[AArch64] Add isAuthenticated predicate to MCInstDesc

Add a predicate to MCInstDesc that allows tools to determine whether an
instruction authenticates a pointer. This can be used by diagnostic
tools to hint at pointer authentication failures.

Differential Revision: https://reviews.llvm.org/D70329

rdar://55089604

Author: vedantk

llvm/include/llvm/MC/MCInstrDesc.h

@@ -176,6 +176,7 @@ enum Flag {
   Add,
   Trap,
   VariadicOpsAreDefs,
+  Authenticated,
 };
 }
 
@@ -416,6 +417,15 @@ class MCInstrDesc {
     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 authenticated instruction may fail in an ABI-defined manner when
+  /// operating on an invalid signed pointer.
+  bool isAuthenticated() const {
+    return Flags & (1ULL << MCID::Authenticated);
+  }
+
   //===--------------------------------------------------------------------===//
   // Side Effect Analysis
   //===--------------------------------------------------------------------===//

llvm/include/llvm/Target/Target.td

@@ -530,6 +530,7 @@ class Instruction : InstructionEncoding {
   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 isAuthenticated = 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?

llvm/lib/Target/AArch64/AArch64InstrFormats.td

@@ -1483,6 +1483,7 @@ class RCPCLoad<bits<2> sz, string asm, RegisterClass RC>
 class AuthBase<bits<1> M, dag oops, dag iops, string asm, string operands,
                list<dag> pattern>
   : I<oops, iops, asm, operands, "", pattern>, Sched<[]> {
+  let isAuthenticated = 1;
   let Inst{31-25} = 0b1101011;
   let Inst{20-11} = 0b1111100001;
   let Inst{10} = M;
@@ -1522,6 +1523,7 @@ class BaseAuthLoad<bit M, bit W, dag oops, dag iops, string asm,
   bits<10> offset;
   bits<5> Rn;
   bits<5> Rt;
+  let isAuthenticated = 1;
   let Inst{31-24} = 0b11111000;
   let Inst{23} = M;
   let Inst{22} = offset{9};

llvm/lib/Target/AArch64/AArch64InstrInfo.td

@@ -819,20 +819,26 @@ let Predicates = [HasComplxNum, HasNEON] in {
 let Uses = [LR], Defs = [LR] in {
   def PACIAZ   : SystemNoOperands<0b000, "paciaz">;
   def PACIBZ   : SystemNoOperands<0b010, "pacibz">;
-  def AUTIAZ   : SystemNoOperands<0b100, "autiaz">;
-  def AUTIBZ   : SystemNoOperands<0b110, "autibz">;
+  let isAuthenticated = 1 in {
+    def AUTIAZ   : SystemNoOperands<0b100, "autiaz">;
+    def AUTIBZ   : SystemNoOperands<0b110, "autibz">;
+  }
 }
 let Uses = [LR, SP], Defs = [LR] in {
   def PACIASP  : SystemNoOperands<0b001, "paciasp">;
   def PACIBSP  : SystemNoOperands<0b011, "pacibsp">;
-  def AUTIASP  : SystemNoOperands<0b101, "autiasp">;
-  def AUTIBSP  : SystemNoOperands<0b111, "autibsp">;
+  let isAuthenticated = 1 in {
+    def AUTIASP  : SystemNoOperands<0b101, "autiasp">;
+    def AUTIBSP  : SystemNoOperands<0b111, "autibsp">;
+  }
 }
 let Uses = [X16, X17], Defs = [X17], CRm = 0b0001 in {
   def PACIA1716  : SystemNoOperands<0b000, "pacia1716">;
   def PACIB1716  : SystemNoOperands<0b010, "pacib1716">;
-  def AUTIA1716  : SystemNoOperands<0b100, "autia1716">;
-  def AUTIB1716  : SystemNoOperands<0b110, "autib1716">;
+  let isAuthenticated = 1 in {
+    def AUTIA1716  : SystemNoOperands<0b100, "autia1716">;
+    def AUTIB1716  : SystemNoOperands<0b110, "autib1716">;
+  }
 }
 
 let Uses = [LR], Defs = [LR], CRm = 0b0000 in {

llvm/unittests/Target/AArch64/InstSizes.cpp

@@ -78,6 +78,38 @@ void runChecks(
 
 } // 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().isAuthenticated());
+  };
+
+  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);
+
+  runChecks(TM.get(), II.get(), "",
+            "    \n"
+            "    frame-destroy AUTIASP implicit-def $lr, implicit killed $lr, implicit $sp\n",
+            isAuthInst);
+
+  runChecks(TM.get(), II.get(), "",
+            "    \n"
+            "    frame-destroy AUTIBSP implicit-def $lr, implicit killed $lr, implicit $sp\n",
+            isAuthInst);
+}
+
 TEST(InstSizes, STACKMAP) {
   std::unique_ptr<LLVMTargetMachine> TM = createTargetMachine();
   ASSERT_TRUE(TM);

llvm/utils/TableGen/CodeGenInstruction.cpp

@@ -396,6 +396,7 @@ CodeGenInstruction::CodeGenInstruction(Record *R)
   hasNoSchedulingInfo = R->getValueAsBit("hasNoSchedulingInfo");
   FastISelShouldIgnore = R->getValueAsBit("FastISelShouldIgnore");
   variadicOpsAreDefs = R->getValueAsBit("variadicOpsAreDefs");
+  isAuthenticated = R->getValueAsBit("isAuthenticated");
 
   bool Unset;
   mayLoad      = R->getValueAsBitOrUnset("mayLoad", Unset);

llvm/utils/TableGen/CodeGenInstruction.h

@@ -278,6 +278,7 @@ template <typename T> class ArrayRef;
     bool hasChain : 1;
     bool hasChain_Inferred : 1;
     bool variadicOpsAreDefs : 1;
+    bool isAuthenticated : 1;
 
     std::string DeprecatedReason;
     bool HasComplexDeprecationPredicate;

llvm/utils/TableGen/InstrDocsEmitter.cpp

@@ -138,6 +138,7 @@ void EmitInstrDocs(RecordKeeper &RK, raw_ostream &OS) {
     FLAG(isConvergent)
     FLAG(hasNoSchedulingInfo)
     FLAG(variadicOpsAreDefs)
+    FLAG(isAuthenticated)
     if (!FlagStrings.empty()) {
       OS << "Flags: ";
       bool IsFirst = true;

llvm/utils/TableGen/InstrInfoEmitter.cpp

@@ -708,6 +708,7 @@ void InstrInfoEmitter::emitRecord(const CodeGenInstruction &Inst, unsigned Num,
   if (Inst.isInsertSubreg) OS << "|(1ULL<<MCID::InsertSubreg)";
   if (Inst.isConvergent) OS << "|(1ULL<<MCID::Convergent)";
   if (Inst.variadicOpsAreDefs) OS << "|(1ULL<<MCID::VariadicOpsAreDefs)";
+  if (Inst.isAuthenticated) OS << "|(1ULL<<MCID::Authenticated)";
 
   // Emit all of the target-specific flags...
   BitsInit *TSF = Inst.TheDef->getValueAsBitsInit("TSFlags");