1 files changed, 34 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp
index d56f113aa7f..d0f6f56b3d7 100644
--- a/llvm/lib/CodeGen/MachineOutliner.cpp
+++ b/llvm/lib/CodeGen/MachineOutliner.cpp
@@ -1323,6 +1323,8 @@ MachineOutliner::createOutlinedFunction(Module &M, const OutlinedFunction &OF,
     DB.finalize();
   }
 
+  // Outlined functions shouldn't preserve liveness.
+  MF.getProperties().reset(MachineFunctionProperties::Property::TracksLiveness);
   MF.getRegInfo().freezeReservedRegs(MF);
   return &MF;
 }
@@ -1357,8 +1359,6 @@ bool MachineOutliner::outline(
     MachineBasicBlock::iterator EndIt = Mapper.InstrList[EndIdx];
     assert(EndIt != MBB->end() && "EndIt out of bounds!");
 
-    EndIt++; // Erase needs one past the end index.
-
     // Does this candidate have a function yet?
     if (!OF.MF) {
       OF.MF = createOutlinedFunction(M, OF, Mapper);
@@ -1401,10 +1401,40 @@ bool MachineOutliner::outline(
     const TargetInstrInfo &TII = *STI.getInstrInfo();
 
     // Insert a call to the new function and erase the old sequence.
-    TII.insertOutlinedCall(M, *MBB, StartIt, *MF, C.MInfo);
+    auto CallInst = TII.insertOutlinedCall(M, *MBB, StartIt, *MF, C.MInfo);
     StartIt = Mapper.InstrList[C.getStartIdx()];
-    MBB->erase(StartIt, EndIt);
 
+    // If the caller tracks liveness, then we need to make sure that anything
+    // we outline doesn't break liveness assumptions.
+    // The outlined functions themselves currently don't track liveness, but
+    // we should make sure that the ranges we yank things out of aren't
+    // wrong.
+    if (MBB->getParent()->getProperties().hasProperty(
+            MachineFunctionProperties::Property::TracksLiveness)) {
+      // Helper lambda for adding implicit def operands to the call instruction.
+      auto CopyDefs = [&CallInst](MachineInstr &MI) {
+        for (MachineOperand &MOP : MI.operands()) {
+          // Skip over anything that isn't a register.
+          if (!MOP.isReg())
+            continue;
+
+          // If it's a def, add it to the call instruction.
+          if (MOP.isDef())
+            CallInst->addOperand(
+                MachineOperand::CreateReg(MOP.getReg(), true, /* isDef = true */
+                                          true /* isImp = true */));
+        }
+      };
+
+      // Copy over the defs in the outlined range.
+      // First inst in outlined range <-- Anything that's defined in this
+      // ...                           .. range has to be added as an implicit
+      // Last inst in outlined range  <-- def to the call instruction.
+      std::for_each(CallInst, EndIt, CopyDefs);
+    }
+
+    EndIt++; // Erase needs one past the end index.
+    MBB->erase(StartIt, EndIt);
     OutlinedSomething = true;
 
     // Statistics.