[ObjC] Support objc_claimAutoreleasedReturnValue.

This adds basic support for objc_claimAutoreleasedReturnValue, which is mostly equivalent to objc_retainAutoreleasedReturnValue, with the difference that it doesn't require the marker nop to be emitted between it and the call it was attached to. To achieve that, this also teaches the AArch64 attachedcall bundle lowering to pick whether the marker should be emitted or not based on whether the attachedcall target is claimARV or retainARV. Co-authored-by: Ahmed Bougacha <ahmed@bougacha.org>
llvm · citymarina · May 13, 2025 · Mar 19, 2025 · May 12, 2025 · e83258e216f89992a7c46eaf3478c7b31e1113dc
commit e83258e216f89992a7c46eaf3478c7b31e1113dc
diff --git a/llvm/include/llvm/Analysis/ObjCARCUtil.h b/llvm/include/llvm/Analysis/ObjCARCUtil.h
@@ -48,6 +48,21 @@ inline std::optional<Function *> getAttachedARCFunction(const CallBase *CB) {
  return cast<Function>(B->Inputs[0]);
 }

+/// This function determines whether the clang_arc_attachedcall should be
+/// emitted with or without the marker.
+/// Concretely, this is the difference between:
+///   objc_retainAutoreleasedReturnValue
+/// and
+///  objc_claimAutoreleasedReturnValue
+/// retainRV (and unsafeClaimRV) requires a marker, but claimRV does not.
+inline bool attachedCallOpBundleNeedsMarker(const CallBase *CB) {
+  // FIXME: do this on ARCRuntimeEntryPoints, and do the todo above ARCInstKind
+  if (std::optional<Function *> Fn = getAttachedARCFunction(CB))
+    if ((*Fn)->getName() == "objc_claimAutoreleasedReturnValue")
+      return false;
+  return true;
+}
+
 /// Check whether the function is retainRV/unsafeClaimRV.
 inline bool isRetainOrClaimRV(ARCInstKind Kind) {
  return Kind == ARCInstKind::RetainRV || Kind == ARCInstKind::UnsafeClaimRV;

diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
@@ -777,10 +777,12 @@ def int_objc_loadWeakRetained               : Intrinsic<[llvm_ptr_ty],
 def int_objc_moveWeak                       : Intrinsic<[],
                                                        [llvm_ptr_ty,
                                                         llvm_ptr_ty]>;
+
 def int_objc_release                        : Intrinsic<[], [llvm_ptr_ty]>;
 def int_objc_retain                         : Intrinsic<[llvm_ptr_ty],
                                                        [llvm_ptr_ty],
                                                        [Returned<ArgIndex<0>>]>;
+
 def int_objc_retainAutorelease              : Intrinsic<[llvm_ptr_ty],
                                                        [llvm_ptr_ty],
                                                        [Returned<ArgIndex<0>>]>;
@@ -789,6 +791,11 @@ def int_objc_retainAutoreleaseReturnValue   : Intrinsic<[llvm_ptr_ty],
                                                        [Returned<ArgIndex<0>>]>;
 def int_objc_retainAutoreleasedReturnValue  : Intrinsic<[llvm_ptr_ty],
                                                        [llvm_ptr_ty]>;
+def int_objc_unsafeClaimAutoreleasedReturnValue : Intrinsic<[llvm_ptr_ty],
+                                                            [llvm_ptr_ty]>;
+def int_objc_claimAutoreleasedReturnValue   : Intrinsic<[llvm_ptr_ty],
+                                                        [llvm_ptr_ty]>;
+
 def int_objc_retainBlock                    : Intrinsic<[llvm_ptr_ty],
                                                        [llvm_ptr_ty]>;
 def int_objc_storeStrong                    : Intrinsic<[],
@@ -802,8 +809,6 @@ def int_objc_clang_arc_use                  : Intrinsic<[],
 def int_objc_clang_arc_noop_use : DefaultAttrsIntrinsic<[],
                                                        [llvm_vararg_ty],
                                                        [IntrInaccessibleMemOnly]>;
-def int_objc_unsafeClaimAutoreleasedReturnValue : Intrinsic<[llvm_ptr_ty],
-                                                            [llvm_ptr_ty]>;
 def int_objc_retainedObject                 : Intrinsic<[llvm_ptr_ty],
                                                        [llvm_ptr_ty]>;
 def int_objc_unretainedObject               : Intrinsic<[llvm_ptr_ty],

diff --git a/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp b/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp
@@ -160,10 +160,7 @@ static bool lowerObjCCall(Function &F, const char *NewFn,
    auto *CB = cast<CallBase>(U.getUser());

    if (CB->getCalledFunction() != &F) {
-      objcarc::ARCInstKind Kind = objcarc::getAttachedARCFunctionKind(CB);
-      (void)Kind;
-      assert((Kind == objcarc::ARCInstKind::RetainRV ||
-              Kind == objcarc::ARCInstKind::UnsafeClaimRV) &&
+      assert(objcarc::getAttachedARCFunction(CB) == &F &&
             "use expected to be the argument of operand bundle "
             "\"clang.arc.attachedcall\"");
      U.set(FCache.getCallee());
@@ -529,6 +526,9 @@ bool PreISelIntrinsicLowering::lowerIntrinsics(Module &M) const {
    case Intrinsic::objc_retainAutoreleasedReturnValue:
      Changed |= lowerObjCCall(F, "objc_retainAutoreleasedReturnValue");
      break;
+    case Intrinsic::objc_claimAutoreleasedReturnValue:
+      Changed |= lowerObjCCall(F, "objc_claimAutoreleasedReturnValue");
+      break;
    case Intrinsic::objc_retainBlock:
      Changed |= lowerObjCCall(F, "objc_retainBlock");
      break;

