1 files changed, 9 insertions, 35 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
index 5601678734a..c006f3cc2ef 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
@@ -352,43 +352,17 @@ void llvm::calculateDbgEntityHistory(const MachineFunction *MF,
       }
     }
 
-    // Make sure locations for all variables are valid only until the end of
-    // the basic block (unless it's the last basic block, in which case let
-    // their liveness run off to the end of the function).
+    // Make sure locations for register-described variables are valid only
+    // until the end of the basic block (unless it's the last basic block, in
+    // which case let their liveness run off to the end of the function).
     if (!MBB.empty() && &MBB != &MF->back()) {
-      // Iterate over all variables that have open debug values.
-      SmallSet<unsigned, 8> RegsToClobber;
-      for (auto &Pair : LiveEntries) {
-        // Iterate over history entries for all open fragments.
-        SmallVector<EntryIndex, 8> IdxesToRemove;
-        for (EntryIndex Idx : Pair.second) {
-          DbgValueHistoryMap::Entry &Ent = DbgValues.getEntry(Pair.first, Idx);
-          assert(Ent.isDbgValue() && !Ent.isClosed());
-          const MachineInstr *DbgValue = Ent.getInstr();
-
-          // If this is a register or indirect DBG_VALUE, apply some futher
-          // tests to see if we should clobber it. Perform the clobbering
-          // later though, to keep LiveEntries iteration stable.
-          if (DbgValue->getOperand(0).isReg()) {
-            unsigned RegNo = DbgValue->getOperand(0).getReg();
-            if (TRI->isVirtualRegister(RegNo) || ChangingRegs.test(RegNo))
-              RegsToClobber.insert(RegNo);
-          } else {
-            // This is a constant, terminate it at end of the block. Store
-            // eliminated EntryIdx and delete later, for iteration stability.
-            EntryIndex ClobIdx = DbgValues.startClobber(Pair.first, MBB.back());
-            DbgValues.getEntry(Pair.first, Idx).endEntry(ClobIdx);
-            IdxesToRemove.push_back(Idx);
-          }
-        }
-
-        for (EntryIndex Idx : IdxesToRemove)
-          Pair.second.erase(Idx);
+      for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
+        auto CurElem = I++; // CurElem can be erased below.
+        if (TRI->isVirtualRegister(CurElem->first) ||
+            ChangingRegs.test(CurElem->first))
+          clobberRegisterUses(RegVars, CurElem, DbgValues, LiveEntries,
+                              MBB.back());
       }
-
-      // Implement clobbering of registers at the end of BB.
-      for (unsigned Reg : RegsToClobber)
-        clobberRegisterUses(RegVars, Reg, DbgValues, LiveEntries, MBB.back());
     }
   }
 }