diff --git a/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def b/llvm/include/llvm/Frontend/OpenMP/OMPKinds.defindex f974cfc78c8dd..e01f30912f891 100644--- a/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def+++ b/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def@@ -1418,3 +1418,26 @@ __OMP_ASSUME_CLAUSE(llvm::StringLiteral("no_parallelism"), false, false, false) #undef __OMP_ASSUME_CLAUSE #undef OMP_ASSUME_CLAUSE ///}+++/// Callback specification+///+///{++#ifndef OMP_CALLBACK+#define OMP_CALLBACK(Enum, VarArgsArePassed, CallbackArgNo, ...)+#endif++#define __OMP_CALLBACK(Name, VarArgsArePassed, CallbackArgNo, ...)             \+  OMP_CALLBACK(OMPRTL_##Name, VarArgsArePassed, CallbackArgNo, __VA_ARGS__)++__OMP_CALLBACK(__kmpc_fork_call, true, 2, -1, -1)+__OMP_CALLBACK(__kmpc_fork_call_if, true, 2, -1, -1)+__OMP_CALLBACK(__kmpc_fork_teams, true, 2, -1, -1)+__OMP_CALLBACK(__kmpc_omp_task_alloc, true, 5, -1, -1)++#undef __OMP_PTR_TYPE++#undef __OMP_TYPE+#undef OMP_CALLBACK+///}diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cppindex ca3d8438654dc..ac42cd9ab3297 100644--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp@@ -614,21 +614,27 @@ OpenMPIRBuilder::getOrCreateRuntimeFunction(Module &M, RuntimeFunction FnID) { #include "llvm/Frontend/OpenMP/OMPKinds.def"     }-    // Add information if the runtime function takes a callback function-    if (FnID == OMPRTL___kmpc_fork_call || FnID == OMPRTL___kmpc_fork_teams) {-      if (!Fn->hasMetadata(LLVMContext::MD_callback)) {-        LLVMContext &Ctx = Fn->getContext();-        MDBuilder MDB(Ctx);-        // Annotate the callback behavior of the runtime function:-        //  - The callback callee is argument number 2 (microtask).-        //  - The first two arguments of the callback callee are unknown (-1).-        //  - All variadic arguments to the runtime function are passed to the-        //    callback callee.-        Fn->addMetadata(-            LLVMContext::MD_callback,-            *MDNode::get(Ctx, {MDB.createCallbackEncoding(-                                  2, {-1, -1}, /* VarArgsArePassed */ true)}));-      }+    // Annotate the callback behavior of the runtime function:+    //  - First the callback callee argument number+    //  - Then the arguments passed on to the callback (-1 for unknown),+    //    variadic+    //  - Finally, whether variadic args are passed on to the callback.+    LLVMContext &Ctx = Fn->getContext();+    MDBuilder MDB(Ctx);+    switch (FnID) {+#define OMP_CALLBACK(Enum, VarArgsArePassed, CallbackArgNo, ...)               \+  case Enum: {                                                                 \+    if (!Fn->hasMetadata(LLVMContext::MD_callback)) {                          \+      Fn->addMetadata(LLVMContext::MD_callback,                                \+                      *MDNode::get(Ctx, {MDB.createCallbackEncoding(           \+                                            CallbackArgNo, {__VA_ARGS__},      \+                                            VarArgsArePassed)}));              \+    }                                                                          \+    break;                                                                     \+  }+#include "llvm/Frontend/OpenMP/OMPKinds.def"+    default:+      break;     }      LLVM_DEBUG(dbgs() << "Created OpenMP runtime function " << Fn->getName()diff --git a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cppindex be98be260c9dc..6cb7b8664c64f 100644--- a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp+++ b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp@@ -7702,4 +7702,55 @@ TEST_F(OpenMPIRBuilderTest, splitBB) {     EXPECT_TRUE(DL == AllocaBB->getTerminator()->getStableDebugLoc()); }+TEST_F(OpenMPIRBuilderTest, createCallbackMetadata) {+  OpenMPIRBuilder OMPBuilder(*M);+  OMPBuilder.initialize();++  FunctionCallee ForkCall = OMPBuilder.getOrCreateRuntimeFunction(+      *M, llvm::omp::RuntimeFunction::OMPRTL___kmpc_fork_call);+  FunctionCallee ForkCallIf = OMPBuilder.getOrCreateRuntimeFunction(+      *M, llvm::omp::RuntimeFunction::OMPRTL___kmpc_fork_call_if);+  FunctionCallee ForkTeam = OMPBuilder.getOrCreateRuntimeFunction(+      *M, llvm::omp::RuntimeFunction::OMPRTL___kmpc_fork_teams);+  FunctionCallee TaskAlloc = OMPBuilder.getOrCreateRuntimeFunction(+      *M, llvm::omp::RuntimeFunction::OMPRTL___kmpc_omp_task_alloc);++  M->dump();+  for (auto [FC, ArgNo] : zip(SmallVector<FunctionCallee>(+                                  {ForkCall, ForkCallIf, ForkTeam, TaskAlloc}),+                              SmallVector<unsigned>({2, 2, 2, 5}))) {+    MDNode *CallbackMD =+        cast<Function>(FC.getCallee())->getMetadata(LLVMContext::MD_callback);+    EXPECT_NE(CallbackMD, nullptr);+    unsigned Num = 0;+    CallbackMD->dump();+    M->dump();+    for (const MDOperand &Op : CallbackMD->operands()) {+      Num++;+      MDNode *OpMD = cast<MDNode>(Op.get());+      auto *CBCalleeIdxAsCM = cast<ConstantAsMetadata>(OpMD->getOperand(0));+      uint64_t CBCalleeIdx =+          cast<ConstantInt>(CBCalleeIdxAsCM->getValue())->getZExtValue();+      EXPECT_EQ(CBCalleeIdx, ArgNo);++      uint64_t Arg0 =+          cast<ConstantInt>(+              cast<ConstantAsMetadata>(OpMD->getOperand(1))->getValue())+              ->getZExtValue();+      uint64_t Arg1 =+          cast<ConstantInt>(+              cast<ConstantAsMetadata>(OpMD->getOperand(2))->getValue())+              ->getZExtValue();+      uint64_t VarArg =+          cast<ConstantInt>(+              cast<ConstantAsMetadata>(OpMD->getOperand(3))->getValue())+              ->getZExtValue();+      EXPECT_EQ(Arg0, -1);+      EXPECT_EQ(Arg1, -1);+      EXPECT_EQ(VarArg, true);+    }+    EXPECT_EQ(Num, 1);+  }+}+ } // namespace