great renaming campain!

1 files changed, 1135 insertions, 0 deletions

diff --git a/src/isel.c b/src/isel.c
new file mode 100644
index 0000000..48e29ef
--- /dev/null
+++ b/src/isel.c
@@ -0,0 +1,1135 @@
+#include "all.h"
+#include <limits.h>
+
+/* For x86_64, do the following:
+ *
+ * - lower calls
+ * - check that constants are used only in
+ *   places allowed
+ * - ensure immediates always fit in 32b
+ * - explicit machine register contraints
+ *   on instructions like division.
+ * - implement fast locals (the streak of
+ *   constant allocX in the first basic block)
+ * - recognize complex addressing modes
+ *
+ * Invariant: the use counts that are used
+ *            in sel() must be sound.  This
+ *            is not so trivial, maybe the
+ *            dce should be moved out...
+ */
+
+typedef struct ANum ANum;
+typedef struct AClass AClass;
+typedef struct RAlloc RAlloc;
+
+struct ANum {
+	char n, l, r;
+	Ins *i;
+	Ref mem;
+};
+
+static void amatch(Addr *, Ref, ANum *, Fn *, int);
+
+static int
+fcmptoi(int fc)
+{
+	switch (fc) {
+	default:   diag("isel: fcmptoi defaulted");
+	case FCle: return ICule;
+	case FClt: return ICult;
+	case FCgt: return ICugt;
+	case FCge: return ICuge;
+	case FCne: return ICne;
+	case FCeq: return ICeq;
+	case FCo:  return ICXnp;
+	case FCuo: return ICXp;
+	}
+}
+
+static int
+iscmp(int op, int *pk, int *pc)
+{
+	int k, c;
+
+	if (OCmpw <= op && op <= OCmpw1) {
+		c = op - OCmpw;
+		k = Kw;
+	}
+	else if (OCmpl <= op && op <= OCmpl1) {
+		c = op - OCmpl;
+		k = Kl;
+	}
+	else if (OCmps <= op && op <= OCmps1) {
+		c = fcmptoi(op - OCmps);
+		k = Ks;
+	}
+	else if (OCmpd <= op && op <= OCmpd1) {
+		c = fcmptoi(op - OCmpd);
+		k = Kd;
+	}
+	else
+		return 0;
+	if (pk)
+		*pk = k;
+	if (pc)
+		*pc = c;
+	return 1;
+}
+
+static int
+noimm(Ref r, Fn *fn)
+{
+	int64_t val;
+
+	if (rtype(r) != RCon)
+		return 0;
+	switch (fn->con[r.val].type) {
+	default:
+		diag("isel: invalid constant");
+	case CAddr:
+		/* we only support the 'small'
+		 * code model of the ABI, this
+		 * means that we can always
+		 * address data with 32bits
+		 */
+		return 0;
+	case CBits:
+		val = fn->con[r.val].bits.i;
+		return (val < INT32_MIN || val > INT32_MAX);
+	}
+}
+
+static int
+rslot(Ref r, Fn *fn)
+{
+	if (rtype(r) != RTmp)
+		return -1;
+	return fn->tmp[r.val].slot;
+}
+
+static int
+argcls(Ins *i, int n)
+{
+	return opdesc[i->op].argcls[n][i->cls];
+}
+
+static void
+fixarg(Ref *r, int k, int phi, Fn *fn)
+{
+	Addr a;
+	Ref r0, r1;
+	int s, n;
+
+	r1 = r0 = *r;
+	s = rslot(r0, fn);
+	if (KBASE(k) == 1 && rtype(r0) == RCon) {
+		/* load floating points from memory
+		 * slots, they can't be used as
+		 * immediates
+		 */
+		r1 = MEM(fn->nmem);
+		vgrow(&fn->mem, ++fn->nmem);
+		memset(&a, 0, sizeof a);
+		a.offset.type = CAddr;
+		n = stashfp(fn->con[r0.val].bits.i, KWIDE(k));
+		sprintf(a.offset.label, ".Lfp%d", n);
+		fn->mem[fn->nmem-1] = a;
+	}
+	else if (!phi && k == Kl && noimm(r0, fn)) {
+		/* load constants that do not fit in
+		 * a 32bit signed integer into a
+		 * long temporary
+		 */
+		r1 = newtmp("isel", Kl, fn);
+		emit(OCopy, Kl, r1, r0, R);
+	}
+	else if (s != -1) {
