1 files changed, 13 insertions, 3 deletions
diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 81aaca02a4d..0c29c76309e 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -736,9 +736,19 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
                          ++MachineBasicBlock::iterator(DbgMI));
   }
 
-  // Conservatively, clear any kill flags, since it's possible that they are no
-  // longer correct.
-  MI->clearKillInfo();
+  // When sinking the instruction the live time of its operands can be extended
+  // bejond their original last use (marked with a kill flag). Conservatively
+  // clear the kill flag in all instructions that use the same operand
+  // registers.
+  for (auto &MO : MI->uses())
+    if (MO.isReg() && MO.isUse()) {
+      // Preserve the kill flag for this instruction.
+      bool IsKill = MO.isKill();
+      // Clear the kill flag in all instruction that use this operand.
+      MRI->clearKillFlags(MO.getReg());
+      // Restore the kill flag for only this instruction.
+      MO.setIsKill(IsKill);
+    }
 
   return true;
 }