX: Currently, if multiple union members are
			initialized, these assertions may not hold.
			(https://todo.sr.ht/~mcf/cproc/38)
			*/
			assert(cur->expr->kind == EXPRSTRING);
			assert(init->expr->kind == EXPRCONST);
			i = (init->start - cur->start) / cur->expr->type->base->size;
			switch (cur->expr->type->base->size) {
			case 1: ((unsigned char *)cur->expr->u.string.data)[i]  = init->expr->u.constant.u; break;
			case 2: ((uint_least16_t *)cur->expr->u.string.data)[i] = init->expr->u.constant.u; break;
			case 4: ((uint_least32_t *)cur->expr->u.string.data)[i] = init->expr->u.constant.u; break;
			}
		}
		start = cur->start + cur->bits.before / 8;
		end = cur->end - (cur->bits.after + 7) / 8;
		if (offset < start && bits) {
			printf("b %u, ", (unsigned)bits);  /* unfinished byte from previous bit-field */
			++offset;
			bits = 0;
		}
		if (offset < start)
			printf("z %llu, ", start - offset);
		if (cur->bits.before || cur->bits.after) {
			/* little-endian target specific */
			assert(cur->expr->type->prop & PROPINT);
			assert(cur->expr->kind == EXPRCONST);
			bits |= cur->expr->u.constant.u << cur->bits.before % 8;
			for (offset = start; offset < end; ++offset, bits >>= 8)
				printf("b %u, ", (unsigned)bits & 0xff);
			/*
			clear the upper `after` bits in the last byte,
			or all bits when `after` is 0 (we ended on a
			byte boundary).
			*/
			bits &= 0x7f >> (cur->bits.after + 7) % 8;
		} else {
			t = cur->expr->type;
			if (t->kind == TYPEARRAY)
				t = t->base;
			printf("%c ", qbetype(t).data);
			dataitem(cur->expr, cur->end - cur->start);
			fputs(", ", stdout);
		}
		offset = end;
	}
	if (bits) {
		printf("b %u, ", (unsigned)bits);
		++offset;
	}
	assert(offset <= d->type->size);
	if (offset < d->type->size)
		printf("z %llu ", d->type->size - offset);
	puts("}");
}