1 files changed, 29 insertions, 18 deletions

diff --git a/llvm/tools/llvm-reduce/deltas/ReduceInstructionsMIR.cpp b/llvm/tools/llvm-reduce/deltas/ReduceInstructionsMIR.cpp
index 3be2eae..f5486cf 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceInstructionsMIR.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceInstructionsMIR.cpp
@@ -45,6 +45,21 @@ static Register getPrevDefOfRCInMBB(MachineBasicBlock &MBB,
   return 0;
 }
 
+static bool shouldNotRemoveInstruction(const TargetInstrInfo &TII,
+                                       const MachineInstr &MI) {
+  if (MI.isTerminator())
+    return true;
+
+  // The MIR is almost certainly going to be invalid if frame instructions are
+  // deleted individually since they need to come in balanced pairs, so don't
+  // try to delete them.
+  if (MI.getOpcode() == TII.getCallFrameSetupOpcode() ||
+      MI.getOpcode() == TII.getCallFrameDestroyOpcode())
+    return true;
+
+  return false;
+}
+
 static void extractInstrFromFunction(Oracle &O, MachineFunction &MF) {
   MachineDominatorTree MDT;
   MDT.runOnMachineFunction(MF);
@@ -52,17 +67,17 @@ static void extractInstrFromFunction(Oracle &O, MachineFunction &MF) {
   auto MRI = &MF.getRegInfo();
   SetVector<MachineInstr *> ToDelete;
 
-  MachineInstr *TopMI = nullptr;
+  const TargetSubtargetInfo &STI = MF.getSubtarget();
+  const TargetInstrInfo *TII = STI.getInstrInfo();
+  MachineBasicBlock *EntryMBB = &*MF.begin();
+  MachineBasicBlock::iterator EntryInsPt =
+      EntryMBB->SkipPHIsLabelsAndDebug(EntryMBB->begin());
 
   // Mark MIs for deletion according to some criteria.
   for (auto &MBB : MF) {
     for (auto &MI : MBB) {
-      if (MI.isTerminator())
-        continue;
-      if (MBB.isEntryBlock() && !TopMI) {
-        TopMI = &MI;
+      if (shouldNotRemoveInstruction(*TII, MI))
         continue;
-      }
       if (!O.shouldKeep())
         ToDelete.insert(&MI);
     }
@@ -101,19 +116,15 @@ static void extractInstrFromFunction(Oracle &O, MachineFunction &MF) {
         }
       }
 
-      // If no dominating definition was found then add an implicit one to the
-      // first instruction in the entry block.
-
-      // FIXME: This should really insert IMPLICIT_DEF or G_IMPLICIT_DEF. We
-      // need to refine the reduction quality metric from number of serialized
-      // bytes to continue progressing if we're going to introduce new
-      // instructions.
-      if (!NewReg && TopMI) {
+      // If no dominating definition was found then add an implicit def to the
+      // top of the entry block.
+      if (!NewReg) {
         NewReg = MRI->cloneVirtualRegister(Reg);
-        TopMI->addOperand(MachineOperand::CreateReg(
-            NewReg, true /*IsDef*/, true /*IsImp*/, false /*IsKill*/,
-            MO.isDead(), MO.isUndef(), MO.isEarlyClobber(), MO.getSubReg(),
-            /*IsDebug*/ false, MO.isInternalRead()));
+        bool IsGeneric = MRI->getRegClassOrNull(Reg) == nullptr;
+        unsigned ImpDef = IsGeneric ? TargetOpcode::G_IMPLICIT_DEF
+                                    : TargetOpcode::IMPLICIT_DEF;
+        BuildMI(*EntryMBB, EntryInsPt, DebugLoc(), TII->get(ImpDef))
+          .addReg(NewReg, getRegState(MO), MO.getSubReg());
       }
 
       // Update all uses.