use a new Ref type for registers

This might not be a good idea, the problem was that
many spurious registers would be added to the Bits
data-structures during compilation (and would
always remain 0).  However, doing the above
modification de-uniformizes the handling of temps
and regs, this makes the code longer and not
really nicer.  Also, additional Bits structures
are required to track the registers independently.

Overall this might be a bad idea to revert.

1 files changed, 84 insertions, 67 deletions

diff --git a/lisc/spill.c b/lisc/spill.c
index 921a81c..64200af 100644
--- a/lisc/spill.c
+++ b/lisc/spill.c
@@ -13,7 +13,7 @@ loopmark(Blk *hd, Blk *b, Phi *p)
 	for (; p; p=p->link)
 		for (a=0; a<p->narg; a++)
 			if (p->blk[a] == b)
-			if (rtype(p->arg[a]) == RSym)
+			if (rtype(p->arg[a]) == RTmp)
 				BSET(hd->gen, p->arg[a].val);
 	if (b->visit == head)
 		return;
@@ -30,20 +30,16 @@ loopmark(Blk *hd, Blk *b, Phi *p)
 }
 
 static void
-symuse(Ref r, int use, int loop, Fn *fn)
+tmpuse(Ref r, int use, int loop, Fn *fn)
 {
-	Sym *s;
+	Tmp *t;
 
-	if (rtype(r) != RSym)
+	if (rtype(r) != RTmp)
 		return;
-	s = &fn->sym[r.val];
-	if (s->type != STmp)
-		return;
-	if (use)
-		s->nuse++;
-	else
-		s->ndef++;
-	s->cost += loop;
+	t = &fn->tmp[r.val];
+	t->nuse += use;
+	t->ndef += 1 - use;
+	t->cost += loop;
 }
 
 /* evaluate spill costs of temporaries,
@@ -57,7 +53,7 @@ fillcost(Fn *fn)
 	uint a;
 	Blk *b;
 	Ins *i;
-	Sym *s;
+	Tmp *t;
 	Phi *p;
 
 	for (b=fn->start; b; b=b->link) {
@@ -77,43 +73,41 @@ fillcost(Fn *fn)
 		if (hd && debug['S']) {
 			fprintf(stderr, "\t%-10s", b->name);
 			fprintf(stderr, " (% 3d) ", b->nlive);
-			dumpss(&b->gen, fn->sym, stderr);
+			dumpts(&b->gen, fn->tmp, stderr);
 		}
 	}
-	for (s=fn->sym; s-fn->sym < fn->ntmp; s++) {
-		s->cost = 0;
-		s->nuse = 0;
-		s->ndef = 0;
-		if (s->type == SReg)
-			s->cost = 100000;
+	for (t=fn->tmp; t-fn->tmp < fn->ntmp; t++) {
+		t->cost = 0;
+		t->nuse = 0;
+		t->ndef = 0;
 	}
 	for (b=fn->start; b; b=b->link) {
 		for (p=b->phi; p; p=p->link) {
-			/* zero cost for temporaries used
-			 * in phi instructions */
-			symuse(p->to, 0, 0, fn);
+			/* todo, the cost computation
+			 * for p->to is not great... */
+			tmpuse(p->to, 0, 0, fn);
 			for (a=0; a<p->narg; a++) {
 				n = p->blk[a]->loop;
 				assert(b->npred==p->narg &&
 					"wrong cfg");
 				n /= b->npred;
-				symuse(p->arg[a], 1, n, fn);
+				tmpuse(p->arg[a], 1, n, fn);
 			}
 		}
 		n = b->loop;
 		for (i=b->ins; i-b->ins < b->nins; i++) {
-			symuse(i->to, 0, n, fn);
-			symuse(i->arg[0], 1, n, fn);
-			symuse(i->arg[1], 1, n, fn);
+			tmpuse(i->to, 0, n, fn);
+			tmpuse(i->arg[0], 1, n, fn);
+			tmpuse(i->arg[1], 1, n, fn);
 		}
-		symuse(b->jmp.arg, 1, n, fn);
+		tmpuse(b->jmp.arg, 1, n, fn);
 	}
 	if (debug['S']) {
 		fprintf(stderr, "\n> Spill costs:\n");
-		for (n=Tmp0; n<fn->ntmp; n++)
+		for (n=0; n<fn->ntmp; n++)
 			fprintf(stderr, "\t%-10s %d\n",
-				fn->sym[n].name,
-				fn->sym[n].cost);
+				fn->tmp[n].name,
+				fn->tmp[n].cost);
 		fprintf(stderr, "\n");
 	}
 }
@@ -148,14 +142,16 @@ bcnt(Bits *b) /* glad I can pull it :) */
 
