From af760942e7d9d215a51cdb6d18993cdead70c9f6 Mon Sep 17 00:00:00 2001
From: Pietro Fezzardi <pietro@rev.ng>
Date: Tue, 14 Jun 2022 12:06:39 +0200
Subject: [PATCH] DLATypeSystem: add API to move edge target

---
 .../DataLayoutAnalysis/DLATypeSystem.h        |  9 ++--
 lib/DataLayoutAnalysis/DLATypeSystem.cpp      | 44 +++++++++----------
 .../DLAComputeNonInterferingComponents.cpp    |  2 +-
 3 files changed, 26 insertions(+), 29 deletions(-)

diff --git a/include/revng-c/DataLayoutAnalysis/DLATypeSystem.h b/include/revng-c/DataLayoutAnalysis/DLATypeSystem.h
index fca7bc092..525c02fdd 100644
--- a/include/revng-c/DataLayoutAnalysis/DLATypeSystem.h
+++ b/include/revng-c/DataLayoutAnalysis/DLATypeSystem.h
@@ -119,6 +119,7 @@ struct LayoutTypeSystemNode {
   const uint64_t ID = 0ULL;
   using Link = std::pair<LayoutTypeSystemNode *, const TypeLinkTag *>;
   using NeighborsSet = std::set<Link>;
+  using NeighborIterator = NeighborsSet::iterator;
   NeighborsSet Successors{};
   NeighborsSet Predecessors{};
   uint64_t Size{};
@@ -287,10 +288,10 @@ public:
 
   void removeNode(LayoutTypeSystemNode *N);
 
-  void moveEdge(LayoutTypeSystemNode *OldSrc,
-                LayoutTypeSystemNode *NewSrc,
-                LayoutTypeSystemNode::NeighborsSet::iterator EdgeIt,
-                int64_t OffsetToSum);
+  void moveEdgeSource(LayoutTypeSystemNode *OldSrc,
+                      LayoutTypeSystemNode *NewSrc,
+                      LayoutTypeSystemNode::NeighborIterator EdgeIt,
+                      int64_t OffsetToSum);
 
 private:
   uint64_t NID = 0ULL;
diff --git a/lib/DataLayoutAnalysis/DLATypeSystem.cpp b/lib/DataLayoutAnalysis/DLATypeSystem.cpp
index 82c0c1081..931b1ac94 100644
--- a/lib/DataLayoutAnalysis/DLATypeSystem.cpp
+++ b/lib/DataLayoutAnalysis/DLATypeSystem.cpp
@@ -321,47 +321,47 @@ void LayoutTypeSystem::removeNode(LayoutTypeSystemNode *ToRemove) {
   NodeAllocator.Deallocate(ToRemove);
 }
 
-using NeighborIterator = LayoutTypeSystemNode::NeighborsSet::iterator;
+using NeighborIterator = LayoutTypeSystemNode::NeighborIterator;
 
-static void moveEdgeWithoutSumming(LayoutTypeSystemNode *OldSrc,
-                                   LayoutTypeSystemNode *NewSrc,
-                                   NeighborIterator EdgeIt) {
 
-  // First, move successor edge from OldSrc to NewSrc
-  auto SuccHandle = OldSrc->Successors.extract(EdgeIt);
-  revng_assert(not SuccHandle.empty());
-  NewSrc->Successors.insert(std::move(SuccHandle));
-
-  // Then, move predecessor edge from OldSrc to NewSrc
+static void moveEdgeSourceWithoutSumming(LayoutTypeSystemNode *OldSrc,
+                                         LayoutTypeSystemNode *NewSrc,
+                                         NeighborIterator EdgeIt) {
+  // First, move the predecessor edge from OldSrc to NewSrc.
   LayoutTypeSystemNode *Tgt = EdgeIt->first;
   auto PredHandle = Tgt->Predecessors.extract({ OldSrc, EdgeIt->second });
   revng_assert(not PredHandle.empty());
   PredHandle.value().first = NewSrc;
   Tgt->Predecessors.insert(std::move(PredHandle));
+
+  // Then, move the successor edge from OldSrc to NewSrc
+  auto SuccHandle = OldSrc->Successors.extract(EdgeIt);
+  revng_assert(not SuccHandle.empty());
+  NewSrc->Successors.insert(std::move(SuccHandle));
 }
 
-void LayoutTypeSystem::moveEdge(LayoutTypeSystemNode *OldSrc,
-                                LayoutTypeSystemNode *NewSrc,
-                                NeighborIterator EdgeIt,
-                                int64_t OffsetToSum) {
+void LayoutTypeSystem::moveEdgeSource(LayoutTypeSystemNode *OldSrc,
+                                      LayoutTypeSystemNode *NewSrc,
+                                      NeighborIterator EdgeIt,
+                                      int64_t OffsetToSum) {
 
   if (not OldSrc or not NewSrc)
     return;
 
   if (not OffsetToSum)
-    return moveEdgeWithoutSumming(OldSrc, NewSrc, EdgeIt);
+    return moveEdgeSourceWithoutSumming(OldSrc, NewSrc, EdgeIt);
 
   LayoutTypeSystemNode *Tgt = EdgeIt->first;
 
-  // First, move successor edges from OldSrc to NewSrc
+  // Erase info in Tgt that represent the fact that OldSrc was a predecessor.
+  bool Erased = Tgt->Predecessors.erase({ OldSrc, EdgeIt->second });
+  revng_assert(Erased);
+
+  // Extract the successor edge to be moved from OldSrc to NewSrc
   auto OldSuccHandle = OldSrc->Successors.extract(EdgeIt);
   revng_assert(not OldSuccHandle.empty());
 
   // Add new instance links with adjusted offsets from NewSrc to Tgt.
-  // Using the addInstanceLink methods already marks injects NewSrc among the
-  // predecessors of Tgt, so after this we only need to remove OldSrc from
-  // Tgt's predecessors and we're done.
-
   const TypeLinkTag *EdgeTag = OldSuccHandle.value().second;
   switch (EdgeTag->getKind()) {
 
@@ -377,10 +377,6 @@ void LayoutTypeSystem::moveEdge(LayoutTypeSystemNode *OldSrc,
   default:
     revng_unreachable("unexpected edge kind");
   }
-
-  // Then, remove all the remaining info in Tgt that represent the fact that
-  // OldSrc was a predecessor.
-  auto PredHandle = Tgt->Predecessors.extract({ OldSrc, EdgeIt->second });
 }
 
 static Logger<> VerifyDLALog("dla-verify-strict");
diff --git a/lib/DataLayoutAnalysis/Middleend/DLAComputeNonInterferingComponents.cpp b/lib/DataLayoutAnalysis/Middleend/DLAComputeNonInterferingComponents.cpp
index 18459e12d..eedf8494f 100644
--- a/lib/DataLayoutAnalysis/Middleend/DLAComputeNonInterferingComponents.cpp
+++ b/lib/DataLayoutAnalysis/Middleend/DLAComputeNonInterferingComponents.cpp
@@ -224,7 +224,7 @@ bool ComputeNonInterferingComponents::runOnTypeSystem(LayoutTypeSystem &TS) {
         using llvm::iterator_range;
         auto OrderedChildRange = iterator_range(C.StartChildIt, C.EndChildIt);
         for (auto &OrderedChild : OrderedChildRange)
-          TS.moveEdge(N, New, OrderedChild.ChildIt, -C.StartByte);
+          TS.moveEdgeSource(N, New, OrderedChild.ChildIt, -C.StartByte);
 
         // Add a link between N and the New node representing the component.
         // The component is at offset C.StartByte inside N.