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
@@ -7282,11 +7282,13 @@ void Verifier::verifyAttachedCallBundle(const CallBase &Call,

  if (IID) {
    Check((IID == Intrinsic::objc_retainAutoreleasedReturnValue ||
+           IID == Intrinsic::objc_claimAutoreleasedReturnValue ||
           IID == Intrinsic::objc_unsafeClaimAutoreleasedReturnValue),
          "invalid function argument", Call);
  } else {
    StringRef FnName = Fn->getName();
    Check((FnName == "objc_retainAutoreleasedReturnValue" ||
+           FnName == "objc_claimAutoreleasedReturnValue" ||
           FnName == "objc_unsafeClaimAutoreleasedReturnValue"),
          "invalid function argument", Call);
  }

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -9542,10 +9542,10 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
    Ops.insert(Ops.begin() + 1, GA);

    // We may or may not need to emit both the marker and the retain/claim call.
-    // Do what the frontend tells us: if the rvmarker module flag is present,
-    // emit the marker.  Always emit the call regardless.
    // Tell the pseudo expansion using an additional boolean op.
-    SDValue DoEmitMarker = DAG.getTargetConstant(true, DL, MVT::i32);
+    bool ShouldEmitMarker = objcarc::attachedCallOpBundleNeedsMarker(CLI.CB);
+    SDValue DoEmitMarker =
+        DAG.getTargetConstant(ShouldEmitMarker, DL, MVT::i32);
    Ops.insert(Ops.begin() + 2, DoEmitMarker);
  } else if (CallConv == CallingConv::ARM64EC_Thunk_X64) {
    Opc = AArch64ISD::CALL_ARM64EC_TO_X64;

diff --git a/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp b/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
@@ -1366,10 +1366,8 @@ bool AArch64CallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
    ++CalleeOpNo;

    // We may or may not need to emit both the marker and the retain/claim call.
-    // Do what the frontend tells us: if the rvmarker module flag is present,
-    // emit the marker.  Always emit the call regardless.
    // Tell the pseudo expansion using an additional boolean op.
-    MIB.addImm(true);
+    MIB.addImm(objcarc::attachedCallOpBundleNeedsMarker(Info.CB));
    ++CalleeOpNo;
  } else if (Info.CFIType) {
    MIB->setCFIType(MF, Info.CFIType->getZExtValue());

diff --git a/llvm/test/CodeGen/AArch64/call-rv-marker.ll b/llvm/test/CodeGen/AArch64/call-rv-marker.ll
@@ -544,7 +544,35 @@ define dso_local void @rv_marker_multiarg(i64 %a, i64 %b, i64 %c) {
  ret void
 }

+define dso_local ptr @rv_marker_claim() {
+; SELDAG-LABEL: rv_marker_claim:
+; SELDAG:       ; %bb.0: ; %entry
+; SELDAG-NEXT:    stp x29, x30, [sp, #-16]! ; 16-byte Folded Spill
+; SELDAG-NEXT:    .cfi_def_cfa_offset 16
+; SELDAG-NEXT:    .cfi_offset w30, -8
+; SELDAG-NEXT:    .cfi_offset w29, -16
+; SELDAG-NEXT:    bl _foo1
+; SELDAG-NEXT:    bl _objc_claimAutoreleasedReturnValue
+; SELDAG-NEXT:    ldp x29, x30, [sp], #16 ; 16-byte Folded Reload
+; SELDAG-NEXT:    ret
+;
+; GISEL-LABEL: rv_marker_claim:
+; GISEL:       ; %bb.0: ; %entry
+; GISEL-NEXT:    stp x29, x30, [sp, #-16]! ; 16-byte Folded Spill
+; GISEL-NEXT:    .cfi_def_cfa_offset 16
+; GISEL-NEXT:    .cfi_offset w30, -8
+; GISEL-NEXT:    .cfi_offset w29, -16
+; GISEL-NEXT:    bl _foo1
+; GISEL-NEXT:    bl _objc_claimAutoreleasedReturnValue
+; GISEL-NEXT:    ldp x29, x30, [sp], #16 ; 16-byte Folded Reload
+; GISEL-NEXT:    ret
+entry:
+  %call = call ptr @foo1() [ "clang.arc.attachedcall"(ptr @objc_claimAutoreleasedReturnValue) ]
+  ret ptr %call
+}
+
 declare ptr @objc_retainAutoreleasedReturnValue(ptr)
+declare ptr @objc_claimAutoreleasedReturnValue(ptr)
 declare ptr @objc_unsafeClaimAutoreleasedReturnValue(ptr)
 declare i32 @__gxx_personality_v0(...)
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line: