Index: llvm/include/llvm/MC/MCInstrDesc.h
===================================================================
--- llvm/include/llvm/MC/MCInstrDesc.h
+++ llvm/include/llvm/MC/MCInstrDesc.h
@@ -168,6 +168,7 @@
   Add,
   Trap,
   VariadicOpsAreDefs,
+  Authenticating,
 };
 }
 
@@ -408,6 +409,15 @@
     return Flags & (1ULL << MCID::VariadicOpsAreDefs);
   }
 
+  /// Return true if this instruction authenticates a pointer (e.g. LDRAx/BRAx
+  /// from ARMv8.3, which perform loads/branches with authentication).
+  ///
+  /// An authenticating instructions may fail in an ABI-defined manner when
+  /// operating on an invalid signed pointer.
+  bool isAuthenticating() const {
+    return Flags & (1ULL << MCID::Authenticating);
+  }
+
   //===--------------------------------------------------------------------===//
   // Side Effect Analysis
   //===--------------------------------------------------------------------===//
Index: llvm/include/llvm/Target/Target.td
===================================================================
--- llvm/include/llvm/Target/Target.td
+++ llvm/include/llvm/Target/Target.td
@@ -530,6 +530,7 @@
   bit hasCtrlDep   = 0;     // Does this instruction r/w ctrl-flow chains?
   bit isNotDuplicable = 0;  // Is it unsafe to duplicate this instruction?
   bit isConvergent = 0;     // Is this instruction convergent?
+  bit isAuthenticating = 0;  // Does this instruction authenticate a pointer?
   bit isAsCheapAsAMove = 0; // As cheap (or cheaper) than a move instruction.
   bit hasExtraSrcRegAllocReq = 0; // Sources have special regalloc requirement?
   bit hasExtraDefRegAllocReq = 0; // Defs have special regalloc requirement?
Index: llvm/lib/Target/AArch64/AArch64InstrFormats.td
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1410,6 +1410,7 @@
 class AuthBase<bits<1> M, dag oops, dag iops, string asm, string operands,
                list<dag> pattern>
   : I<oops, iops, asm, operands, "", pattern>, Sched<[]> {
+  let isAuthenticating = 1;
   let Inst{31-25} = 0b1101011;
   let Inst{20-11} = 0b1111100001;
   let Inst{10} = M;
@@ -1449,6 +1450,7 @@
   bits<10> offset;
   bits<5> Rn;
   bits<5> Rt;
+  let isAuthenticating = 1;
   let Inst{31-24} = 0b11111000;
   let Inst{23} = M;
   let Inst{22} = offset{9};
Index: llvm/unittests/Target/AArch64/InstSizes.cpp
===================================================================
--- llvm/unittests/Target/AArch64/InstSizes.cpp
+++ llvm/unittests/Target/AArch64/InstSizes.cpp
@@ -78,6 +78,28 @@
 
 } // anonymous namespace
 
+TEST(InstSizes, Authenticated) {
+  std::unique_ptr<LLVMTargetMachine> TM = createTargetMachine();
+  ASSERT_TRUE(TM);
+  std::unique_ptr<AArch64InstrInfo> II = createInstrInfo(TM.get());
+
+  auto isAuthInst = [](AArch64InstrInfo &II, MachineFunction &MF) {
+    auto I = MF.begin()->begin();
+    EXPECT_EQ(4u, II.getInstSizeInBytes(*I));
+    EXPECT_TRUE(I->getDesc().isAuthenticating());
+  };
+
+  runChecks(TM.get(), II.get(), "",
+            "    \n"
+            "    BLRAA $x10, $x9\n",
+            isAuthInst);
+
+  runChecks(TM.get(), II.get(), "",
+            "    \n"
+            "    RETAB implicit $lr, implicit $sp, implicit killed $x0\n",
+            isAuthInst);
+}
+
 TEST(InstSizes, STACKMAP) {
   std::unique_ptr<LLVMTargetMachine> TM = createTargetMachine();
   ASSERT_TRUE(TM);
Index: llvm/utils/TableGen/CodeGenInstruction.h
===================================================================
--- llvm/utils/TableGen/CodeGenInstruction.h
+++ llvm/utils/TableGen/CodeGenInstruction.h
@@ -278,6 +278,7 @@
     bool hasChain : 1;
     bool hasChain_Inferred : 1;
     bool variadicOpsAreDefs : 1;
+    bool isAuthenticating : 1;
 
     std::string DeprecatedReason;
     bool HasComplexDeprecationPredicate;
Index: llvm/utils/TableGen/CodeGenInstruction.cpp
===================================================================
--- llvm/utils/TableGen/CodeGenInstruction.cpp
+++ llvm/utils/TableGen/CodeGenInstruction.cpp
@@ -396,6 +396,7 @@
   hasNoSchedulingInfo = R->getValueAsBit("hasNoSchedulingInfo");
   FastISelShouldIgnore = R->getValueAsBit("FastISelShouldIgnore");
   variadicOpsAreDefs = R->getValueAsBit("variadicOpsAreDefs");
+  isAuthenticating = R->getValueAsBit("isAuthenticating");
 
   bool Unset;
   mayLoad      = R->getValueAsBitOrUnset("mayLoad", Unset);
Index: llvm/utils/TableGen/InstrDocsEmitter.cpp
===================================================================
--- llvm/utils/TableGen/InstrDocsEmitter.cpp
+++ llvm/utils/TableGen/InstrDocsEmitter.cpp
@@ -138,6 +138,7 @@
     FLAG(isConvergent)
     FLAG(hasNoSchedulingInfo)
     FLAG(variadicOpsAreDefs)
+    FLAG(isAuthenticating)
     if (!FlagStrings.empty()) {
       OS << "Flags: ";
       bool IsFirst = true;
Index: llvm/utils/TableGen/InstrInfoEmitter.cpp
===================================================================
--- llvm/utils/TableGen/InstrInfoEmitter.cpp
+++ llvm/utils/TableGen/InstrInfoEmitter.cpp
@@ -703,6 +703,7 @@
   if (Inst.isInsertSubreg) OS << "|(1ULL<<MCID::InsertSubreg)";
   if (Inst.isConvergent) OS << "|(1ULL<<MCID::Convergent)";
   if (Inst.variadicOpsAreDefs) OS << "|(1ULL<<MCID::VariadicOpsAreDefs)";
+  if (Inst.isAuthenticating) OS << "|(1ULL<<MCID::Authenticating)";
 
   // Emit all of the target-specific flags...
   BitsInit *TSF = Inst.TheDef->getValueAsBitsInit("TSFlags");