1 files changed, 14 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 4c864ca..cb352a5 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -2596,7 +2596,15 @@ void MachineBlockPlacement::rotateLoopWithProfile(
 /// otherwise, collect all blocks in the loop.
 MachineBlockPlacement::BlockFilterSet
 MachineBlockPlacement::collectLoopBlockSet(const MachineLoop &L) {
-  BlockFilterSet LoopBlockSet;
+  // Collect the blocks in a set ordered by block number, as this gives the same
+  // order as they appear in the function.
+  struct MBBCompare {
+    bool operator()(const MachineBasicBlock *X,
+                    const MachineBasicBlock *Y) const {
+      return X->getNumber() < Y->getNumber();
+    }
+  };
+  std::set<const MachineBasicBlock *, MBBCompare> LoopBlockSet;
 
   // Filter cold blocks off from LoopBlockSet when profile data is available.
   // Collect the sum of frequencies of incoming edges to the loop header from
@@ -2627,7 +2635,11 @@ MachineBlockPlacement::collectLoopBlockSet(const MachineLoop &L) {
   } else
     LoopBlockSet.insert(L.block_begin(), L.block_end());
 
-  return LoopBlockSet;
+  // Copy the blocks into a BlockFilterSet, as iterating it is faster than
+  // std::set. We will only remove blocks and never insert them, which will
+  // preserve the ordering.
+  BlockFilterSet Ret(LoopBlockSet.begin(), LoopBlockSet.end());
+  return Ret;
 }
 
 /// Forms basic block chains from the natural loop structures.