[Mlir-commits] [mlir] [flang][mlir] Add support for translating task_reduction to LLVMIR (PR #120957)

[Kareem Ergawy]

================
@@ -1787,16 +1779,264 @@ convertOmpTaskOp(omp::TaskOp taskOp, llvm::IRBuilderBase &builder,
   return success();
 }
 
+template <typename OP>
+llvm::Value *createTaskReductionFunction(
+    llvm::IRBuilderBase &builder, const std::string &name, llvm::Type *redTy,
+    LLVM::ModuleTranslation &moduleTranslation,
+    SmallVectorImpl<omp::DeclareReductionOp> &reductionDecls, Region &region,
+    OP &op, unsigned Cnt, llvm::ArrayRef<bool> &isByRef,
+    SmallVectorImpl<llvm::Value *> &privateReductionVariables,
+    DenseMap<Value, llvm::Value *> &reductionVariableMap) {
+  llvm::LLVMContext &Context = builder.getContext();
+  llvm::Type *OpaquePtrTy = llvm::PointerType::get(Context, 0);
+  if (region.empty()) {
+    return llvm::Constant::getNullValue(OpaquePtrTy);
+  }
+  llvm::FunctionType *funcType = nullptr;
+  if (isByRef[Cnt])
+    funcType = llvm::FunctionType::get(builder.getVoidTy(),
+                                       {OpaquePtrTy, OpaquePtrTy}, false);
+  else
+    funcType =
+        llvm::FunctionType::get(OpaquePtrTy, {OpaquePtrTy, OpaquePtrTy}, false);
+  llvm::Function *function =
+      llvm::Function::Create(funcType, llvm::Function::ExternalLinkage, name,
+                             builder.GetInsertBlock()->getModule());
+  function->setDoesNotRecurse();
+  llvm::BasicBlock *entry =
+      llvm::BasicBlock::Create(Context, "entry", function);
+  llvm::IRBuilder<> bbBuilder(entry);
+
+  llvm::Value *arg0 = function->getArg(0);
+  llvm::Value *arg1 = function->getArg(1);
+
+  if (name == "red_init") {
+    function->addParamAttr(0, llvm::Attribute::NoAlias);
+    function->addParamAttr(1, llvm::Attribute::NoAlias);
+    if (isByRef[Cnt]) {
+      // TODO: Handle case where the initializer uses initialization from
+      // declare reduction construct using `arg1Alloca`.
+      llvm::AllocaInst *arg0Alloca =
+          bbBuilder.CreateAlloca(bbBuilder.getPtrTy());
+      llvm::AllocaInst *arg1Alloca =
+          bbBuilder.CreateAlloca(bbBuilder.getPtrTy());
+      bbBuilder.CreateStore(arg0, arg0Alloca);
+      bbBuilder.CreateStore(arg1, arg1Alloca);
+      llvm::Value *LoadVal =
----------------
ergawy wrote:

Isn't this the same value as `arg0`? Why the need for loads, stores, and allocas? I must be missing something, just want to understand more. Same applies to the `red_comd` region.

https://github.com/llvm/llvm-project/pull/120957