+		/* load fast locals' addresses into
+		 * temporaries right before the
+		 * instruction
+		 */
+		r1 = newtmp("isel", Kl, fn);
+		emit(OAddr, Kl, r1, SLOT(s), R);
+	}
+	*r = r1;
+}
+
+static void
+chuse(Ref r, int du, Fn *fn)
+{
+	if (rtype(r) == RTmp)
+		fn->tmp[r.val].nuse += du;
+}
+
+static void
+seladdr(Ref *r, ANum *an, Fn *fn)
+{
+	Addr a;
+	Ref r0, r1;
+
+	r0 = *r;
+	if (rtype(r0) == RTmp) {
+		chuse(r0, -1, fn);
+		r1 = an[r0.val].mem;
+		if (req(r1, R)) {
+			amatch(&a, r0, an, fn, 1);
+			vgrow(&fn->mem, ++fn->nmem);
+			fn->mem[fn->nmem-1] = a;
+			r1 = MEM(fn->nmem-1);
+			chuse(a.base, +1, fn);
+			chuse(a.index, +1, fn);
+			if (rtype(a.base) != RTmp)
+			if (rtype(a.index) != RTmp)
+				an[r0.val].mem = r1;
+		}
+		*r = r1;
+	}
+}
+
+static void
+selcmp(Ref arg[2], int k, Fn *fn)
+{
+	Ref r;
+
+	if (rtype(arg[0]) == RCon) {
+		r = arg[1];
+		arg[1] = arg[0];
+		arg[0] = r;
+	}
+	assert(rtype(arg[0]) != RCon);
+	emit(OXCmp, k, R, arg[1], arg[0]);
+	fixarg(&curi->arg[0], k, 0, fn);
+}
+
+static void
+sel(Ins i, ANum *an, Fn *fn)
+{
+	Ref r0, r1;
+	int x, k, kc;
+	int64_t val;
+	Ins *i0;
+
+	if (rtype(i.to) == RTmp)
+	if (!isreg(i.to) && !isreg(i.arg[0]) && !isreg(i.arg[1]))
+	if (fn->tmp[i.to.val].nuse == 0) {
+		chuse(i.arg[0], -1, fn);
+		chuse(i.arg[1], -1, fn);
+		return;
+	}
+	i0 = curi;
+	k = i.cls;
+	switch (i.op) {
+	case ODiv:
+	case ORem:
+	case OUDiv:
+	case OURem:
+		if (i.op == ODiv || i.op == OUDiv)
+			r0 = TMP(RAX), r1 = TMP(RDX);
+		else
+			r0 = TMP(RDX), r1 = TMP(RAX);
+		emit(OCopy, k, i.to, r0, R);
+		emit(OCopy, k, R, r1, R);
+		if (rtype(i.arg[1]) == RCon) {
+			/* immediates not allowed for
+			 * divisions in x86
+			 */
+			r0 = newtmp("isel", k, fn);
+		} else
+			r0 = i.arg[1];
+		if (i.op == ODiv || i.op == ORem) {
+			emit(OXIDiv, k, R, r0, R);
+			emit(OSign, k, TMP(RDX), TMP(RAX), R);
+		} else {
+			emit(OXDiv, k, R, r0, R);
+			emit(OCopy, k, TMP(RDX), CON_Z, R);
+		}
+		emit(OCopy, k, TMP(RAX), i.arg[0], R);
+		if (rtype(i.arg[1]) == RCon)
+			emit(OCopy, k, r0, i.arg[1], R);
+		break;
+	case OSar:
+	case OShr:
+	case OShl:
+		if (rtype(i.arg[1]) == RCon)
+			goto Emit;
+		r0 = i.arg[1];
+		i.arg[1] = TMP(RCX);
+		emit(OCopy, Kw, R, TMP(RCX), R);
+		emiti(i);
+		emit(OCopy, Kw, TMP(RCX), r0, R);
+		break;
+	case ONop:
+		break;
+	case OStored:
+	case OStores:
+	case OStorel:
+	case OStorew:
+	case OStoreh:
+	case OStoreb:
+		if (rtype(i.arg[0]) == RCon) {
+			if (i.op == OStored)
+				i.op = OStorel;
+			if (i.op == OStores)
+				i.op = OStorew;
+		}
+		seladdr(&i.arg[1], an, fn);
+		goto Emit;
+	case_OLoad:
+		seladdr(&i.arg[0], an, fn);
+		goto Emit;
+	case OCall:
+	case OSAlloc:
+	case OCopy:
+	case OAdd:
+	case OSub:
+	case OMul:
+	case OAnd:
+	case OOr:
+	case OXor:
+	case OXTest:
+	case OFtosi:
+	case OSitof:
+	case OExts:
+	case OTruncd:
+	case OCast:
+	case_OExt:
+Emit:
+		emiti(i);
+		fixarg(&curi->arg[0], argcls(curi, 0), 0, fn);
+		fixarg(&curi->arg[1], argcls(curi, 1), 0, fn);
+		break;
+	case OAlloc:
+	case OAlloc+1:
+	case OAlloc+2: /* == OAlloc1 */
+		/* we need to make sure
+		 * the stack remains aligned
+		 * (rsp = 0) mod 16
+		 */
