add rv64 backend

It is mostly complete, but still has a few ABI bugs when passing
floats in structs, or when structs are passed partly in register,
and partly on stack.

1 files changed, 584 insertions, 0 deletions

diff --git a/rv64/abi.c b/rv64/abi.c
new file mode 100644
index 0000000..1dd4fb0
--- /dev/null
+++ b/rv64/abi.c
@@ -0,0 +1,584 @@
+#include "all.h"
+
+typedef struct Class Class;
+typedef struct Insl Insl;
+typedef struct Params Params;
+
+enum {
+	Cptr  = 1, /* replaced by a pointer */
+	Cstk1 = 2, /* pass first XLEN on the stack */
+	Cstk2 = 4, /* pass second XLEN on the stack */
+	Cstk = Cstk1 | Cstk2,
+	Cfpint = 8, /* float passed like integer */
+};
+
+struct Class {
+	char class;
+	uint size;
+	Typ *t;
+	uchar nreg;
+	uchar ngp;
+	uchar nfp;
+	int reg[2];
+	int cls[2];
+};
+
+struct Insl {
+	Ins i;
+	Insl *link;
+};
+
+struct Params {
+	int ngp;
+	int nfp;
+	int stk; /* stack offset for varargs */
+};
+
+static int gpreg[] = { A0,  A1,  A2,  A3,  A4,  A5,  A6,  A7};
+static int fpreg[] = {FA0, FA1, FA2, FA3, FA4, FA5, FA6, FA7};
+
+/* layout of call's second argument (RCall)
+ *
+ *  29       8    4  2  0
+ *  |0.00|xxxx|xxxx|xx|xx|                  range
+ *           |    |  |  ` gp regs returned (0..2)
+ *           |    |  ` fp regs returned    (0..2)
+ *           |    ` gp regs passed         (0..8)
+ *            ` fp regs passed             (0..8)
+ */
+
+bits
+rv64_retregs(Ref r, int p[2])
+{
+	bits b;
+	int ngp, nfp;
+
+	assert(rtype(r) == RCall);
+	ngp = r.val & 3;
+	nfp = (r.val >> 2) & 3;
+	if (p) {
+		p[0] = ngp;
+		p[1] = nfp;
+	}
+	b = 0;
+	while (ngp--)
+		b |= BIT(A0+ngp);
+	while (nfp--)
+		b |= BIT(FA0+nfp);
+	return b;
+}
+
+bits
+rv64_argregs(Ref r, int p[2])
+{
+	bits b;
+	int ngp, nfp;
+
+	assert(rtype(r) == RCall);
+	ngp = (r.val >> 4) & 15;
+	nfp = (r.val >> 8) & 15;
+	b = 0;
+	if (p) {
+		p[0] = ngp;
+		p[1] = nfp;
+	}
+	b = 0;
+	while (ngp--)
+		b |= BIT(A0+ngp);
+	while (nfp--)
+		b |= BIT(FA0+nfp);
+	return b;
+}
+
+static void
+typclass(Class *c, Typ *t, int *gp, int *fp)
+{
+	uint64_t sz;
+	uint n;
+
+	sz = (t->size + 7) & ~7;
+	c->t = t;
+	c->class = 0;
+	c->ngp = 0;
+	c->nfp = 0;
+
+	if (t->align > 4)
+		err("alignments larger than 16 are not supported");
+
+	if (t->dark || sz > 16 || sz == 0) {
+		/* large structs are replaced by a
+		 * pointer to some caller-allocated
+		 * memory */
+		c->class |= Cptr;
+		c->size = 8;
+		return;
+	}
+
+	c->size = sz;
+
+	/* TODO: float */
+
