cfg: allow dead blocks with alloca pseudo instrs

1 files changed, 7 insertions, 2 deletions

diff --git a/ir/cfg.c b/ir/cfg.c
index df428d1..8e86cb2 100644
--- a/ir/cfg.c
+++ b/ir/cfg.c
@@ -24,14 +24,19 @@ sortrpo(struct function *fn)
    fn->entry->id = 0;
    porec(&rpo, fn->entry);
    ndead = rpo - rpobuf;
-   for (struct block *blk = fn->entry->lprev, *next; ndead > 0; blk = next) {
+   for (struct block *blk = fn->entry->lprev, *next; blk != fn->entry; blk = next) {
       next = blk->lprev;
       if (!wasvisited(blk)) {
+         for (int i = 0; i < blk->ins.n; ++i) {
+            /* don't delete unreachable blocks with alloca pseudo-instrs */
+            if (oisalloca(instrtab[blk->ins.p[i]].op))
+               goto Next;
+         }
          for (int i = 0; i < blk->npred; ++i)
             assert(!wasvisited(blkpred(blk, i)));
-         blk->lnext = blk->lprev = NULL;
          freeblk(fn, blk);
          --ndead;
+      Next:;
       }
    }
    for (i = 1, ++rpo; rpo < rpoend; ++rpo, ++i) {