+		if (rtype(i.arg[0]) == RCon) {
+			assert(fn->con[i.arg[0].val].type == CBits);
+			val = fn->con[i.arg[0].val].bits.i;
+			val = (val + 15)  & ~INT64_C(15);
+			if (val < 0 || val > INT32_MAX)
+				diag("isel: alloc too large");
+			emit(OSAlloc, Kl, i.to, getcon(val, fn), R);
+		} else {
+			/* r0 = (i.arg[0] + 15) & -16 */
+			r0 = newtmp("isel", Kl, fn);
+			r1 = newtmp("isel", Kl, fn);
+			emit(OSAlloc, Kl, i.to, r0, R);
+			emit(OAnd, Kl, r0, r1, getcon(-16, fn));
+			emit(OAdd, Kl, r1, i.arg[0], getcon(15, fn));
+		}
+		break;
+	default:
+		if (isext(i.op))
+			goto case_OExt;
+		if (isload(i.op))
+			goto case_OLoad;
+		if (iscmp(i.op, &kc, &x)) {
+			if (rtype(i.arg[0]) == RCon)
+				x = icmpop(x);
+			emit(OXSet+x, k, i.to, R, R);
+			selcmp(i.arg, kc, fn);
+			break;
+		}
+		diag("isel: non-exhaustive implementation");
+	}
+
+	while (i0 > curi && --i0)
+		if (rslot(i0->arg[0], fn) != -1
+		||  rslot(i0->arg[1], fn) != -1)
+			diag("isel: usupported address argument");
+}
+
+static Ins *
+flagi(Ins *i0, Ins *i)
+{
+	while (i>i0) {
+		i--;
+		if (opdesc[i->op].sflag)
+			return i;
+		if (opdesc[i->op].lflag)
+			continue;
+		return 0;
+	}
+	return 0;
+}
+
+struct AClass {
+	int inmem;
+	int align;
+	uint size;
+	int cls[2];
+};
+
+static void
+aclass(AClass *a, Typ *t)
+{
+	int e, s, n, cls;
+	uint sz, al;
+
+	sz = t->size;
+	al = 1u << t->align;
+
+	/* the ABI requires sizes to be rounded
+	 * up to the nearest multiple of 8, moreover
+	 * it makes it easy load and store structures
+	 * in registers
+	 */
+	if (al < 8)
+		al = 8;
+	sz = (sz + al-1) & -al;
+
+	a->size = sz;
+	a->align = t->align;
+
+	if (t->dark || sz > 16) {
+		/* large or unaligned structures are
+		 * required to be passed in memory
+		 */
+		a->inmem = 1;
+		return;
+	}
+
+	a->inmem = 0;
+	for (e=0, s=0; e<2; e++) {
+		cls = -1;
+		for (n=0; n<8 && t->seg[s].len; s++) {
+			if (t->seg[s].ispad) {
+				/* don't change anything */
+			}
+			else if (t->seg[s].isflt) {
+				if (cls == -1)
+					cls = Kd;
+			}
+			else
+				cls = Kl;
+			n += t->seg[s].len;
+		}
+		assert(n <= 8);
+		a->cls[e] = cls;
+	}
+}
+
+static void
+blit(Ref rstk, uint soff, Ref rsrc, uint sz, Fn *fn)
+{
+	Ref r, r1;
+	uint boff;
+
+	/* it's an impolite blit, we might go across the end
+	 * of the source object a little bit... */
+	for (boff=0; sz>0; sz-=8, soff+=8, boff+=8) {
+		r = newtmp("abi", Kl, fn);
+		r1 = newtmp("abi", Kl, fn);
+		emit(OStorel, 0, R, r, r1);
+		emit(OAdd, Kl, r1, rstk, getcon(soff, fn));
+		r1 = newtmp("abi", Kl, fn);
+		emit(OLoad, Kl, r, r1, R);
+		emit(OAdd, Kl, r1, rsrc, getcon(boff, fn));
+		chuse(rsrc, +1, fn);
+		chuse(rstk, +1, fn);
+	}
+}
+
+static int
+retr(Ref reg[2], AClass *aret)
+{
+	static int retreg[2][2] = {{RAX, RDX}, {XMM0, XMM0+1}};
+	int n, k, ca, nr[2];
+
+	nr[0] = nr[1] = 0;
+	ca = 0;
+	for (n=0; aret->cls[n]>=0 && n<2; n++) {
+		k = KBASE(aret->cls[n]);
+		reg[n] = TMP(retreg[k][nr[k]++]);
+		ca += 1 << (2 * k);
+	}
+	return ca;
+}
+
+static void
+selret(Blk *b, Fn *fn)
+{
+	int j, k, ca;
+	Ref r, r0, reg[2];
+	AClass aret;
+
+	j = b->jmp.type;
+
+	if (!isret(j) || j == JRet0)
+		return;
+
+	r0 = b->jmp.arg;
