path: root/legacy/llvm8/scc-insertion.patch

From f7e9f4f4c50245d10ca9869a9f8f3d431dfb6948 Mon Sep 17 00:00:00 2001
From: Warren Ristow <warren_ristow@playstation.sony.com>
Date: Tue, 14 Jan 2020 10:30:24 -0800
Subject: [PATCH] SCC: Allow ReplaceNode to safely support insertion

If scc_iterator::ReplaceNode is inserting a new entry in the map,
rather than replacing an existing entry, the possibility of growing
the map could cause a failure.  This change safely implements the
insertion.

Reviewed By: probinson

Differential Revision: https://reviews.llvm.org/D72469
---
 include/llvm/ADT/SCCIterator.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/llvm/ADT/SCCIterator.h b/include/llvm/ADT/SCCIterator.h
index eb1a5d0938cf..1e642b9f75d3 100644
--- a/include/llvm/ADT/SCCIterator.h
+++ b/include/llvm/ADT/SCCIterator.h
@@ -134,7 +134,10 @@ class scc_iterator : public iterator_facade_base<
   /// has been deleted, and \c New is to be used in its place.
   void ReplaceNode(NodeRef Old, NodeRef New) {
     assert(nodeVisitNumbers.count(Old) && "Old not in scc_iterator?");
-    nodeVisitNumbers[New] = nodeVisitNumbers[Old];
+    // Do the assignment in two steps, in case 'New' is not yet in the map, and
+    // inserting it causes the map to grow.
+    auto tempVal = nodeVisitNumbers[Old];
+    nodeVisitNumbers[New] = tempVal;
     nodeVisitNumbers.erase(Old);
   }
 };