[llvm] [AArch64][PAC][MC][ELF] Support PAuth ABI compatibility tag (PR #85236)

[Daniel Kiss via llvm-commits]

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@@ -268,13 +268,24 @@ void AArch64AsmPrinter::emitStartOfAsmFile(Module &M) {
     if (Sign->getZExtValue())
       Flags |= ELF::GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
 
-  if (Flags == 0)
-    return;
+  uint64_t PAuthABIPlatform = -1;
+  if (const auto *PAP = mdconst::extract_or_null<ConstantInt>(
+          M.getModuleFlag("aarch64-elf-pauthabi-platform")))
+    PAuthABIPlatform = PAP->getZExtValue();
+  uint64_t PAuthABIVersion = -1;
+  if (const auto *PAV = mdconst::extract_or_null<ConstantInt>(
+          M.getModuleFlag("aarch64-elf-pauthabi-version")))
+    PAuthABIVersion = PAV->getZExtValue();
+
+  if ((PAuthABIPlatform == uint64_t(-1)) != (PAuthABIVersion == uint64_t(-1)))
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DanielKristofKiss wrote:

could this check be added to the verifier?

https://github.com/llvm/llvm-project/pull/85236