+	for (n=0; n<sz/8; n++, c->ngp++) {
+		c->reg[n] = *gp++;
+		c->cls[n] = Kl;
+	}
+
+	c->nreg = n;
+}
+
+static void
+sttmps(Ref tmp[], int cls[], uint nreg, Ref mem, Fn *fn)
+{
+	static int st[] = {
+		[Kw] = Ostorew, [Kl] = Ostorel,
+		[Ks] = Ostores, [Kd] = Ostored
+	};
+	uint n;
+	uint64_t off;
+	Ref r;
+
+	assert(nreg <= 4);
+	off = 0;
+	for (n=0; n<nreg; n++) {
+		tmp[n] = newtmp("abi", cls[n], fn);
+		r = newtmp("abi", Kl, fn);
+		emit(st[cls[n]], 0, R, tmp[n], r);
+		emit(Oadd, Kl, r, mem, getcon(off, fn));
+		off += KWIDE(cls[n]) ? 8 : 4;
+	}
+}
+
+static void
+ldregs(int reg[], int cls[], int n, Ref mem, Fn *fn)
+{
+	int i;
+	uint64_t off;
+	Ref r;
+
+	off = 0;
+	for (i=0; i<n; i++) {
+		r = newtmp("abi", Kl, fn);
+		emit(Oload, cls[i], TMP(reg[i]), r, R);
+		emit(Oadd, Kl, r, mem, getcon(off, fn));
+		off += KWIDE(cls[i]) ? 8 : 4;
+	}
+}
+
+static void
+selret(Blk *b, Fn *fn)
+{
+	int j, k, cty;
+	Ref r;
+	Class cr;
+
+	j = b->jmp.type;
+
+	if (!isret(j) || j == Jret0)
+		return;
+
+	r = b->jmp.arg;
+	b->jmp.type = Jret0;
+
+	if (j == Jretc) {
+		typclass(&cr, &typ[fn->retty], gpreg, fpreg);
+		cty = (cr.nfp << 2) | cr.ngp;
+		if (cr.class & Cptr) {
+			assert(rtype(fn->retr) == RTmp);
+			blit(fn->retr, 0, r, cr.t->size, fn);
+		} else {
+			ldregs(cr.reg, cr.cls, cr.nreg, r, fn);
+		}
+	} else {
+		k = j - Jretw;
+		if (KBASE(k) == 0) {
+			emit(Ocopy, k, TMP(A0), r, R);
+			cty = 1;
+		} else {
+			emit(Ocopy, k, TMP(FA0), r, R);
+			cty = 1 << 2;
+		}
+	}
+
+	b->jmp.arg = CALL(cty);
+}
+
+static int
+argsclass(Ins *i0, Ins *i1, Class *carg, Ref *env, int retptr)
+{
+	int ngp, nfp, *gp, *fp, vararg;
+	Class *c;
+	Ins *i;
+
+	gp = gpreg;
+	fp = fpreg;
+	ngp = 8;
+	nfp = 8;
+	vararg = 0;
+	if (retptr) {
+		gp++;
+		ngp--;
+	}
+	for (i=i0, c=carg; i<i1; i++, c++) {
+		switch (i->op) {
+		case Opar:
+		case Oarg:
+			c->cls[0] = i->cls;
+			c->size = 8;
+			/* variadic float args are passed in int regs */
+			if (!vararg && KBASE(i->cls) == 1 && nfp > 0) {
+				nfp--;
+				c->reg[0] = *fp++;
+			} else if (ngp > 0) {
+				if (KBASE(i->cls) == 1)
+					c->class |= Cfpint;
+				ngp--;
+				c->reg[0] = *gp++;
+			} else {
+				c->class |= Cstk1;
+			}
+			break;
+		case Oargv:
+			/* subsequent arguments are variadic */
+			vararg = 1;
+			break;
+		case Oparc:
+		case Oargc:
+			typclass(c, &typ[i->arg[0].val], gp, fp);
+			if (c->class & Cptr) {
+				c->ngp = 1;
+				c->reg[0] = *gp;
+				c->cls[0] = Kl;
+			}
