[ObjC][ARC] Emit the retainRV marker as a module flag instead of named metadata.

[ahatanak]

Summary

https://reviews.llvm.org/D60302 made changes in the clang front-end so that the retainRV marker is emitted as a module flag. This patch implements the corresponding changes in the ARC contract pass and the auto-upgrader.

[steven_wu]

LGTM once the clang patch is good to land.

llvm/trunk/lib/IR/AutoUpgrade.cpp

if (Modified && Version != DEBUG_METADATA_VERSION) {
     DiagnosticInfoDebugMetadataVersion DiagVersion(M, Version);
     M.getContext().diagnose(DiagVersion);
   }
   return Modified;
 }
 
 bool llvm::UpgradeRetainReleaseMarker(Module &M) {
   bool Changed = false;
-  NamedMDNode *ModRetainReleaseMarker =
-      M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker");
+  const char *MarkerKey = "clang.arc.retainAutoreleasedReturnValueMarker";
+  NamedMDNode *ModRetainReleaseMarker = M.getNamedMetadata(MarkerKey);
   if (ModRetainReleaseMarker) {
     MDNode *Op = ModRetainReleaseMarker->getOperand(0);
     if (Op) {
       MDString *ID = dyn_cast_or_null<MDString>(Op->getOperand(0));
       if (ID) {
         SmallVector<StringRef, 4> ValueComp;
         ID->getString().split(ValueComp, "#");
         if (ValueComp.size() == 2) {
           std::string NewValue = ValueComp[0].str() + ";" + ValueComp[1].str();
-          Metadata *Ops[1] = {MDString::get(M.getContext(), NewValue)};
-          ModRetainReleaseMarker->setOperand(0,
-                                             MDNode::get(M.getContext(), Ops));
-          Changed = true;
+          ID = MDString::get(M.getContext(), NewValue);
         }
+        M.addModuleFlag(Module::Error, MarkerKey, ID);
+        M.eraseNamedMetadata(ModRetainReleaseMarker);
+        Changed = true;
       }
     }
   }
   return Changed;
 }
 
 bool llvm::UpgradeModuleFlags(Module &M) {
   NamedMDNode *ModFlags = M.getModuleFlagsMetadata();

llvm/trunk/lib/Transforms/ObjCARC/ObjCARCContract.cpp

bool ObjCARCContract::doInitialization(Module &M) {
   // If nothing in the Module uses ARC, don't do anything.
   Run = ModuleHasARC(M);
   if (!Run)
     return false;
 
   EP.init(&M);
 
   // Initialize RVInstMarker.
-  RVInstMarker = nullptr;
-  if (NamedMDNode *NMD =
-          M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
-    if (NMD->getNumOperands() == 1) {
-      const MDNode *N = NMD->getOperand(0);
-      if (N->getNumOperands() == 1)
-        if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
-          RVInstMarker = S;
-    }
+  const char *MarkerKey = "clang.arc.retainAutoreleasedReturnValueMarker";
+  RVInstMarker = dyn_cast_or_null<MDString>(M.getModuleFlag(MarkerKey));
 
   return false;
 }

llvm/trunk/test/Bitcode/upgrade-objcretainrelease.ll

 ; Test that comment token for objc retain release is upgraded from '#' to ';'
 ;
 ; RUN: llvm-dis < %s.bc | FileCheck %s
 
-; CHECK: "mov\09fp, fp\09\09; marker for objc_retainAutoreleaseReturnValue"
-
+; CHECK: !llvm.module.flags = !{!0}
+; CHECK: !0 = !{i32 1, !"clang.arc.retainAutoreleasedReturnValueMarker", !"mov\09fp, fp\09\09; marker for objc_retainAutoreleaseReturnValue"}

llvm/trunk/test/Transforms/ObjCARC/contract-marker-funclet.ll

 declare i8* @"\01?f@@YAPAUobjc_object@@XZ"()
 
 declare i32 @__CxxFrameHandler3(...)
 
 declare dllimport i8* @llvm.objc.retainAutoreleasedReturnValue(i8*)
 
 declare dllimport void @llvm.objc.release(i8*)
 
-!clang.arc.retainAutoreleasedReturnValueMarker = !{!0}
-!0 = !{!"movl\09%ebp, %ebp\09\09// marker for objc_retainAutoreleaseReturnValue"}
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"clang.arc.retainAutoreleasedReturnValueMarker", !"movl\09%ebp, %ebp\09\09// marker for objc_retainAutoreleaseReturnValue"}
 
 ; CHECK-LABEL: catch
 ; CHECK: call void asm sideeffect "movl{{.*}}%ebp, %ebp{{.*}}", ""() [ "funclet"(token %1) ]
 
 ; CHECK-LABEL: catch.1
 ; CHECK: call void asm sideeffect "movl{{.*}}%ebp, %ebp{{.*}}", ""() [ "funclet"(token %1) ]
 
 ; CHECK-LABEL: invoke.cont
 ; CHECK: call void asm sideeffect "movl{{.*}}%ebp, %ebp{{.*}}", ""(){{$}}

llvm/trunk/test/Transforms/ObjCARC/contract-marker.ll

 }
 
 
 declare i32* @qux()
 declare i8* @llvm.objc.retainAutoreleasedReturnValue(i8*)
 declare i8* @llvm.objc.unsafeClaimAutoreleasedReturnValue(i8*)
 declare void @bar(i8*)
 
-!clang.arc.retainAutoreleasedReturnValueMarker = !{!0}
+!llvm.module.flags = !{!0}
 
-!0 = !{!"mov\09r7, r7\09\09@ marker for return value optimization"}
+!0 = !{i32 1, !"clang.arc.retainAutoreleasedReturnValueMarker", !"mov\09r7, r7\09\09@ marker for return value optimization"}
 
 ; CHECK: attributes [[NUW]] = { nounwind }

llvm/trunk/test/Transforms/ObjCARC/contract-testcases.ll

invoke.cont:                                      ; preds = %entry
   unreachable
 
 lpad:                                             ; preds = %entry
   %tmp1 = landingpad { i8*, i32 }
           cleanup
   resume { i8*, i32 } undef
 }
 
-!clang.arc.retainAutoreleasedReturnValueMarker = !{!0}
+!llvm.module.flags = !{!0}
 
-!0 = !{!"mov\09r7, r7\09\09@ marker for objc_retainAutoreleaseReturnValue"}
+!0 = !{i32 1, !"clang.arc.retainAutoreleasedReturnValueMarker", !"mov\09r7, r7\09\09@ marker for objc_retainAutoreleaseReturnValue"}
 
 ; CHECK: attributes #0 = { optsize }
 ; CHECK: attributes [[NUW]] = { nounwind }