[llvm-branch-commits] [flang] [MLIR][OpenMP] Add Lowering support for OpenMP Declare Mapper directive (PR #117046)

[Tom Eccles via llvm-branch-commits]

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@@ -2701,7 +2701,42 @@ static void
 genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
        semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
        const parser::OpenMPDeclareMapperConstruct &declareMapperConstruct) {
-  TODO(converter.getCurrentLocation(), "OpenMPDeclareMapperConstruct");
+  fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
+  lower::StatementContext stmtCtx;
+  const auto &spec =
+      std::get<parser::OmpDeclareMapperSpecifier>(declareMapperConstruct.t);
+  const auto &mapperName{std::get<std::optional<parser::Name>>(spec.t)};
+  const auto &varType{std::get<parser::TypeSpec>(spec.t)};
+  const auto &varName{std::get<parser::Name>(spec.t)};
+  assert(varType.declTypeSpec->category() ==
+             semantics::DeclTypeSpec::Category::TypeDerived &&
+         "Expected derived type");
+
+  std::string mapperNameStr;
+  if (mapperName.has_value())
+    mapperNameStr = mapperName->ToString();
+  else
+    mapperNameStr =
+        "default_" + varType.declTypeSpec->derivedTypeSpec().name().ToString();
+
+  mlir::OpBuilder::InsertPoint insPt = firOpBuilder.saveInsertionPoint();
+  firOpBuilder.setInsertionPointToStart(converter.getModuleOp().getBody());
+  auto mlirType = converter.genType(varType.declTypeSpec->derivedTypeSpec());
+  auto varVal = firOpBuilder.createTemporaryAlloc(
+      converter.getCurrentLocation(), mlirType, varName.ToString());
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tblah wrote:

Sorry I didn't notice this before.

So far as I understand, this will create the `fir.alloca` and `hlfir.declare` at the beginning of the MLIR module, not nested in any intermediate operation.

How do you intend to lower this to LLVMIR? We would normally nest these in some kind of "function-like" wrapper operation e.g. `func.func` `fir.global` `omp.private` etc. I wonder if the declare mapper operation needs a nested region for this allocation (like we do for `omp.private` and `omp.declare_reduction`).

https://github.com/llvm/llvm-project/pull/117046