+			if (c->ngp <= ngp && c->nfp <= nfp) {
+				ngp -= c->ngp;
+				nfp -= c->nfp;
+				gp += c->ngp;
+				fp += c->nfp;
+				break;
+			}
+			c->ngp += c->nfp;
+			c->nfp = 0;
+			if (c->ngp <= ngp) {
+				ngp -= c->ngp;
+				gp += c->ngp;
+				break;
+			}
+			c->class |= Cstk1;
+			if (c->ngp - 1 > ngp)
+				c->class |= Cstk2;
+			break;
+		case Opare:
+			*env = i->to;
+			break;
+		case Oarge:
+			*env = i->arg[0];
+			break;
+		}
+	}
+	return (gp-gpreg) << 4 | (fp-fpreg) << 8;
+}
+
+static void
+stkblob(Ref r, Class *c, Fn *fn, Insl **ilp)
+{
+	Insl *il;
+	int al;
+	uint64_t sz;
+
+	il = alloc(sizeof *il);
+	al = c->t->align - 2; /* NAlign == 3 */
+	if (al < 0)
+		al = 0;
+	sz = c->class & Cptr ? c->t->size : c->size;
+	il->i = (Ins){Oalloc+al, Kl, r, {getcon(sz, fn)}};
+	il->link = *ilp;
+	*ilp = il;
+}
+
+static void
+selcall(Fn *fn, Ins *i0, Ins *i1, Insl **ilp)
+{
+	Ins *i;
+	Class *ca, *c, cr;
+	int k, cty, envc;
+	uint n;
+	uint64_t stk, off;
+	Ref r, r1, env, tmp[2];
+
+	env = R;
+	ca = alloc((i1-i0) * sizeof ca[0]);
+	cr.class = 0;
+
+	if (!req(i1->arg[1], R))
+		typclass(&cr, &typ[i1->arg[1].val], gpreg, fpreg);
+
+	cty = argsclass(i0, i1, ca, &env, cr.class & Cptr);
+	stk = 0;
+	for (i=i0, c=ca; i<i1; i++, c++) {
+		if (i->op == Oargv)
+			continue;
+		if (c->class & Cptr) {
+			i->arg[0] = newtmp("abi", Kl, fn);
+			stkblob(i->arg[0], c, fn, ilp);
+			i->op = Oarg;
+		}
+		if (c->class & Cstk1)
+			stk += 8;
+		if (c->class & Cstk2)
+			stk += 8;
+	}
+	if (stk)
+		emit(Osalloc, Kl, R, getcon(-stk, fn), R);
+
+	if (!req(i1->arg[1], R)) {
+		stkblob(i1->to, &cr, fn, ilp);
+		cty |= (cr.nfp << 2) | cr.ngp;
+		if (cr.class & Cptr) {
+			cty |= 1;
+			emit(Ocopy, Kw, R, TMP(A0), R);
+		} else {
+			sttmps(tmp, cr.cls, cr.nreg, i1->to, fn);
+			for (n=0; n<cr.nreg; n++) {
+				r = TMP(cr.reg[n]);
+				emit(Ocopy, cr.cls[n], tmp[n], r, R);
+			}
+		}
+	} else if (KBASE(i1->cls) == 0) {
+		emit(Ocopy, i1->cls, i1->to, TMP(A0), R);
+		cty |= 1;
+	} else {
+		emit(Ocopy, i1->cls, i1->to, TMP(FA0), R);
+		cty |= 1 << 2;
+	}
+
+	envc = !req(R, env);
+	if (envc)
+		die("todo (rv64 abi): env calls");
+	emit(Ocall, 0, R, i1->arg[0], CALL(cty));
+
+	if (cr.class & Cptr)
+		/* struct return argument */
+		emit(Ocopy, Kl, TMP(A0), i1->to, R);
+
+	/* move arguments into registers */
+	for (i=i0, c=ca; i<i1; i++, c++) {
+		if (i->op == Oargv || c->class & Cstk1)
+			continue;
+		if (i->op == Oargc) {
+			ldregs(c->reg, c->cls, c->nreg, i->arg[1], fn);
