Fix for InlineSpiller accessing not updated dom tree base information.

Summary:
The InlineSpiller was accessing the DominatorTreeBase directly
through the public data member DT in the MachineDominatorTree.
This is not a good idea as the "cached" information in
SplitCriticalEdges is not applied before the access.
The DominatorTreeBase must be accessed through the member
function getBase() in MachineDominatorTree.

The fault was introduced in r266162.

I think the public data member DT in the MachineDominatorTree
should have been made private in the original code (r215576)
that introduced the concept of lazily updating the
MachineDominatorTree information from
MachineBasicBlock::SplitCriticalEdge().

Patch by Karl-Johan Karlsson <karl-johan.karlsson@ericsson.com>

Reviewers: wmi, qcolombet

Subscribers: llvm-commits, bjope, uabelho

Differential Revision: https://reviews.llvm.org/D27983

llvm-svn: 290950

2 files changed, 7 insertions, 5 deletions

diff --git a/llvm/include/llvm/CodeGen/MachineDominators.h b/llvm/include/llvm/CodeGen/MachineDominators.h
index 76e1df89169..21ecef587aa 100644
--- a/llvm/include/llvm/CodeGen/MachineDominators.h
+++ b/llvm/include/llvm/CodeGen/MachineDominators.h
@@ -59,6 +59,9 @@ class MachineDominatorTree : public MachineFunctionPass {
   /// such as BB == elt.NewBB.
   mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
 
+  /// The DominatorTreeBase that is used to compute a normal dominator tree
+  DominatorTreeBase<MachineBasicBlock>* DT;
+
   /// \brief Apply all the recorded critical edges to the DT.
   /// This updates the underlying DT information in a way that uses
   /// the fast query path of DT as much as possible.
@@ -68,7 +71,6 @@ class MachineDominatorTree : public MachineFunctionPass {
 
 public:
   static char ID; // Pass ID, replacement for typeid
-  DominatorTreeBase<MachineBasicBlock>* DT;
 
   MachineDominatorTree();
 
diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 422f2dc2f2f..3d81184f774 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -1124,7 +1124,7 @@ void HoistSpillHelper::rmRedundantSpills(
   // earlier spill with smaller SlotIndex.
   for (const auto CurrentSpill : Spills) {
     MachineBasicBlock *Block = CurrentSpill->getParent();
-    MachineDomTreeNode *Node = MDT.DT->getNode(Block);
+    MachineDomTreeNode *Node = MDT.getBase().getNode(Block);
     MachineInstr *PrevSpill = SpillBBToSpill[Node];
     if (PrevSpill) {
       SlotIndex PIdx = LIS.getInstructionIndex(*PrevSpill);
@@ -1132,9 +1132,9 @@ void HoistSpillHelper::rmRedundantSpills(
       MachineInstr *SpillToRm = (CIdx > PIdx) ? CurrentSpill : PrevSpill;
       MachineInstr *SpillToKeep = (CIdx > PIdx) ? PrevSpill : CurrentSpill;
       SpillsToRm.push_back(SpillToRm);
-      SpillBBToSpill[MDT.DT->getNode(Block)] = SpillToKeep;
+      SpillBBToSpill[MDT.getBase().getNode(Block)] = SpillToKeep;
     } else {
-      SpillBBToSpill[MDT.DT->getNode(Block)] = CurrentSpill;
+      SpillBBToSpill[MDT.getBase().getNode(Block)] = CurrentSpill;
     }
   }
   for (const auto SpillToRm : SpillsToRm)
@@ -1209,7 +1209,7 @@ void HoistSpillHelper::getVisitOrders(
   // Sort the nodes in WorkSet in top-down order and save the nodes
   // in Orders. Orders will be used for hoisting in runHoistSpills.
   unsigned idx = 0;
-  Orders.push_back(MDT.DT->getNode(Root));
+  Orders.push_back(MDT.getBase().getNode(Root));
   do {
     MachineDomTreeNode *Node = Orders[idx++];
     const std::vector<MachineDomTreeNode *> &Children = Node->getChildren();