do not account for interferences in phi classes

Before this commit, I tried to make sure that
two interfering temporaries never ended up in
the same phi class.

This was to make sure that their register hints
were not counterproductively stepping on each
other's toes.  The idea is fine, but:

  * the implementation is clumsy because it
    mixes the orthogonal concepts of
    (i) interference and (ii) phi classes;

  * the hinting process in the register
    allocator is hard to understand because
    the disjoint-set data structure used for
    phi classes is cut in arbitrary places.

After this commit, the phi classes *really* are
phi classes represented with a proper disjoint-set
data structure.

live.c

@@ -19,46 +19,13 @@ liveon(BSet *v, Blk *b, Blk *s)
 			}
 }
 
-static int
-phitmp(int t, Tmp *tmp)
-{
-	int tp;
-
-	tp = tmp[t].phi;
-	return tp ? tp : t;
-}
-
-static void
-phifix(int t1, int *phi, Tmp *tmp)
-{
-	int t, t2;
-
-	/* detect temporaries arguments
-	 * of the same phi node that
-	 * interfere and separate them
-	 */
-	t = phitmp(t1, tmp);
-	t2 = phi[t];
-	if (t2 && t2 != t1) {
-		if (t != t1) {
-			tmp[t1].phi = t1;
-			t = t1;
-		} else {
-			tmp[t2].phi = t2;
-			phi[t2] = t2;
-		}
-	}
-	phi[t] = t1;
-}
-
 static void
-bset(Ref r, Blk *b, int *nlv, int *phi, Tmp *tmp)
+bset(Ref r, Blk *b, int *nlv, Tmp *tmp)
 {
 
 	if (rtype(r) != RTmp)
 		return;
 	bsset(b->gen, r.val);
-	phifix(r.val, phi, tmp);
 	if (!bshas(b->in, r.val)) {
 		nlv[KBASE(tmp[r.val].cls)]++;
 		bsset(b->in, r.val);
@@ -74,13 +41,11 @@ filllive(Fn *f)
 	Blk *b;
 	Ins *i;
 	int k, t, m[2], n, chg, nlv[2];
-	int *phi;
 	BSet u[1], v[1];
 	Mem *ma;
 
 	bsinit(u, f->ntmp);
 	bsinit(v, f->ntmp);
-	phi = emalloc(f->ntmp * sizeof phi[0]);
 	for (b=f->start; b; b=b->link) {
 		bsinit(b->in, f->ntmp);
 		bsinit(b->out, f->ntmp);
@@ -102,21 +67,18 @@ Again:
 		}
 		chg |= !bsequal(b->out, u);
 
-		memset(phi, 0, f->ntmp * sizeof phi[0]);
 		memset(nlv, 0, sizeof nlv);
 		b->out->t[0] |= T.rglob;
 		bscopy(b->in, b->out);
-		for (t=0; bsiter(b->in, &t); t++) {
-			phifix(t, phi, f->tmp);
+		for (t=0; bsiter(b->in, &t); t++)
 			nlv[KBASE(f->tmp[t].cls)]++;
-		}
 		if (rtype(b->jmp.arg) == RCall) {
 			assert((int)bscount(b->in) == T.nrglob &&
 				nlv[0] == T.nrglob &&
 				nlv[1] == 0);
 			b->in->t[0] |= T.retregs(b->jmp.arg, nlv);
 		} else
-			bset(b->jmp.arg, b, nlv, phi, f->tmp);
+			bset(b->jmp.arg, b, nlv, f->tmp);
 		for (k=0; k<2; k++)
 			b->nlive[k] = nlv[k];
 		for (i=&b->ins[b->nins]; i!=b->ins;) {
@@ -145,17 +107,16 @@ Again:
 					nlv[KBASE(f->tmp[t].cls)]--;
 				bsset(b->gen, t);
 				bsclr(b->in, t);
-				phi[phitmp(t, f->tmp)] = 0;
 			}
 			for (k=0; k<2; k++)
 				switch (rtype(i->arg[k])) {
 				case RMem:
 					ma = &f->mem[i->arg[k].val];
-					bset(ma->base, b, nlv, phi, f->tmp);
-					bset(ma->index, b, nlv, phi, f->tmp);
+					bset(ma->base, b, nlv, f->tmp);
+					bset(ma->index, b, nlv, f->tmp);
 					break;
 				default:
-					bset(i->arg[k], b, nlv, phi, f->tmp);
+					bset(i->arg[k], b, nlv, f->tmp);
 					break;
 				}
 			for (k=0; k<2; k++)
@@ -167,7 +128,6 @@ Again:
 		chg = 0;
 		goto Again;
 	}
-	free(phi);
 
 	if (debug['L']) {
 		fprintf(stderr, "\n> Liveness analysis:\n");

ssa.c

@@ -40,7 +40,7 @@ filluse(Fn *fn)
 	Blk *b;
 	Phi *p;
 	Ins *i;
-	int m, t, w;
+	int m, t, tp, w;
 	uint a;
 	Tmp *tmp;
 
@@ -49,8 +49,8 @@ filluse(Fn *fn)
 	for (t=Tmp0; t<fn->ntmp; t++) {
 		tmp[t].ndef = 0;
 		tmp[t].nuse = 0;
-		tmp[t].phi = 0;
 		tmp[t].cls = 0;
+		tmp[t].phi = 0;
 		tmp[t].width = WFull;
 		if (tmp[t].use == 0)
 			tmp[t].use = vnew(0, sizeof(Use), Pfn);
@@ -58,16 +58,17 @@ filluse(Fn *fn)
 	for (b=fn->start; b; b=b->link) {
 		for (p=b->phi; p; p=p->link) {
 			assert(rtype(p->to) == RTmp);
-			t = p->to.val;
-			tmp[t].ndef++;
-			tmp[t].cls = p->cls;
-			tmp[t].phi = p->to.val;
+			tp = p->to.val;
+			tmp[tp].ndef++;
+			tmp[tp].cls = p->cls;
+			tp = phicls(tp, fn->tmp);
 			for (a=0; a<p->narg; a++)
 				if (rtype(p->arg[a]) == RTmp) {
 					t = p->arg[a].val;
 					adduse(&tmp[t], UPhi, b, p);
-					if (!tmp[t].phi)
-						tmp[t].phi = p->to.val;
+					t = phicls(t, fn->tmp);
+					if (t != tp)
+						tmp[t].phi = tp;
 				}
 		}
 		for (i=b->ins; i-b->ins < b->nins; i++) {

util.c

@@ -249,24 +249,16 @@ clsmerge(short *pk, short k)
 }
 
 int
-phicls(int t, Tmp *tmp /*, int c*/)
+phicls(int t, Tmp *tmp)
 {
-	if (tmp[t].phi)
-		return tmp[t].phi;
-	return t;
-#if 0
 	int t1;
 
 	t1 = tmp[t].phi;
 	if (!t1)
-		t1 = t;
-	if (t != t1) {
-		t1 = phitmp(t1, tmp, c);
-		if (c)
-			tmp[t].phi = t1;
-	}
+		return t;
+	t1 = phicls(t1, tmp);
+	tmp[t].phi = t1;
 	return t1;
-#endif
 }
 
 Ref