+		} else if (c->class & Cfpint) {
+			k = KWIDE(*c->cls) ? Kl : Kw;
+			r = newtmp("abi", k, fn);
+			emit(Ocopy, k, TMP(c->reg[0]), r, R);
+			c->reg[0] = r.val;
+		} else {
+			emit(Ocopy, *c->cls, TMP(*c->reg), i->arg[0], R);
+		}
+	}
+
+	for (i=i0, c=ca; i<i1; i++, c++) {
+		if (c->class & Cfpint)
+			emit(Ocast, KWIDE(*c->cls) ? Kl : Kw, TMP(*c->reg), i->arg[0], R);
+		if (c->class & Cptr)
+			blit(i->arg[0], 0, i->arg[1], c->t->size, fn);
+	}
+
+	if (!stk)
+		return;
+
+	r = newtmp("abi", Kl, fn);
+	for (i=i0, c=ca, off=0; i<i1; i++, c++) {
+		if (i->op == Oargv || (c->class & Cstk) == 0)
+			continue;
+		if (i->op != Oargc) {
+			r1 = newtmp("abi", Kl, fn);
+			/* w arguments are stored sign-extended
+			 * to 64-bits
+			 *
+			 * s arguments can just be stored with
+			 * Ostores into the first 32-bits in the
+			 * stack position since the ABI says the
+			 * upper bits are undefined
+			 */
+			emit(i->cls == Kw ? Ostorel : Ostorew+i->cls, 0, R, i->arg[0], r1);
+			if (i->cls == Kw) {
+				/* TODO: we only need this sign extension
+				 * for subtyped l temporaries passed as w
+				 * arguments (see rv64/isel.c:fixarg)
+				 *
+				 * however, we cannot just fix it in isel
+				 * since by that point we have forgotten
+				 * the original argument type
+				 */
+				curi->arg[0] = newtmp("abi", Kl, fn);
+				emit(Oextsw, Kl, curi->arg[0], i->arg[0], R);
+			}
+			emit(Oadd, Kl, r1, r, getcon(off, fn));
+		} else
+			blit(r, off, i->arg[1], c->t->size, fn);
+		off += c->size;
+	}
+	emit(Osalloc, Kl, r, getcon(stk, fn), R);
+}
+
+static Params
+selpar(Fn *fn, Ins *i0, Ins *i1)
+{
+	Class *ca, *c, cr;
+	Insl *il;
+	Ins *i;
+	int n, s, cty;
+	Ref r, env, tmp[16], *t;
+
+	env = R;
+	ca = alloc((i1-i0) * sizeof ca[0]);
+	cr.class = 0;
+	curi = &insb[NIns];
+
+	if (fn->retty >= 0) {
+		typclass(&cr, &typ[fn->retty], gpreg, fpreg);
+		if (cr.class & Cptr) {
+			fn->retr = newtmp("abi", Kl, fn);
+			emit(Ocopy, Kl, fn->retr, TMP(A0), R);
+		}
+	}
+
+	cty = argsclass(i0, i1, ca, &env, cr.class & Cptr);
+	fn->reg = rv64_argregs(CALL(cty), 0);
+
+	il = 0;
+	t = tmp;
+	for (i=i0, c=ca; i<i1; i++, c++) {
+		if (i->op != Oparc || (c->class & (Cptr|Cstk)))
+			continue;
+		sttmps(t, c->cls, c->nreg, i->to, fn);
+		stkblob(i->to, c, fn, &il);
+		t += c->nreg;
+	}
+	for (; il; il=il->link)
+		emiti(il->i);
+
+	t = tmp;
+	for (i=i0, c=ca, s=2 + 8 * fn->vararg; i<i1; i++, c++) {
+		if (i->op == Oparc
+		&& (c->class & Cptr) == 0) {
