qbe

commit c81ed54562d223ab49be758075291432fe70ac58
parent 34b4e56ca46f763f72c3a8ef0d892c7d5bbc7132
Author: Quentin Carbonneaux <quentin.carbonneaux@yale.edu>
Date:   Mon,  9 Nov 2015 17:00:57 -0500

fix bug in frontier discovery

Diffstat:
M
lisc/ssa.c
 | 
12
+++++-------

1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/lisc/ssa.c b/lisc/ssa.c
@@ -148,7 +148,7 @@ filldom(Fn *fn)
 static int
 sdom(Blk *b1, Blk *b2)
 {
-	if (b1 == b2)
+	if (!b2 || b1 == b2)
 		return 0;
 	while (b2->id > b1->id)
 		b2 = b2->idom;
@@ -176,12 +176,10 @@ fillfron(Fn *fn)
 	Blk *a, *b;
 
 	for (b=fn->start; b; b=b->link) {
-		if (b->s1)
-			for (a=b; !sdom(a, b->s1); a=a->link)
-				addfron(a, b->s1);
-		if (b->s2)
-			for (a=b; !sdom(a, b->s2); a=a->link)
-				addfron(a, b->s2);
+		for (a=b; !sdom(a, b->s1); a=a->idom)
+			addfron(a, b->s1);
+		for (a=b; !sdom(a, b->s2); a=a->idom)
+			addfron(a, b->s2);
 	}
 }