[llvm-branch-commits] [MC][AArch64] Add .cfi_set_ra_state for PAuth_LR (PR #209949)

[Nathan Corbyn via llvm-branch-commits]

================
@@ -91,15 +133,37 @@ static void decoratePACWithCFI(MachineBasicBlock &MBB,
 
   auto &MF = *MBB.getParent();
   auto &MFnI = *MF.getInfo<AArch64FunctionInfo>();
-
   CFIInstBuilder CFIBuilder(MBB, MBBI, MachineInstr::FrameSetup);
+  const Triple &TT = MF.getTarget().getTargetTriple();
+
   if (MFnI.branchProtectionPAuthLR()) {
-    CFIBuilder.buildNegateRAStateWithPC();
-    BuildPACMI();
+    switch (CFILLVMSetRASignStateMode) {
+    case SetRAStateMode::Never:
+      CFIBuilder.buildNegateRAStateWithPC();
+      BuildPACMI();
+      break;
+    case SetRAStateMode::PAuthLR:
+    case SetRAStateMode::Always: {
+      BuildPACMI();
+      MCSymbol *PACSym = MFnI.getSigningInstrLabel();
+      assert(PACSym && "No PAC instruction to refer to");
+      CFIBuilder.buildSetRAState(2, PACSym);
+      break;
+    }
+    }
   } else {
-    BuildPACMI();
-    if (!MF.getTarget().getTargetTriple().isOSBinFormatMachO()) {
-      CFIBuilder.buildNegateRAState();
+    switch (CFILLVMSetRASignStateMode) {
+    case SetRAStateMode::Never:
+    case SetRAStateMode::PAuthLR:
+      BuildPACMI();
+      if (!TT.isOSBinFormatMachO()) {
+        CFIBuilder.buildNegateRAState();
+      }
+      break;
+    case SetRAStateMode::Always:
+      BuildPACMI();
+      CFIBuilder.buildSetRAState(1, nullptr);
+      break;
----------------
cofibrant wrote:

```suggestion
    BuildPACMI();
    switch (CFILLVMSetRASignStateMode) {
    case SetRAStateMode::Never:
    case SetRAStateMode::PAuthLR:
      if (!TT.isOSBinFormatMachO())
        CFIBuilder.buildNegateRAState();
      break;
    case SetRAStateMode::Always:
      CFIBuilder.buildSetRAState(1, nullptr);
      break;
```

https://github.com/llvm/llvm-project/pull/209949
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