+			if (c->class & Cstk) {
+				fn->tmp[i->to.val].slot = -s;
+				s += c->size / 8;
+			} else {
+				for (n=0; n<c->nreg; n++) {
+					r = TMP(c->reg[n]);
+					emit(Ocopy, c->cls[n], *t++, r, R);
+				}
+			}
+		} else if (c->class & Cstk1) {
+			emit(Oload, c->cls[0], i->to, SLOT(-s), R);
+			s++;
+		} else {
+			emit(Ocopy, c->cls[0], i->to, TMP(c->reg[0]), R);
+		}
+	}
+
+	if (!req(R, env))
+		die("todo (rv64 abi): env calls");
+
+	return (Params){
+		.stk = s,
+		.ngp = (cty >> 4) & 15,
+		.nfp = (cty >> 8) & 15,
+	};
+}
+
+static void
+selvaarg(Fn *fn, Ins *i)
+{
+	Ref loc, newloc;
+
+	loc = newtmp("abi", Kl, fn);
+	newloc = newtmp("abi", Kl, fn);
+	emit(Ostorel, Kw, R, newloc, i->arg[0]);
+	emit(Oadd, Kl, newloc, loc, getcon(8, fn));
+	emit(Oload, i->cls, i->to, loc, R);
+	emit(Oload, Kl, loc, i->arg[0], R);
+}
+
+static void
+selvastart(Fn *fn, Params p, Ref ap)
+{
+	Ref rsave;
+	int s;
+
+	rsave = newtmp("abi", Kl, fn);
+	emit(Ostorel, Kw, R, rsave, ap);
+	s = p.stk > 2 + 8 * fn->vararg ? p.stk : 2 + p.ngp;
+	emit(Oaddr, Kl, rsave, SLOT(-s), R);
+}
+
+void
+rv64_abi(Fn *fn)
+{
+	Blk *b;
+	Ins *i, *i0, *ip;
+	Insl *il;
+	int n;
+	Params p;
+
+	for (b=fn->start; b; b=b->link)
+		b->visit = 0;
+
+	/* lower parameters */
+	for (b=fn->start, i=b->ins; i<&b->ins[b->nins]; i++)
+		if (!ispar(i->op))
+			break;
+	p = selpar(fn, b->ins, i);
+	n = b->nins - (i - b->ins) + (&insb[NIns] - curi);
+	i0 = alloc(n * sizeof(Ins));
+	ip = icpy(ip = i0, curi, &insb[NIns] - curi);
+	ip = icpy(ip, i, &b->ins[b->nins] - i);
+	b->nins = n;
+	b->ins = i0;
+
+	/* lower calls, returns, and vararg instructions */
+	il = 0;
+	b = fn->start;
+	do {
+		if (!(b = b->link))
+			b = fn->start; /* do it last */
+		if (b->visit)
+			continue;
+		curi = &insb[NIns];
+		selret(b, fn);
+		for (i=&b->ins[b->nins]; i!=b->ins;)
+			switch ((--i)->op) {
+			default:
+				emiti(*i);
+				break;
+			case Ocall:
+				for (i0=i; i0>b->ins; i0--)
+					if (!isarg((i0-1)->op))
+						break;
+				selcall(fn, i0, i, &il);
+				i = i0;
+				break;
+			case Ovastart:
+				selvastart(fn, p, i->arg[0]);
+				break;
+			case Ovaarg:
+				selvaarg(fn, i);
+				break;
+			case Oarg:
+			case Oargc:
+				die("unreachable");
+			}
+		if (b == fn->start)
+			for (; il; il=il->link)
+				emiti(il->i);
+		b->nins = &insb[NIns] - curi;
+		idup(&b->ins, curi, b->nins);
+	} while (b != fn->start);
+
+	if (debug['A']) {
+		fprintf(stderr, "\n> After ABI lowering:\n");
+		printfn(fn, stderr);
+	}
+}