make phi-class handling more local

The phi classes are no longer in a union-find
structure, instead each temporary argument of
a phi node gets a pointer to it.  The hinting
of the phi node is then shared with its the
one of its arguments.  When liveness proceeds
and finds out that two elements with same
hinting (a phi node and one of its arguments
or two arguments of the same phi node)
interfere, one of them has its phi pointer
reset, that way, the hinting won't be shared.

6 files changed, 23 insertions, 59 deletions

diff --git a/lisc/lisc.h b/lisc/lisc.h
index 6a8d687..0912b1f 100644
--- a/lisc/lisc.h
+++ b/lisc/lisc.h
@@ -347,8 +347,6 @@ void printfn(Fn *, FILE *);
 /* ssa.c */
 void fillpreds(Fn *);
 void fillrpo(Fn *);
-int phirepr(Tmp *, int);
-void fillphi(Fn *);
 void ssafix(Fn *, int);
 
 /* live.c */
diff --git a/lisc/live.c b/lisc/live.c
index 0e59d78..d355fd6 100644
--- a/lisc/live.c
+++ b/lisc/live.c
@@ -18,23 +18,32 @@ liveon(Blk *b, Blk *s)
 	return v;
 }
 
+static int
+phitmp(int t, Tmp *tmp)
+{
+	int tp;
+
+	tp = tmp[t].phi;
+	return tp ? tp : t;
+}
+
 static void
 phifix(int t1, short *phi, Tmp *tmp)
 {
 	int t, t2;
 
-	/* detect temporaries in the same
-	 * phi-class that interfere and
-	 * separate them
+	/* detect temporaries arguments
+	 * of the same phi node that
+	 * interfere and separate them
 	 */
-	t = phirepr(tmp, t1);
+	t = phitmp(t1, tmp);
 	t2 = phi[t];
 	if (t2 && t2 != t1) {
-		if (tmp[t1].phi != t1) {
-			tmp[t1].phi = t1;
+		if (t != t1) {
+			tmp[t1].phi = 0;
 			t = t1;
 		} else {
-			tmp[t2].phi = t2;
+			tmp[t2].phi = 0;
 			phi[t2] = t2;
 		}
 	}
@@ -115,7 +124,7 @@ Again:
 				nlv -= BGET(b->in, i->to.val);
 				BSET(b->gen, i->to.val);
 				BCLR(b->in, i->to.val);
-				t = phirepr(f->tmp, i->to.val);
+				t = phitmp(i->to.val, f->tmp);
 				phi[t] = 0;
 			}
 			for (m=0; m<2; m++)
diff --git a/lisc/main.c b/lisc/main.c
index 3c6a009..b3389c4 100644
--- a/lisc/main.c
+++ b/lisc/main.c
@@ -50,7 +50,6 @@ func(Fn *fn)
 	isel(fn);
 	fillrpo(fn);
 	fillpreds(fn);
-	fillphi(fn);
 	filllive(fn);
 	fillcost(fn);
 	spill(fn);
diff --git a/lisc/parse.c b/lisc/parse.c
index 8b6f697..35f6d78 100644
--- a/lisc/parse.c
+++ b/lisc/parse.c
@@ -547,6 +547,8 @@ DoOp:
 			arg[i] = parseref();
 			if (req(arg[i], R))
 				err("invalid instruction argument");
+			if (op == -1 && rtype(arg[i]) == RTmp)
+				tmp[arg[i].val].phi = r.val;
 			i++;
 			t = peek();
 			if (t == TNL)
diff --git a/lisc/rega.c b/lisc/rega.c
index 628f7e8..8d1bb1a 100644
--- a/lisc/rega.c
+++ b/lisc/rega.c
@@ -25,8 +25,10 @@ static int cpm, npm;   /* capacity and size of pm */
 static int *
 hint(int t)
 {
-	t = phirepr(tmp, t);
-	return &tmp[t].hint;
+	if (tmp[t].phi)
+		return &tmp[tmp[t].phi].hint;
+	else
+		return &tmp[t].hint;
 }
 
 static int
diff --git a/lisc/ssa.c b/lisc/ssa.c
index 97003e0..5d89b90 100644
--- a/lisc/ssa.c
+++ b/lisc/ssa.c
@@ -87,52 +87,6 @@ fillrpo(Fn *f)
 	}
 }
 
-/* gets the representant for the phi class of t
- */
-int
-phirepr(Tmp *tmp, int t)
-{
-	int tp;
-
-	tp = tmp[t].phi;
-	if (tp == 0)
-		tp = t;
-	else if (tp != t) {
-		tp = phirepr(tmp, tp);
-		tmp[t].phi = tp;
-	}
-	return tp;
-}
-
-/* fill union find data for phi classes
- */
-void
-fillphi(Fn *fn)
-{
-	Blk *b;
-	Phi *p;
-	uint a;
-	int t, ta;
-	Tmp *tmp;
-
-	tmp = fn->tmp;
-	for (t=Tmp0; t<fn->ntmp; t++)
-		tmp[t].phi = 0;
-	for (b=fn->start; b; b=b->link)
-		for (p=b->phi; p; p=p->link) {
-			t = p->to.val;
-			if (tmp[t].phi == 0)
-				tmp[t].phi = t;
-			for (a=0; a<p->narg; a++) {
-				if (rtype(p->arg[a]) != RTmp)
-					continue;
-				ta = p->arg[a].val;
-				ta = phirepr(tmp, ta);
-				tmp[ta].phi = t;
-			}
-		}
-}
-
 static Ref *top, *bot;
 static Ref topdef(Blk *, Fn *, int);