[llvm] 3ceea67 - [JITLink] Fix edge removal iterator invalidation.

[Lang Hames via llvm-commits]

Author: Lang Hames
Date: 2020-04-22T14:16:46-07:00
New Revision: 3ceea67c091d556ec672e65ec4e9d72997e76807

URL: https://github.com/llvm/llvm-project/commit/3ceea67c091d556ec672e65ec4e9d72997e76807
DIFF: https://github.com/llvm/llvm-project/commit/3ceea67c091d556ec672e65ec4e9d72997e76807.diff

LOG: [JITLink] Fix edge removal iterator invalidation.

This patch changes Block::removeEdge to return a valid iterator to the new next
element, and uses this to update the edge removal algorithm in
LinkGraph::splitBlock.

Added: 
    

Modified: 
    llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
    llvm/lib/ExecutionEngine/JITLink/JITLink.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h b/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
index 967397f10ad3..000dd18fb373 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h
@@ -248,8 +248,8 @@ class Block : public Addressable {
   bool edges_empty() const { return Edges.empty(); }
 
   /// Remove the edge pointed to by the given iterator.
-  /// Invalidates all iterators that point to or past the given one.
-  void removeEdge(const_edge_iterator I) { Edges.erase(I); }
+  /// Returns an iterator to the new next element.
+  edge_iterator removeEdge(edge_iterator I) { return Edges.erase(I); }
 
 private:
   static constexpr uint64_t MaxAlignmentOffset = (1ULL << 57) - 1;

diff  --git a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
index 6c924f889577..c60076e02afa 100644
--- a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
@@ -180,18 +180,14 @@ Block &LinkGraph::splitBlock(Block &B, size_t SplitIndex,
     // Copy edges to NewBlock (recording their iterators so that we can remove
     // them from B), and update of Edges remaining on B.
     std::vector<Block::edge_iterator> EdgesToRemove;
-    for (auto I = B.edges().begin(), E = B.edges().end(); I != E; ++I) {
+    for (auto I = B.edges().begin(); I != B.edges().end();) {
       if (I->getOffset() < SplitIndex) {
         NewBlock.addEdge(*I);
-        EdgesToRemove.push_back(I);
-      } else
+        I = B.removeEdge(I);
+      } else {
         I->setOffset(I->getOffset() - SplitIndex);
-    }
-
-    // Remove edges that were transfered to NewBlock from B.
-    while (!EdgesToRemove.empty()) {
-      B.removeEdge(EdgesToRemove.back());
-      EdgesToRemove.pop_back();
+        ++I;
+      }
     }
   }