[PATCH] D84965: [flang][OpenMP] Added initial support for lowering OpenMP parallel construct

[Sourabh Singh Tomar via Phabricator via llvm-commits]

SouraVX created this revision.
SouraVX added reviewers: kiranchandramohan, schweitz, jdoerfert, clementval, kiranktp.
Herald added subscribers: llvm-commits, guansong, yaxunl.
Herald added a reviewer: DavidTruby.
Herald added a project: LLVM.
SouraVX requested review of this revision.
Herald added a subscriber: sstefan1.

This patch lower `!OMP PARALLEL` construct from PFT to OpenMPDialect operations.
This is first patch in this direction(lowering parallel construct).

OpenMP parallel construct can have multiple clauses and parameters. This patch
only implements lowering of an empty(contains no code in body) parallel construct
without any clauses or parameters.

Patch is carved out of following approved PR:
https://github.com/flang-compiler/f18-llvm-project/pull/322


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84965

Files:
  flang/lib/Lower/OpenMP.cpp
  flang/unittests/Lower/OpenMPLoweringTest.cpp


Index: flang/unittests/Lower/OpenMPLoweringTest.cpp
===================================================================
--- flang/unittests/Lower/OpenMPLoweringTest.cpp
+++ flang/unittests/Lower/OpenMPLoweringTest.cpp
@@ -71,4 +71,31 @@
   EXPECT_EQ(succeeded(taskYieldOp.verify()), true);
 }
 
+TEST_F(OpenMPLoweringTest, EmptyParallel) {
+  // Construct a dummy parse tree node for `!OMP parallel`.
+  struct Fortran::parser::OmpSimpleStandaloneDirective parallelDirective(
+      llvm::omp::Directive::OMPD_parallel);
+
+  // Check and lower the `!OMP parallel` node to `ParallelOp` operation of
+  // OpenMPDialect.
+  EXPECT_EQ(parallelDirective.v, llvm::omp::Directive::OMPD_parallel);
+  auto insertPt = mlirOpBuilder->saveInsertionPoint();
+  llvm::ArrayRef<mlir::Type> argTy;
+  mlir::ValueRange range;
+  llvm::SmallVector<int32_t, 6> operandSegmentSizes(6 /*Size=*/, 0 /*Value=*/);
+  // create and insert the operation.
+  auto parallelOp = mlirOpBuilder->create<mlir::omp::ParallelOp>(
+      mlirOpBuilder->getUnknownLoc(), argTy, range);
+  parallelOp.setAttr(mlir::omp::ParallelOp::getOperandSegmentSizeAttr(),
+      mlirOpBuilder->getI32VectorAttr(operandSegmentSizes));
+  parallelOp.getRegion().push_back(new mlir::Block{});
+  auto &block = parallelOp.getRegion().back();
+  mlirOpBuilder->setInsertionPointToStart(&block);
+  // ensure the block is well-formed.
+  mlirOpBuilder->create<mlir::omp::TerminatorOp>(
+      mlirOpBuilder->getUnknownLoc());
+  mlirOpBuilder->restoreInsertionPoint(insertPt);
+  EXPECT_EQ(succeeded(parallelOp.verify()), true);
+}
+
 // main() from gtest_main
Index: flang/lib/Lower/OpenMP.cpp
===================================================================
--- flang/lib/Lower/OpenMP.cpp
+++ flang/lib/Lower/OpenMP.cpp
@@ -75,6 +75,36 @@
       standaloneConstruct.u);
 }
 
+static void
+genOMP(Fortran::lower::AbstractConverter &absConv,
+       Fortran::lower::pft::Evaluation &eval,
+       const Fortran::parser::OpenMPBlockConstruct &blockConstruct) {
+  const auto &blockDirective =
+      std::get<Fortran::parser::OmpBeginBlockDirective>(blockConstruct.t);
+  const auto &parallelDirective =
+      std::get<Fortran::parser::OmpBlockDirective>(blockDirective.t);
+  if (parallelDirective.v == llvm::omp::OMPD_parallel) {
+    auto &firOpBuilder = absConv.getFirOpBuilder();
+    auto currentLocation = absConv.getCurrentLocation();
+    auto insertPt = firOpBuilder.saveInsertionPoint();
+    llvm::ArrayRef<mlir::Type> argTy;
+    mlir::ValueRange range;
+    llvm::SmallVector<int32_t, 6> operandSegmentSizes(6 /*Size=*/,
+                                                      0 /*Value=*/);
+    // create and insert the operation.
+    auto parallelOp = firOpBuilder.create<mlir::omp::ParallelOp>(
+        currentLocation, argTy, range);
+    parallelOp.setAttr(mlir::omp::ParallelOp::getOperandSegmentSizeAttr(),
+                       firOpBuilder.getI32VectorAttr(operandSegmentSizes));
+    parallelOp.getRegion().push_back(new Block{});
+    auto &block = parallelOp.getRegion().back();
+    firOpBuilder.setInsertionPointToStart(&block);
+    // ensure the block is well-formed.
+    firOpBuilder.create<mlir::omp::TerminatorOp>(currentLocation);
+    firOpBuilder.restoreInsertionPoint(insertPt);
+  }
+}
+
 void Fortran::lower::genOpenMPConstruct(
     Fortran::lower::AbstractConverter &absConv,
     Fortran::lower::pft::Evaluation &eval,
@@ -92,7 +122,7 @@
             TODO();
           },
           [&](const Fortran::parser::OpenMPBlockConstruct &blockConstruct) {
-            TODO();
+            genOMP(absConv, eval, blockConstruct);
           },
           [&](const Fortran::parser::OpenMPAtomicConstruct &atomicConstruct) {
             TODO();


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