[ARM][AArch64] BTI,GCS,PAC Module flag update. (#86212)

Module flag is used to indicate the feature to be propagated to the
function. As now the frontend emits all attributes accordingly let's
help the auto upgrade to only do work when old and new bitcodes are
merged.

Depends on #82819 and #86031

1 files changed, 13 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index e490b1c..3746bc04 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1325,22 +1325,29 @@ void CodeGenModule::Release() {
                               "tag-stack-memory-buildattr", 1);
 
   if (T.isARM() || T.isThumb() || T.isAArch64()) {
+    // Previously 1 is used and meant for the backed to derive the function
+    // attribute form it. 2 now means function attributes already set for all
+    // functions in this module, so no need to propagate those from the module
+    // flag. Value is only used in case of LTO module merge because the backend
+    // will see all required function attribute set already. Value is used
+    // before modules got merged. Any posive value means the feature is active
+    // and required binary markings need to be emit accordingly.
     if (LangOpts.BranchTargetEnforcement)
       getModule().addModuleFlag(llvm::Module::Min, "branch-target-enforcement",
-                                1);
+                                2);
     if (LangOpts.BranchProtectionPAuthLR)
       getModule().addModuleFlag(llvm::Module::Min, "branch-protection-pauth-lr",
-                                1);
+                                2);
     if (LangOpts.GuardedControlStack)
-      getModule().addModuleFlag(llvm::Module::Min, "guarded-control-stack", 1);
+      getModule().addModuleFlag(llvm::Module::Min, "guarded-control-stack", 2);
     if (LangOpts.hasSignReturnAddress())
-      getModule().addModuleFlag(llvm::Module::Min, "sign-return-address", 1);
+      getModule().addModuleFlag(llvm::Module::Min, "sign-return-address", 2);
     if (LangOpts.isSignReturnAddressScopeAll())
       getModule().addModuleFlag(llvm::Module::Min, "sign-return-address-all",
-                                1);
+                                2);
     if (!LangOpts.isSignReturnAddressWithAKey())
       getModule().addModuleFlag(llvm::Module::Min,
-                                "sign-return-address-with-bkey", 1);
+                                "sign-return-address-with-bkey", 2);
 
     if (LangOpts.PointerAuthELFGOT)
       getModule().addModuleFlag(llvm::Module::Min, "ptrauth-elf-got", 1);