[llvm-branch-commits] Add llvm.protected.field.ptr intrinsic and pre-ISel lowering. (PR #151647)

[Nikita Popov via llvm-branch-commits]

================
@@ -461,6 +463,162 @@ bool PreISelIntrinsicLowering::expandMemIntrinsicUses(
   return Changed;
 }
 
+namespace {
+
+enum class PointerEncoding {
+  Rotate,
+  PACCopyable,
+  PACNonCopyable,
+};
+
+bool expandProtectedFieldPtr(Function &Intr) {
+  Module &M = *Intr.getParent();
+
+  SmallPtrSet<GlobalValue *, 2> DSsToDeactivate;
+  SmallPtrSet<Instruction *, 2> LoadsStores;
+
+  Type *Int8Ty = Type::getInt8Ty(M.getContext());
+  Type *Int64Ty = Type::getInt64Ty(M.getContext());
+  PointerType *PtrTy = PointerType::get(M.getContext(), 0);
+
+  Function *SignIntr =
+      Intrinsic::getOrInsertDeclaration(&M, Intrinsic::ptrauth_sign, {});
+  Function *AuthIntr =
+      Intrinsic::getOrInsertDeclaration(&M, Intrinsic::ptrauth_auth, {});
+
+  auto *EmuFnTy = FunctionType::get(Int64Ty, {Int64Ty, Int64Ty}, false);
+  FunctionCallee EmuSignIntr = M.getOrInsertFunction("__emupac_pacda", EmuFnTy);
+  FunctionCallee EmuAuthIntr = M.getOrInsertFunction("__emupac_autda", EmuFnTy);
+
+  auto CreateSign = [&](IRBuilder<> &B, Value *Val, Value *Disc,
+                       OperandBundleDef DSBundle) {
+    Function *F = B.GetInsertBlock()->getParent();
+    Attribute FSAttr = F->getFnAttribute("target-features");
+    if (FSAttr.isValid() && FSAttr.getValueAsString().contains("+pauth"))
+      return B.CreateCall(SignIntr, {Val, B.getInt32(2), Disc}, DSBundle);
+    return B.CreateCall(EmuSignIntr, {Val, Disc}, DSBundle);
+  };
+
+  auto CreateAuth = [&](IRBuilder<> &B, Value *Val, Value *Disc,
+                       OperandBundleDef DSBundle) {
+    Function *F = B.GetInsertBlock()->getParent();
+    Attribute FSAttr = F->getFnAttribute("target-features");
+    if (FSAttr.isValid() && FSAttr.getValueAsString().contains("+pauth"))
+      return B.CreateCall(AuthIntr, {Val, B.getInt32(2), Disc}, DSBundle);
+    return B.CreateCall(EmuAuthIntr, {Val, Disc}, DSBundle);
+  };
+
+  auto GetDeactivationSymbol = [&](CallInst *Call) -> GlobalValue * {
+    if (auto Bundle =
+            Call->getOperandBundle(LLVMContext::OB_deactivation_symbol))
+      return cast<GlobalValue>(Bundle->Inputs[0]);
+    return nullptr;
+  };
+
+  for (User *U : Intr.users()) {
+    auto *Call = cast<CallInst>(U);
+    auto *DS = GetDeactivationSymbol(Call);
+
+    for (Use &U : Call->uses()) {
+      if (auto *LI = dyn_cast<LoadInst>(U.getUser())) {
+        if (isa<PointerType>(LI->getType())) {
+          LoadsStores.insert(LI);
+          continue;
+        }
+      }
+      if (auto *SI = dyn_cast<StoreInst>(U.getUser())) {
+        if (U.getOperandNo() == 1 &&
+            isa<PointerType>(SI->getValueOperand()->getType())) {
+          LoadsStores.insert(SI);
+          continue;
+        }
+      }
+      // Comparisons against null cannot be used to recover the original
+      // pointer so we allow them.
+      if (auto *CI = dyn_cast<ICmpInst>(U.getUser())) {
+        if (auto *Op = dyn_cast<Constant>(CI->getOperand(0)))
+          if (Op->isNullValue())
+            continue;
+        if (auto *Op = dyn_cast<Constant>(CI->getOperand(1)))
+          if (Op->isNullValue())
+            continue;
+      }
+      if (DS)
+        DSsToDeactivate.insert(DS);
+    }
+  }
+
+  for (Instruction *I : LoadsStores) {
+    auto *PointerOperand = isa<StoreInst>(I)
+                               ? cast<StoreInst>(I)->getPointerOperand()
+                               : cast<LoadInst>(I)->getPointerOperand();
+    auto *Call = cast<CallInst>(PointerOperand);
+
+    auto *Disc = Call->getArgOperand(1);
+    bool UseHWEncoding = cast<ConstantInt>(Call->getArgOperand(2))->getZExtValue();
+
+    GlobalValue *DS = GetDeactivationSymbol(Call);
+    OperandBundleDef DSBundle("deactivation-symbol", DS);
+
+    if (auto *LI = dyn_cast<LoadInst>(I)) {
+      IRBuilder<> B(LI->getNextNode());
+      auto *LIInt = cast<Instruction>(B.CreatePtrToInt(LI, B.getInt64Ty()));
+      Value *Auth;
+      if (UseHWEncoding) {
+        Auth = CreateAuth(B, LIInt, Disc, DSBundle);
+      } else {
+        Auth = B.CreateAdd(LIInt, Disc);
+        Auth = B.CreateIntrinsic(
+            Auth->getType(), Intrinsic::fshr,
+            {Auth, Auth, ConstantInt::get(Auth->getType(), 16)});
+      }
+      LI->replaceAllUsesWith(B.CreateIntToPtr(Auth, B.getPtrTy()));
+      LIInt->setOperand(0, LI);
----------------
nikic wrote:

I found this code to be somewhat confusing. I think it would be more obvious to directly create a new load from the llvm.protected.field.ptr argument instead of rewriting things in this way and then later stripping out the intrinsic call.

https://github.com/llvm/llvm-project/pull/151647