[flang-commits] [flang] bf812c1 - [flang][OpenMP] Added initial support for lowering OpenMP parallel construct

[Sourabh Singh Tomar via flang-commits]

Author: Sourabh Singh Tomar
Date: 2020-07-31T23:59:46+05:30
New Revision: bf812c145ca2edc4fb76133ec8104267d66f8ee6

URL: https://github.com/llvm/llvm-project/commit/bf812c145ca2edc4fb76133ec8104267d66f8ee6
DIFF: https://github.com/llvm/llvm-project/commit/bf812c145ca2edc4fb76133ec8104267d66f8ee6.diff

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

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

Reviewed By: kiranchandramohan, DavidTruby

Differential Revision: https://reviews.llvm.org/D84965

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/flang/lib/Lower/OpenMP.cpp b/flang/lib/Lower/OpenMP.cpp
index bc7cd27df320..017187069dcb 100644
--- a/flang/lib/Lower/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP.cpp
@@ -75,6 +75,36 @@ genOMP(Fortran::lower::AbstractConverter &absConv,
       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 @@ void Fortran::lower::genOpenMPConstruct(
             TODO();
           },
           [&](const Fortran::parser::OpenMPBlockConstruct &blockConstruct) {
-            TODO();
+            genOMP(absConv, eval, blockConstruct);
           },
           [&](const Fortran::parser::OpenMPAtomicConstruct &atomicConstruct) {
             TODO();

diff  --git a/flang/unittests/Lower/OpenMPLoweringTest.cpp b/flang/unittests/Lower/OpenMPLoweringTest.cpp
index fd580d71fab3..ad6fe739d16b 100644
--- a/flang/unittests/Lower/OpenMPLoweringTest.cpp
+++ b/flang/unittests/Lower/OpenMPLoweringTest.cpp
@@ -71,4 +71,31 @@ TEST_F(OpenMPLoweringTest, TaskYield) {
   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