2 files changed, 22 insertions, 0 deletions
diff --git a/ir/ir.c b/ir/ir.c
index 412d0f9..4a092b3 100644
--- a/ir/ir.c
+++ b/ir/ir.c
@@ -451,6 +451,27 @@ numberinstrs(struct function *fn)
    } while ((blk = blk->lnext) != fn->entry);
 }
 
+static bool
+reachablerec(struct function *fn, struct block *blk)
+{
+   if (blk == fn->entry) return 1;
+   markvisited(blk);
+   if (blk->npred == 1 && !wasvisited(blkpred(blk, 0)))
+      return reachablerec(fn, blkpred(blk, 0));
+   else for (int i = 0; i < blk->npred; ++i) {
+      struct block *p = blkpred(blk, i);
+      if (!wasvisited(p) && reachablerec(fn, p)) return 1;
+   }
+   return 0;
+}
+
+bool
+blkreachable(struct function *fn, struct block *blk)
+{
+   startbbvisit();
+   return reachablerec(fn, blk);
+}
+
 /* require use */
 void
 replcuses(union ref from, union ref to)
diff --git a/ir/ir.h b/ir/ir.h
index 77f25d4..9047233 100644
--- a/ir/ir.h
+++ b/ir/ir.h
@@ -277,6 +277,7 @@ void fillblkids(struct function *);
 #define wasvisited(blk) ((blk)->visit == visitmark)
 #define markvisited(blk) ((blk)->visit = visitmark)
 void numberinstrs(struct function *);
+bool blkreachable(struct function *fn, struct block *blk);
 
 /** builder.c **/
 union ref irbinop(struct function *, enum op, enum irclass, union ref lhs, union ref rhs);