[llvm-branch-commits] [llvm] [AArch64][PAC] Lower authenticated calls with ptrauth bundles. (PR #85736)

[Daniil Kovalev via llvm-branch-commits]

================
@@ -1909,9 +1948,60 @@ void AArch64AsmPrinter::emitInstruction(const 
MachineInstr *MI) {
     emitPtrauthAuthResign(MI);
     return;
 
+  case AArch64::BLRA:
+    emitPtrauthBranch(MI);
+    return;
+
   // Tail calls use pseudo instructions so they have the proper code-gen
   // attributes (isCall, isReturn, etc.). We lower them to the real
   // instruction here.
+  case AArch64::AUTH_TCRETURN:
+  case AArch64::AUTH_TCRETURN_BTI: {
+    const uint64_t Key = MI->getOperand(2).getImm();
+    assert(Key < 2 && "Unknown key kind for authenticating tail-call return");
+    const uint64_t Disc = MI->getOperand(3).getImm();
+    Register AddrDisc = MI->getOperand(4).getReg();
+
+    Register ScratchReg = MI->getOperand(0).getReg() == AArch64::X16
+                              ? AArch64::X17
+                              : AArch64::X16;
+
+    unsigned DiscReg = AddrDisc;
+    if (Disc) {
+      assert(isUInt<16>(Disc) && "Integer discriminator is too wide");
+
+      if (AddrDisc != AArch64::NoRegister) {
+        EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::ORRXrs)
+                                         .addReg(ScratchReg)
+                                         .addReg(AArch64::XZR)
+                                         .addReg(AddrDisc)
+                                         .addImm(0));
+        EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::MOVKXi)
+                                         .addReg(ScratchReg)
+                                         .addReg(ScratchReg)
+                                         .addImm(Disc)
+                                         .addImm(/*shift=*/48));
+      } else {
+        EmitToStreamer(*OutStreamer, MCInstBuilder(AArch64::MOVZXi)
+                                         .addReg(ScratchReg)
+                                         .addImm(Disc)
+                                         .addImm(/*shift=*/0));
+      }
+      DiscReg = ScratchReg;
+    }
+
+    const bool isZero = DiscReg == AArch64::NoRegister;
----------------
kovdan01 wrote:

```suggestion
    const bool IsZero = DiscReg == AArch64::NoRegister;
```

https://github.com/llvm/llvm-project/pull/85736
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