+	b->jmp.type = JRet0;
+
+	if (j == JRetc) {
+		aclass(&aret, &typ[fn->retty]);
+		if (aret.inmem) {
+			assert(rtype(fn->retr) == RTmp);
+			emit(OCopy, Kl, TMP(RAX), fn->retr, R);
+			chuse(fn->retr, +1, fn);
+			blit(fn->retr, 0, r0, aret.size, fn);
+			ca = 1;
+		} else {
+			ca = retr(reg, &aret);
+			if (aret.size > 8) {
+				r = newtmp("abi", Kl, fn);
+				emit(OLoad, Kl, reg[1], r, R);
+				emit(OAdd, Kl, r, r0, getcon(8, fn));
+				chuse(r0, +1, fn);
+			}
+			emit(OLoad, Kl, reg[0], r0, R);
+		}
+	} else {
+		k = j - JRetw;
+		if (KBASE(k) == 0) {
+			emit(OCopy, k, TMP(RAX), r0, R);
+			ca = 1;
+		} else {
+			emit(OCopy, k, TMP(XMM0), r0, R);
+			ca = 1 << 2;
+		}
+	}
+
+	b->jmp.arg = CALL(ca);
+}
+
+static void
+seljmp(Blk *b, Fn *fn)
+{
+	Ref r;
+	int c, k;
+	Ins *fi;
+
+	if (b->jmp.type == JRet0 || b->jmp.type == JJmp)
+		return;
+	assert(b->jmp.type == JJnz);
+	r = b->jmp.arg;
+	b->jmp.arg = R;
+	assert(!req(r, R));
+	if (rtype(r) == RCon) {
+		b->jmp.type = JJmp;
+		if (req(r, CON_Z))
+			b->s1 = b->s2;
+		b->s2 = 0;
+		return;
+	}
+	fi = flagi(b->ins, &b->ins[b->nins]);
+	if (fi && req(fi->to, r)) {
+		if (iscmp(fi->op, &k, &c)) {
+			if (rtype(fi->arg[0]) == RCon)
+				c = icmpop(c);
+			b->jmp.type = JXJc + c;
+			if (fn->tmp[r.val].nuse == 1) {
+				assert(fn->tmp[r.val].ndef == 1);
+				selcmp(fi->arg, k, fn);
+				*fi = (Ins){.op = ONop};
+			}
+			return;
+		}
+		if (fi->op == OAnd && fn->tmp[r.val].nuse == 1
+		&& (rtype(fi->arg[0]) == RTmp ||
+		    rtype(fi->arg[1]) == RTmp)) {
+			fi->op = OXTest;
+			fi->to = R;
+			b->jmp.type = JXJc + ICne;
+			if (rtype(fi->arg[1]) == RCon) {
+				r = fi->arg[1];
+				fi->arg[1] = fi->arg[0];
+				fi->arg[0] = r;
+			}
+			return;
+		}
+		/* since flags are not tracked in liveness,
+		 * the result of the flag-setting instruction
+		 * has to be marked as live
+		 */
+		if (fn->tmp[r.val].nuse == 1)
+			emit(OCopy, Kw, R, r, R);
+		b->jmp.type = JXJc + ICne;
+		return;
+	}
+	selcmp((Ref[2]){r, CON_Z}, Kw, fn); /* todo, add long branch if non-zero */
+	b->jmp.type = JXJc + ICne;
+}
+
+static int
+classify(Ins *i0, Ins *i1, AClass *ac, int op, AClass *aret)
+{
+	int nint, ni, nsse, ns, n, *pn;
+	AClass *a;
+	Ins *i;
+
+	if (aret && aret->inmem)
+		nint = 5; /* hidden argument */
+	else
+		nint = 6;
+	nsse = 8;
+	for (i=i0, a=ac; i<i1; i++, a++) {
+		if (i->op == op) {
+			if (KBASE(i->cls) == 0)
+				pn = &nint;
+			else
+				pn = &nsse;
+			if (*pn > 0) {
+				--*pn;
+				a->inmem = 0;
+			} else
+				a->inmem = 2;
+			a->align = 3;
+			a->size = 8;
+			a->cls[0] = i->cls;
+		} else {
+			n = i->arg[0].val & AMask;
+			aclass(a, &typ[n]);
+			if (a->inmem)
+				continue;
+			ni = ns = 0;
+			for (n=0; n<2; n++)
+				if (KBASE(a->cls[n]) == 0)
+					ni++;
+				else
+					ns++;
+			if (nint >= ni && nsse >= ns) {
+				nint -= ni;
+				nsse -= ns;
+			} else
+				a->inmem = 1;
+		}
+	}
+
+	return ((6-nint) << 4) | ((8-nsse) << 8);
+}
+
+int rsave[] = {
+	RDI, RSI, RDX, RCX, R8, R9, R10, R11, RAX,
+	XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7,
+	XMM8, XMM9, XMM10, XMM11, XMM12, XMM13, XMM14
+};
+int rclob[] = {RBX, R12, R13, R14, R15};
+
