[X86] Use Min behavior for cf-protection-{return,branch}/ibt-seal mod…

…ule flags

These features require that all object files are compiled with the support. When
the feature is disabled for an object file, the merge behavior should treat the
file having a value of 0 (see D129911).

Reviewed By: xiangzhangllvm

Differential Revision: https://reviews.llvm.org/D130065

clang/lib/CodeGen/CodeGenModule.cpp

@@ -743,19 +743,19 @@ void CodeGenModule::Release() {
   if (CodeGenOpts.CFProtectionReturn &&
       Target.checkCFProtectionReturnSupported(getDiags())) {
     // Indicate that we want to instrument return control flow protection.
-    getModule().addModuleFlag(llvm::Module::Override, "cf-protection-return",
+    getModule().addModuleFlag(llvm::Module::Min, "cf-protection-return",
                               1);
   }
 
   if (CodeGenOpts.CFProtectionBranch &&
       Target.checkCFProtectionBranchSupported(getDiags())) {
     // Indicate that we want to instrument branch control flow protection.
-    getModule().addModuleFlag(llvm::Module::Override, "cf-protection-branch",
+    getModule().addModuleFlag(llvm::Module::Min, "cf-protection-branch",
                               1);
   }
 
   if (CodeGenOpts.IBTSeal)
-    getModule().addModuleFlag(llvm::Module::Override, "ibt-seal", 1);
+    getModule().addModuleFlag(llvm::Module::Min, "ibt-seal", 1);
 
   if (CodeGenOpts.FunctionReturnThunks)
     getModule().addModuleFlag(llvm::Module::Override, "function_return_thunk_extern", 1);

clang/test/CodeGen/X86/x86-cf-protection.c

@@ -8,7 +8,7 @@
 // RETURN: #define __CET__ 2
 // BRANCH: #define __CET__ 1
 // FULL: #define __CET__ 3
-// CFPROT: "cf-protection-branch", i32 1
-// IBTSEAL: "ibt-seal", i32 1
+// CFPROT: !{i32 8, !"cf-protection-branch", i32 1}
+// IBTSEAL: !{i32 8, !"ibt-seal", i32 1}
 // NOIBTSEAL-NOT: "ibt-seal", i32 1
 void foo() {}