 extern Ins insb[NIns], *curi; /* shared work buffer */
 static Bits *f;  /* temps to prioritize in registers (for tcmp1) */
-static Sym *sym; /* current symbol table (for tcmpX) */
+static Tmp *tmp; /* current temporaries (for tcmpX) */
 static int ntmp; /* current # of temps (for limit) */
 static uint ns;  /* current # of spill slots */
+static int nreg; /* # of registers available */
+static Bits br;  /* live registers */
 
 static int
 tcmp0(const void *pa, const void *pb)
 {
-	return sym[*(int *)pb].cost - sym[*(int *)pa].cost;
+	return tmp[*(int *)pb].cost - tmp[*(int *)pa].cost;
 }
 
 static int
@@ -172,11 +168,10 @@ slot(int t)
 {
 	int s;
 
-	assert(sym[t].type == STmp);
-	s = sym[t].spill;
+	s = tmp[t].spill;
 	if (!s) {
-		s = 1 + ns++;
-		sym[t].spill = s;
+		s = ++ns;
+		tmp[t].spill = s;
 	}
 	return SLOT(s);
 }
@@ -192,7 +187,7 @@ emit(short op, Ref to, Ref arg0, Ref arg1)
 static Bits
 limit(Bits *b, int k, Bits *fst)
 {
-	static int *tmp, maxt;
+	static int *tarr, maxt;
 	int i, t, nt;
 	Bits res;
 
@@ -200,28 +195,28 @@ limit(Bits *b, int k, Bits *fst)
 	if (nt <= k)
 		return *b;
 	if (nt > maxt) {
-		free(tmp);
-		tmp = alloc(nt * sizeof tmp[0]);
+		free(tarr);
+		tarr = alloc(nt * sizeof tarr[0]);
 		maxt = nt;
 	}
 	i = 0;
 	for (t=0; t<ntmp; t++)
 		if (BGET(*b, t))
-			tmp[i++] = t;
+			tarr[i++] = t;
 	assert(i == nt);
 	if (!fst)
-		qsort(tmp, nt, sizeof tmp[0], tcmp0);
+		qsort(tarr, nt, sizeof tarr[0], tcmp0);
 	else {
 		f = fst;
-		qsort(tmp, nt, sizeof tmp[0], tcmp1);
+		qsort(tarr, nt, sizeof tarr[0], tcmp1);
 	}
 	res = (Bits){{0}};
 	for (i=0; i<k && i<nt; i++)
-		BSET(res, tmp[i]);
+		BSET(res, tarr[i]);
 	for (; i<nt; i++) {
-		slot(tmp[i]);
+		slot(tarr[i]);
 		if (curi)
-			emit(OLoad, SYM(tmp[i]), slot(tmp[i]), R);
+			emit(OLoad, TMP(tarr[i]), slot(tarr[i]), R);
 	}
 	return res;
 }
@@ -240,13 +235,20 @@ setloc(Ref *pr, Bits *v, Bits *w)
 	 *   't' to 'w' before calling
 	 *   limit
 	 */
-	if (rtype(*pr) != RSym)
+	if (rtype(*pr) == RReg) {
+		nreg -= !BGET(br, pr->val);
+		BSET(br, pr->val);
+	}
+	if (rtype(*pr) != RTmp)
 		return;
 	t = pr->val;
 	BSET(*v, t);
-	*v = limit(v, NReg, w);
+	*v = limit(v, nreg, w);
 	if (curi->op == OLoad)
 	if (curi->to.val == t)
+		/* if t was spilled by limit,
+		 * it was not live so we don't
+		 * have to reload it */
 		curi++;
 	if (!BGET(*v, t))
 		*pr = slot(t);
@@ -279,13 +281,15 @@ spill(Fn *fn)
 	Phi *p;
 
 	ns = 0;
-	sym = fn->sym;
+	tmp = fn->tmp;
 	ntmp = fn->ntmp;
 	assert(ntmp < NBit*BITS);
 
 	for (n=fn->nblk-1; n>=0; n--) {
 		/* invariant: m>n => in,out of m updated */
 		b = fn->rpo[n];
+		nreg = NReg;
+		assert(bcnt(&br) == 0);
 