+MAKESURE(rsave_has_correct_size, sizeof rsave == NRSave * sizeof(int));
+MAKESURE(rclob_has_correct_size, sizeof rclob == NRClob * sizeof(int));
+
+bits
+retregs(Ref r, int p[2])
+{
+	bits b;
+	int ni, nf;
+
+	assert(rtype(r) == RACall);
+	b = 0;
+	ni = r.val & 3;
+	nf = (r.val >> 2) & 3;
+	if (ni >= 1)
+		b |= BIT(RAX);
+	if (ni >= 2)
+		b |= BIT(RDX);
+	if (nf >= 1)
+		b |= BIT(XMM0);
+	if (nf >= 2)
+		b |= BIT(XMM1);
+	if (p) {
+		p[0] = ni;
+		p[1] = nf;
+	}
+	return b;
+}
+
+bits
+argregs(Ref r, int p[2])
+{
+	bits b;
+	int j, ni, nf;
+
+	assert(rtype(r) == RACall);
+	b = 0;
+	ni = (r.val >> 4) & 15;
+	nf = (r.val >> 8) & 15;
+	for (j=0; j<ni; j++)
+		b |= BIT(rsave[j]);
+	for (j=0; j<nf; j++)
+		b |= BIT(XMM0+j);
+	if (p) {
+		p[0] = ni + 1;
+		p[1] = nf;
+	}
+	return b | BIT(RAX);
+}
+
+static Ref
+rarg(int ty, int *ni, int *ns)
+{
+	if (KBASE(ty) == 0)
+		return TMP(rsave[(*ni)++]);
+	else
+		return TMP(XMM0 + (*ns)++);
+}
+
+struct RAlloc {
+	Ins i;
+	RAlloc *link;
+};
+
+static void
+selcall(Fn *fn, Ins *i0, Ins *i1, RAlloc **rap)
+{
+	Ins *i;
+	AClass *ac, *a, aret;
+	int ca, ni, ns;
+	uint stk, off;
+	Ref r, r1, r2, reg[2], regcp[2];
+	RAlloc *ra;
+
+	ac = alloc((i1-i0) * sizeof ac[0]);
+	if (!req(i1->arg[1], R)) {
+		assert(rtype(i1->arg[1]) == RAType);
+		aclass(&aret, &typ[i1->arg[1].val & AMask]);
+		ca = classify(i0, i1, ac, OArg, &aret);
+	} else
+		ca = classify(i0, i1, ac, OArg, 0);
+
+	for (stk=0, a=&ac[i1-i0]; a>ac;)
+		if ((--a)->inmem) {
+			assert(a->align <= 4);
+			stk += a->size;
+			if (a->align == 4)
+				stk += stk & 15;
+		}
+	stk += stk & 15;
+	if (stk) {
+		r = getcon(-(int64_t)stk, fn);
+		emit(OSAlloc, Kl, R, r, R);
+	}
+
+	if (!req(i1->arg[1], R)) {
+		if (aret.inmem) {
+			/* get the return location from eax
+			 * it saves one callee-save reg */
+			r1 = newtmp("abi", Kl, fn);
+			emit(OCopy, Kl, i1->to, TMP(RAX), R);
+			ca += 1;
+		} else {
+			if (aret.size > 8) {
+				r = newtmp("abi", Kl, fn);
+				regcp[1] = newtmp("abi", aret.cls[1], fn);
+				emit(OStorel, 0, R, regcp[1], r);
+				emit(OAdd, Kl, r, i1->to, getcon(8, fn));
+				chuse(i1->to, +1, fn);
+				ca += 1 << (2 * KBASE(aret.cls[1]));
+			}
+			regcp[0] = newtmp("abi", aret.cls[0], fn);
+			emit(OStorel, 0, R, regcp[0], i1->to);
+			ca += 1 << (2 * KBASE(aret.cls[0]));
+			retr(reg, &aret);
+			if (aret.size > 8)
+				emit(OCopy, aret.cls[1], regcp[1], reg[1], R);
+			emit(OCopy, aret.cls[0], regcp[0], reg[0], R);
+			r1 = i1->to;
+		}
+		/* allocate return pad */
+		ra = alloc(sizeof *ra);
+		assert(NAlign == 3);
+		aret.align -= 2;
+		if (aret.align < 0)
+			aret.align = 0;
+		ra->i.op = OAlloc + aret.align;
+		ra->i.cls = Kl;
+		ra->i.to = r1;
+		ra->i.arg[0] = getcon(aret.size, fn);
+		ra->link = (*rap);
+		*rap = ra;
+	} else {
+		ra = 0;
+		if (KBASE(i1->cls) == 0) {
+			emit(OCopy, i1->cls, i1->to, TMP(RAX), R);
+			ca += 1;
+		} else {
+			emit(OCopy, i1->cls, i1->to, TMP(XMM0), R);
+			ca += 1 << 2;
+		}
+	}
+	emit(OCall, i1->cls, R, i1->arg[0], CALL(ca));
+	emit(OCopy, Kw, TMP(RAX), getcon((ca >> 8) & 15, fn), R);
+
+	ni = ns = 0;
+	if (ra && aret.inmem)
+		emit(OCopy, Kl, rarg(Kl, &ni, &ns), ra->i.to, R); /* pass hidden argument */
