2 files changed, 19 insertions, 7 deletions

diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 1440b967aea..118836ecbf6 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -315,9 +315,18 @@ public:
 
   // LiveIn management methods.
 
-  /// addLiveIn - Add the specified register as a live in.  Note that it
-  /// is an error to add the same register to the same set more than once.
-  void addLiveIn(unsigned Reg)  { LiveIns.push_back(Reg); }
+  /// Adds the specified register as a live in. Note that it is an error to add
+  /// the same register to the same set more than once unless the intention is
+  /// to call sortUniqueLiveIns after all registers are added.
+  void addLiveIn(unsigned Reg) { LiveIns.push_back(Reg); }
+
+  /// Sorts and uniques the LiveIns vector. It can be significantly faster to do
+  /// this than repeatedly calling isLiveIn before calling addLiveIn for every
+  /// LiveIn insertion.
+  void sortUniqueLiveIns() {
+    std::sort(LiveIns.begin(), LiveIns.end());
+    LiveIns.erase(std::unique(LiveIns.begin(), LiveIns.end()), LiveIns.end());
+  }
 
   /// Add PhysReg as live in to this block, and ensure that there is a copy of
   /// PhysReg to a virtual register of class RC. Return the virtual register
diff --git a/llvm/lib/CodeGen/VirtRegMap.cpp b/llvm/lib/CodeGen/VirtRegMap.cpp
index d9adfdf7b2e..9fb1b5b65fb 100644
--- a/llvm/lib/CodeGen/VirtRegMap.cpp
+++ b/llvm/lib/CodeGen/VirtRegMap.cpp
@@ -264,8 +264,7 @@ void VirtRegRewriter::addMBBLiveIns() {
             if ((SubRegLaneMask & S.LaneMask) == 0)
               continue;
             for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
-              if (!LiveIn[i]->isLiveIn(SubReg))
-                LiveIn[i]->addLiveIn(SubReg);
+              LiveIn[i]->addLiveIn(SubReg);
             }
           }
           LiveIn.clear();
@@ -277,12 +276,16 @@ void VirtRegRewriter::addMBBLiveIns() {
         if (!Indexes->findLiveInMBBs(Seg.start, Seg.end, LiveIn))
           continue;
         for (unsigned i = 0, e = LiveIn.size(); i != e; ++i)
-          if (!LiveIn[i]->isLiveIn(PhysReg))
-            LiveIn[i]->addLiveIn(PhysReg);
+          LiveIn[i]->addLiveIn(PhysReg);
         LiveIn.clear();
       }
     }
   }
+
+  // Sort and unique MBB LiveIns as we've not checked if SubReg/PhysReg were in
+  // each MBB's LiveIns set before calling addLiveIn on them.
+  for (MachineBasicBlock &MBB : *MF)
+    MBB.sortUniqueLiveIns();
 }
 
 void VirtRegRewriter::rewrite() {