 		/* 1. find temporaries in registers at
 		 * the end of the block (put them in v) */
@@ -305,16 +309,16 @@ spill(Fn *fn)
 			for (z=0; z<BITS; z++)
 				v.t[z] = hd->gen.t[z] & b->out.t[z];
 			j = bcnt(&v);
-			if (j < NReg) {
+			if (j < nreg) {
 				w = b->out;
 				for (z=0; z<BITS; z++)
 					w.t[z] &= ~v.t[z];
 				j = bcnt(&w);   /* live through */
-				w = limit(&w, NReg - (l - j), 0);
+				w = limit(&w, nreg - (l - j), 0);
 				for (z=0; z<BITS; z++)
 					v.t[z] |= w.t[z];
-			} else if (j > NReg)
-				v = limit(&v, NReg, 0);
+			} else if (j > nreg)
+				v = limit(&v, nreg, 0);
 		} else if (s1) {
 			v = s1->in;
 			w = s1->in;
@@ -323,16 +327,16 @@ spill(Fn *fn)
 					v.t[z] |= s2->in.t[z];
 					w.t[z] &= s2->in.t[z];
 				}
-			assert(bcnt(&w) <= NReg);
-			v = limit(&v, NReg, &w);
+			assert(bcnt(&w) <= nreg);
+			v = limit(&v, nreg, &w);
 		}
 		b->out = v;
-		assert(bcnt(&v) <= NReg);
+		assert(bcnt(&v) <= nreg);
 
 		/* 2. process the block instructions */
-		if (rtype(b->jmp.arg) == RSym) {
+		if (rtype(b->jmp.arg) == RTmp) {
 			j = b->jmp.arg.val;
-			if (!BGET(v, j) && l==NReg) {
+			if (!BGET(v, j) && l==nreg) {
 				v = limit(&v, l-1, 0);
 				b->out = v;
 			}
@@ -340,20 +344,32 @@ spill(Fn *fn)
 		}
 		curi = &insb[NIns];
 		for (i=&b->ins[b->nins]; i!=b->ins;) {
-			assert(bcnt(&v) <= NReg);
+			assert(bcnt(&v) <= nreg);
 			i--;
-			if (!req(i->to, R)) {
-				assert(rtype(i->to)==RSym);
+			s = 0;
+			switch (rtype(i->to)) {
+			default:
+				assert(!"unhandled destination");
+			case RTmp:
 				j = i->to.val;
 				if (BGET(v, j))
 					BCLR(v, j);
 				else
 					v = limit(&v, NReg-1, &w);
-				s = sym[j].spill;
-			} else
-				s = 0;
+				s = tmp[j].spill;
+				break;
+			case RReg:
+				j = i->to.val;
+				if (BGET(br, j)) {
+					BCLR(br, j);
+					nreg++;
+				} else
+					v = limit(&v, nreg-1, &w);
+				break;
+			case -1:;
+			}
 			w = (Bits){{0}};
-			if (rtype(i->arg[1]) == RSym
+			if (rtype(i->arg[1]) == RTmp
 			&& !req(i->to, R)
 			&& opdesc[i->op].comm == F) {
 				/* <arch>
@@ -376,20 +392,21 @@ spill(Fn *fn)
 		}
 
 		for (p=b->phi; p; p=p->link) {
+			assert(rtype(p->to) == RTmp);
 			t = p->to.val;
 			if (BGET(v, t)) {
 				BCLR(v, t);
-				s = sym[t].spill;
+				s = tmp[t].spill;
 				if (s)
 					emit(OStore, R, p->to, SLOT(s));
 			} else
 				p->to = slot(p->to.val);
 		}
+		b->in = v;
 		free(b->ins);
 		b->nins = &insb[NIns] - curi;
 		b->ins = alloc(b->nins * sizeof(Ins));
 		memcpy(b->ins, curi, b->nins * sizeof(Ins));
-		b->in = v;
 	}
 	fn->nspill = ns;
 }