+	for (i=i0, a=ac; i<i1; i++, a++) {
+		if (a->inmem)
+			continue;
+		r1 = rarg(a->cls[0], &ni, &ns);
+		if (i->op == OArgc) {
+			if (a->size > 8) {
+				r2 = rarg(a->cls[1], &ni, &ns);
+				r = newtmp("abi", Kl, fn);
+				emit(OLoad, a->cls[1], r2, r, R);
+				emit(OAdd, Kl, r, i->arg[1], getcon(8, fn));
+				chuse(i->arg[1], +1, fn);
+			}
+			emit(OLoad, a->cls[0], r1, i->arg[1], R);
+		} else
+			emit(OCopy, i->cls, r1, i->arg[0], R);
+	}
+
+	if (!stk)
+		return;
+
+	r = newtmp("abi", Kl, fn);
+	chuse(r, -1, fn);
+	for (i=i0, a=ac, off=0; i<i1; i++, a++) {
+		if (!a->inmem)
+			continue;
+		if (i->op == OArgc) {
+			if (a->align == 4)
+				off += off & 15;
+			blit(r, off, i->arg[1], a->size, fn);
+		} else {
+			r1 = newtmp("abi", Kl, fn);
+			emit(OStorel, 0, R, i->arg[0], r1);
+			emit(OAdd, Kl, r1, r, getcon(off, fn));
+			chuse(r, +1, fn);
+		}
+		off += a->size;
+	}
+	emit(OSAlloc, Kl, r, getcon(stk, fn), R);
+}
+
+static void
+selpar(Fn *fn, Ins *i0, Ins *i1)
+{
+	AClass *ac, *a, aret;
+	Ins *i;
+	int ni, ns, s, al;
+	Ref r, r1;
+
+	ac = alloc((i1-i0) * sizeof ac[0]);
+	curi = insb;
+	ni = ns = 0;
+
+	if (fn->retty >= 0) {
+		aclass(&aret, &typ[fn->retty]);
+		if (aret.inmem) {
+			r = newtmp("abi", Kl, fn);
+			*curi++ = (Ins){OCopy, r, {rarg(Kl, &ni, &ns)}, Kl};
+			fn->retr = r;
+		}
+		classify(i0, i1, ac, OPar, &aret);
+	} else
+		classify(i0, i1, ac, OPar, 0);
+
+	assert(NAlign == 3);
+
+	s = 4;
+	for (i=i0, a=ac; i<i1; i++, a++) {
+		switch (a->inmem) {
+		case 1:
+			assert(a->align <= 4);
+			if (a->align == 4)
+				s = (s+3) & -4;
+			fn->tmp[i->to.val].slot = -s; /* HACK! */
+			s += a->size / 4;
+			continue;
+		case 2:
+			*curi++ = (Ins){OLoad, i->to, {SLOT(-s)}, i->cls};
+			s += 2;
+			continue;
+		}
+		r1 = rarg(a->cls[0], &ni, &ns);
+		if (i->op == OParc) {
+			r = newtmp("abi", Kl, fn);
+			*curi++ = (Ins){OCopy, r, {r1}, Kl};
+			a->cls[0] = r.val;
+			if (a->size > 8) {
+				r1 = rarg(a->cls[1], &ni, &ns);
+				r = newtmp("abi", Kl, fn);
+				*curi++ = (Ins){OCopy, r, {r1}, Kl};
+				a->cls[1] = r.val;
+			}
+		} else
+			*curi++ = (Ins){OCopy, i->to, {r1}, i->cls};
+	}
+	for (i=i0, a=ac; i<i1; i++, a++) {
+		if (i->op != OParc || a->inmem)
+			continue;
+		assert(NAlign == 3);
+		for (al=0; a->align >> (al+2); al++)
+			;
+		r = TMP(a->cls[0]);
+		r1 = i->to;
+		*curi++ = (Ins){OAlloc+al, r1, {getcon(a->size, fn)}, Kl};
+		*curi++ = (Ins){OStorel, R, {r, r1}, 0};
+		if (a->size > 8) {
+			r = newtmp("abi", Kl, fn);
+			*curi++ = (Ins){OAdd, r, {r1, getcon(8, fn)}, Kl};
+			r1 = TMP(a->cls[1]);
+			*curi++ = (Ins){OStorel, R, {r1, r}, 0};
+		}
+	}
+}
+
+static int
+aref(Ref r, ANum *ai)
+{
+	switch (rtype(r)) {
+	default:
+		diag("isel: aref defaulted");
+	case RCon:
+		return 2;
+	case RTmp:
+		return ai[r.val].n;
+	}
+}
+
+static int
+ascale(Ref r, Con *con)
+{
+	int64_t n;
+
+	if (rtype(r) != RCon)
+		return 0;
+	if (con[r.val].type != CBits)
+		return 0;
+	n = con[r.val].bits.i;
+	return n == 1 || n == 2 || n == 4 || n == 8;
+}
+
+static void
+anumber(ANum *ai, Blk *b, Con *con)
+{
+	/* This should be made obsolete by a proper
+	 * reassoc pass.
