[AArch64][PAC][clang][ELF] Support PAuth ABI core info (#85235)

Depends on #87545

Emit PAuth ABI compatibility tag values as llvm module flags:
- `aarch64-elf-pauthabi-platform`
- `aarch64-elf-pauthabi-version`

For platform 0x10000002 (llvm_linux), the version value bits correspond
to the following LangOptions defined in #85232:

- bit 0: `PointerAuthIntrinsics`;
- bit 1: `PointerAuthCalls`;
- bit 2: `PointerAuthReturns`;
- bit 3: `PointerAuthAuthTraps`;
- bit 4: `PointerAuthVTPtrAddressDiscrimination`;
- bit 5: `PointerAuthVTPtrTypeDiscrimination`;
- bit 6: `PointerAuthInitFini`.

---------

Co-authored-by: Ahmed Bougacha <ahmed@bougacha.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index c8898ce..489c08a 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -53,6 +53,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Frontend/OpenMP/OMPIRBuilder.h"
 #include "llvm/IR/AttributeMask.h"
 #include "llvm/IR/CallingConv.h"
@@ -1190,6 +1191,37 @@ void CodeGenModule::Release() {
     if (!LangOpts.isSignReturnAddressWithAKey())
       getModule().addModuleFlag(llvm::Module::Min,
                                 "sign-return-address-with-bkey", 1);
+
+    if (getTriple().isOSLinux()) {
+      assert(getTriple().isOSBinFormatELF());
+      using namespace llvm::ELF;
+      uint64_t PAuthABIVersion =
+          (LangOpts.PointerAuthIntrinsics
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_INTRINSICS) |
+          (LangOpts.PointerAuthCalls
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_CALLS) |
+          (LangOpts.PointerAuthReturns
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_RETURNS) |
+          (LangOpts.PointerAuthAuthTraps
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_AUTHTRAPS) |
+          (LangOpts.PointerAuthVTPtrAddressDiscrimination
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_VPTRADDRDISCR) |
+          (LangOpts.PointerAuthVTPtrTypeDiscrimination
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_VPTRTYPEDISCR) |
+          (LangOpts.PointerAuthInitFini
+           << AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_INITFINI);
+      static_assert(AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_INITFINI ==
+                        AARCH64_PAUTH_PLATFORM_LLVM_LINUX_VERSION_LAST,
+                    "Update when new enum items are defined");
+      if (PAuthABIVersion != 0) {
+        getModule().addModuleFlag(llvm::Module::Error,
+                                  "aarch64-elf-pauthabi-platform",
+                                  AARCH64_PAUTH_PLATFORM_LLVM_LINUX);
+        getModule().addModuleFlag(llvm::Module::Error,
+                                  "aarch64-elf-pauthabi-version",
+                                  PAuthABIVersion);
+      }
+    }
   }
 
   if (CodeGenOpts.StackClashProtector)