[AMDGPU][CodeGenModule] Change module flag behavior to override with …

…heterogeneous debug info

When linking modules with differing debug info versions this change sets the linked
module Debug Info version to v4 if at least one module has heterogeneous debug info.
This will ensure the heterogenous verify pass is run on the linked module.

Since modules with v3 will still have warning behavior set, the verifier will both
print a warning and update the module flag to v4 if we have mixed versions.

Change-Id: Ie116df03aa40bb2ba672b25ff1fd032d527faa1c

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1046,12 +1046,13 @@ void CodeGenModule::Release() {
     // We support a single version in the linked module. The LLVM
     // parser will drop debug info with a different version number
     // (and warn about it, too).
-    uint32_t DebugMetadataVersion =
-      CodeGenOpts.HeterogeneousDwarf ?
-        llvm::DEBUG_METADATA_VERSION_HETEROGENEOUS_DWARF :
-        llvm::DEBUG_METADATA_VERSION;
-    getModule().addModuleFlag(llvm::Module::Warning, "Debug Info Version",
-                              DebugMetadataVersion);
+    if (CodeGenOpts.HeterogeneousDwarf) {
+      getModule().addModuleFlag(llvm::Module::Override, "Debug Info Version",
+                                llvm::DEBUG_METADATA_VERSION_HETEROGENEOUS_DWARF);
+    } else {
+      getModule().addModuleFlag(llvm::Module::Warning, "Debug Info Version",
+                                llvm::DEBUG_METADATA_VERSION);
+    }
   }
 
   // We need to record the widths of enums and wchar_t, so that we can generate

clang/test/CodeGen/debug-info-version-heterogeneous-dwarf.c

@@ -4,5 +4,5 @@ int main (void) {
   return 0;
 }
 
-// CHECK:  i32 2, !"Debug Info Version", i32 4}
+// CHECK:  i32 4, !"Debug Info Version", i32 4}
 // NO_DEBUG-NOT: !"Debug Info Version"