+	 *
+	 * Rules:
+	 *
+	 *   RTmp(_) -> 0    tmp
+	 *   ( RTmp(_) -> 1    slot )
+	 *   RCon(_) -> 2    con
+	 *   0 * 2   -> 3    s * i (when constant is 1,2,4,8)
+	 */
+	static char add[10][10] = {
+		[2] [2] = 2,              /* folding */
+		[2] [5] = 5, [5] [2] = 5,
+		[2] [6] = 6, [6] [2] = 6,
+		[2] [7] = 7, [7] [2] = 7,
+		[0] [0] = 4,              /* 4: b + s * i */
+		[0] [3] = 4, [3] [0] = 4,
+		[2] [3] = 5, [3] [2] = 5, /* 5: o + s * i */
+		[0] [2] = 6, [2] [0] = 6, /* 6: o + b */
+		[2] [4] = 7, [4] [2] = 7, /* 7: o + b + s * i */
+		[0] [5] = 7, [5] [0] = 7,
+		[6] [3] = 7, [3] [6] = 7,
+
+	};
+	int a, a1, a2, n1, n2, t1, t2;
+	Ins *i;
+
+	for (i=b->ins; i-b->ins < b->nins; i++) {
+		if (rtype(i->to) == RTmp)
+			ai[i->to.val].i = i;
+		if (i->op != OAdd && i->op != OMul)
+			continue;
+		a1 = aref(i->arg[0], ai);
+		a2 = aref(i->arg[1], ai);
+		t1 = a1 != 1 && a1 != 2;
+		t2 = a2 != 1 && a2 != 2;
+		if (i->op == OAdd) {
+			a = add[n1 = a1][n2 = a2];
+			if (t1 && a < add[0][a2])
+				a = add[n1 = 0][n2 = a2];
+			if (t2 && a < add[a1][0])
+				a = add[n1 = a1][n2 = 0];
+			if (t1 && t2 && a < add[0][0])
+				a = add[n1 = 0][n2 = 0];
+		} else {
+			n1 = n2 = a = 0;
+			if (ascale(i->arg[0], con) && t2)
+				a = 3, n1 = 2, n2 = 0;
+			if (t1 && ascale(i->arg[1], con))
+				a = 3, n1 = 0, n2 = 2;
+		}
+		ai[i->to.val].n = a;
+		ai[i->to.val].l = n1;
+		ai[i->to.val].r = n2;
+	}
+}
+
+static void
+amatch(Addr *a, Ref r, ANum *ai, Fn *fn, int top)
+{
+	Ins *i;
+	int nl, nr, t, s;
+	Ref al, ar;
+
+	if (top)
+		memset(a, 0, sizeof *a);
+	if (rtype(r) == RCon) {
+		addcon(&a->offset, &fn->con[r.val]);
+		return;
+	}
+	assert(rtype(r) == RTmp);
+	i = ai[r.val].i;
+	nl = ai[r.val].l;
+	nr = ai[r.val].r;
+	if (i) {
+		if (nl > nr) {
+			al = i->arg[1];
+			ar = i->arg[0];
+			t = nl, nl = nr, nr = t;
+		} else {
+			al = i->arg[0];
+			ar = i->arg[1];
+		}
+	}
+	switch (ai[r.val].n) {
+	default:
+		diag("isel: amatch defaulted");
+	case 3: /* s * i */
+		if (!top) {
+			a->index = al;
+			a->scale = fn->con[ar.val].bits.i;
+		} else
+			a->base = r;
+		break;
+	case 4: /* b + s * i */
+		switch (nr) {
+		case 0:
+			if (fn->tmp[ar.val].slot != -1) {
+				al = i->arg[1];
+				ar = i->arg[0];
+			}
+			a->index = ar;
+			a->scale = 1;
+			break;
+		case 3:
+			amatch(a, ar, ai, fn, 0);
+			break;
+		}
+		r = al;
+	case 0:
+		s = fn->tmp[r.val].slot;
+		if (s != -1)
+			r = SLOT(s);
+		a->base = r;
+		break;
+	case 2: /* constants */
+	case 5: /* o + s * i */
+	case 6: /* o + b */
+	case 7: /* o + b + s * i */
+		amatch(a, ar, ai, fn, 0);
+		amatch(a, al, ai, fn, 0);
+		break;
