Fix loop parent computation in DataFlow.Graph (#2522)

This fixes the parent-child relationship computation in `DataFlow.Graph`
when there is a loop. This wasn't discovered until now because this is
used in Souperify and Souperify only runs after Flatten pass, which
produces redundant blocks between inside and outside of a loop.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/dataflow/graph.h b/src/dataflow/graph.h
index 873c4f218..41b145ee9 100644
--- a/src/dataflow/graph.h
+++ b/src/dataflow/graph.h
@@ -278,6 +278,9 @@ struct Graph : public UnifiedExpressionVisitor<Graph, Node*> {
     return &bad;
   }
   Node* doVisitLoop(Loop* curr) {
+    auto* oldParent = parent;
+    expressionParentMap[curr] = oldParent;
+    parent = curr;
     // As in Souper's LLVM extractor, we avoid loop phis, as we don't want
     // our traces to represent a value that differs across loop iterations.
     // For example,