1 files changed, 24 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 5d3c2999a11..759a8d3234d 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -117,7 +117,7 @@ public:
   void printOffset(int64_t Offset);
   void printTargetFlags(const MachineOperand &Op);
   void print(const MachineOperand &Op, const TargetRegisterInfo *TRI,
-             bool IsDef = false);
+             unsigned I, bool ShouldPrintRegisterTies, bool IsDef = false);
   void print(const MachineMemOperand &Op);
 
   void print(const MCCFIInstruction &CFI, const TargetRegisterInfo *TRI);
@@ -502,6 +502,23 @@ void MIPrinter::print(const MachineBasicBlock &MBB) {
     OS.indent(2) << "}\n";
 }
 
+/// Return true when an instruction has tied register that can't be determined
+/// by the instruction's descriptor.
+static bool hasComplexRegisterTies(const MachineInstr &MI) {
+  const MCInstrDesc &MCID = MI.getDesc();
+  for (unsigned I = 0, E = MI.getNumOperands(); I < E; ++I) {
+    const auto &Operand = MI.getOperand(I);
+    if (!Operand.isReg() || Operand.isDef())
+      // Ignore the defined registers as MCID marks only the uses as tied.
+      continue;
+    int ExpectedTiedIdx = MCID.getOperandConstraint(I, MCOI::TIED_TO);
+    int TiedIdx = Operand.isTied() ? int(MI.findTiedOperandIdx(I)) : -1;
+    if (ExpectedTiedIdx != TiedIdx)
+      return true;
+  }
+  return false;
+}
+
 void MIPrinter::print(const MachineInstr &MI) {
   const auto &SubTarget = MI.getParent()->getParent()->getSubtarget();
   const auto *TRI = SubTarget.getRegisterInfo();
@@ -511,13 +528,14 @@ void MIPrinter::print(const MachineInstr &MI) {
   if (MI.isCFIInstruction())
     assert(MI.getNumOperands() == 1 && "Expected 1 operand in CFI instruction");
 
+  bool ShouldPrintRegisterTies = hasComplexRegisterTies(MI);
   unsigned I = 0, E = MI.getNumOperands();
   for (; I < E && MI.getOperand(I).isReg() && MI.getOperand(I).isDef() &&
          !MI.getOperand(I).isImplicit();
        ++I) {
     if (I)
       OS << ", ";
-    print(MI.getOperand(I), TRI, /*IsDef=*/true);
+    print(MI.getOperand(I), TRI, I, ShouldPrintRegisterTies, /*IsDef=*/true);
   }
 
   if (I)
@@ -532,7 +550,7 @@ void MIPrinter::print(const MachineInstr &MI) {
   for (; I < E; ++I) {
     if (NeedComma)
       OS << ", ";
-    print(MI.getOperand(I), TRI);
+    print(MI.getOperand(I), TRI, I, ShouldPrintRegisterTies);
     NeedComma = true;
   }
 
@@ -690,11 +708,10 @@ static const char *getTargetIndexName(const MachineFunction &MF, int Index) {
 }
 
 void MIPrinter::print(const MachineOperand &Op, const TargetRegisterInfo *TRI,
-                      bool IsDef) {
+                      unsigned I, bool ShouldPrintRegisterTies, bool IsDef) {
   printTargetFlags(Op);
   switch (Op.getType()) {
   case MachineOperand::MO_Register:
-    // FIXME: Serialize the tied register.
     if (Op.isImplicit())
       OS << (Op.isDef() ? "implicit-def " : "implicit ");
     else if (!IsDef && Op.isDef())
@@ -716,6 +733,8 @@ void MIPrinter::print(const MachineOperand &Op, const TargetRegisterInfo *TRI,
     // Print the sub register.
     if (Op.getSubReg() != 0)
       OS << ':' << TRI->getSubRegIndexName(Op.getSubReg());
+    if (ShouldPrintRegisterTies && Op.isTied() && !Op.isDef())
+      OS << "(tied-def " << Op.getParent()->findTiedOperandIdx(I) << ")";
     break;
   case MachineOperand::MO_Immediate:
     OS << Op.getImm();