+	}
+}
+
+/* instruction selection
+ * requires use counts (as given by parsing)
+ */
+void
+isel(Fn *fn)
+{
+	Blk *b, **sb;
+	Ins *i, *i0, *ip;
+	Phi *p;
+	uint a;
+	int n, al;
+	int64_t sz;
+	ANum *ainfo;
+	RAlloc *ral;
+
+	for (n=0; n<fn->ntmp; n++)
+		fn->tmp[n].slot = -1;
+	fn->slot = 0;
+
+	/* lower arguments */
+	for (b=fn->start, i=b->ins; i-b->ins < b->nins; i++)
+		if (i->op != OPar && i->op != OParc)
+			break;
+	selpar(fn, b->ins, i);
+	n = b->nins - (i - b->ins) + (curi - insb);
+	i0 = alloc(n * sizeof(Ins));
+	ip = icpy(ip = i0, insb, curi - insb);
+	ip = icpy(ip, i, &b->ins[b->nins] - i);
+	b->nins = n;
+	b->ins = i0;
+
+	/* lower function calls and returns */
+	ral = 0;
+	b = fn->start;
+	do {
+		if (!(b = b->link))
+			b = fn->start; /* do it last */
+		curi = &insb[NIns];
+		selret(b, fn);
+		for (i=&b->ins[b->nins]; i!=b->ins;) {
+			if ((--i)->op == OCall) {
+				for (i0=i; i0>b->ins; i0--)
+					if ((i0-1)->op != OArg)
+					if ((i0-1)->op != OArgc)
+						break;
+				selcall(fn, i0, i, &ral);
+				i = i0;
+				continue;
+			}
+			assert(i->op != OArg && i->op != OArgc);
+			emiti(*i);
+		}
+		if (b == fn->start)
+			for (; ral; ral=ral->link)
+				emiti(ral->i);
+		b->nins = &insb[NIns] - curi;
+		idup(&b->ins, curi, b->nins);
+	} while (b != fn->start);
+
+	if (debug['A']) {
+		fprintf(stderr, "\n> After call lowering:\n");
+		printfn(fn, stderr);
+	}
+
+	/* assign slots to fast allocs */
+	b = fn->start;
+	assert(NAlign == 3 && "change n=4 and sz /= 4 below");
+	for (al=OAlloc, n=4; al<=OAlloc1; al++, n*=2)
+		for (i=b->ins; i-b->ins < b->nins; i++)
+			if (i->op == al) {
+				if (rtype(i->arg[0]) != RCon)
+					break;
+				sz = fn->con[i->arg[0].val].bits.i;
+				if (sz < 0 || sz >= INT_MAX-3)
+					diag("isel: invalid alloc size");
+				sz = (sz + n-1) & -n;
+				sz /= 4;
+				fn->tmp[i->to.val].slot = fn->slot;
+				fn->slot += sz;
+				*i = (Ins){.op = ONop};
+			}
+
+	/* process basic blocks */
+	n = fn->ntmp;
+	ainfo = emalloc(n * sizeof ainfo[0]);
+	for (b=fn->start; b; b=b->link) {
+		curi = &insb[NIns];
+		for (sb=(Blk*[3]){b->s1, b->s2, 0}; *sb; sb++)
+			for (p=(*sb)->phi; p; p=p->link) {
+				for (a=0; p->blk[a] != b; a++)
+					assert(a+1 < p->narg);
+				fixarg(&p->arg[a], p->cls, 1, fn);
+			}
+		memset(ainfo, 0, n * sizeof ainfo[0]);
+		anumber(ainfo, b, fn->con);
+		seljmp(b, fn);
+		for (i=&b->ins[b->nins]; i!=b->ins;)
+			sel(*--i, ainfo, fn);
+		b->nins = &insb[NIns] - curi;
+		idup(&b->ins, curi, b->nins);
+	}
+	free(ainfo);
+
+	if (debug['I']) {
+		fprintf(stderr, "\n> After instruction selection:\n");
+		printfn(fn, stderr);
+	}
+}