[llvm-branch-commits] [flang] [flang] Lower omp.workshare to other omp constructs (PR #101446)

[Tom Eccles via llvm-branch-commits]

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@@ -0,0 +1,399 @@
+//===- LowerWorkshare.cpp - special cases for bufferization -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Lower omp workshare construct.
+//===----------------------------------------------------------------------===//
+
+#include <flang/Optimizer/Builder/FIRBuilder.h>
+#include <flang/Optimizer/Dialect/FIROps.h>
+#include <flang/Optimizer/Dialect/FIRType.h>
+#include <flang/Optimizer/HLFIR/HLFIROps.h>
+#include <flang/Optimizer/OpenMP/Passes.h>
+#include <llvm/ADT/BreadthFirstIterator.h>
+#include <llvm/ADT/STLExtras.h>
+#include <llvm/ADT/SmallVectorExtras.h>
+#include <llvm/ADT/iterator_range.h>
+#include <llvm/Support/ErrorHandling.h>
+#include <mlir/Dialect/Arith/IR/Arith.h>
+#include <mlir/Dialect/LLVMIR/LLVMTypes.h>
+#include <mlir/Dialect/OpenMP/OpenMPClauseOperands.h>
+#include <mlir/Dialect/OpenMP/OpenMPDialect.h>
+#include <mlir/Dialect/SCF/IR/SCF.h>
+#include <mlir/IR/BuiltinOps.h>
+#include <mlir/IR/IRMapping.h>
+#include <mlir/IR/OpDefinition.h>
+#include <mlir/IR/PatternMatch.h>
+#include <mlir/IR/Visitors.h>
+#include <mlir/Interfaces/SideEffectInterfaces.h>
+#include <mlir/Support/LLVM.h>
+#include <mlir/Transforms/GreedyPatternRewriteDriver.h>
+
+#include <variant>
+
+namespace flangomp {
+#define GEN_PASS_DEF_LOWERWORKSHARE
+#include "flang/Optimizer/OpenMP/Passes.h.inc"
+} // namespace flangomp
+
+#define DEBUG_TYPE "lower-workshare"
+
+using namespace mlir;
+
+namespace flangomp {
+bool shouldUseWorkshareLowering(Operation *op) {
+  // TODO this is insufficient, as we could have
+  // omp.parallel {
+  //   omp.workshare {
+  //     omp.parallel {
+  //       hlfir.elemental {}
+  //
+  // Then this hlfir.elemental shall _not_ use the lowering for workshare
+  //
+  // Standard says:
+  //   For a parallel construct, the construct is a unit of work with respect to
+  //   the workshare construct. The statements contained in the parallel
+  //   construct are executed by a new thread team.
+  //
+  // TODO similarly for single, critical, etc. Need to think through the
+  // patterns and implement this function.
+  //
+  return op->getParentOfType<omp::WorkshareOp>();
+}
+} // namespace flangomp
+
+namespace {
+
+struct SingleRegion {
+  Block::iterator begin, end;
+};
+
+static bool mustParallelizeOp(Operation *op) {
+  // TODO as in shouldUseWorkshareLowering we be careful not to pick up
+  // workshare_loop_wrapper in nested omp.parallel ops
+  //
+  // e.g.
+  //
+  // omp.parallel {
+  //   omp.workshare {
+  //     omp.parallel {
+  //       omp.workshare {
+  //         omp.workshare_loop_wrapper {}
+  return op
+      ->walk(
+          [](omp::WorkshareLoopWrapperOp) { return WalkResult::interrupt(); })
+      .wasInterrupted();
+}
+
+static bool isSafeToParallelize(Operation *op) {
+  return isa<hlfir::DeclareOp>(op) || isa<fir::DeclareOp>(op) ||
+         isMemoryEffectFree(op);
+}
+
+static mlir::func::FuncOp createCopyFunc(mlir::Location loc, mlir::Type varType,
----------------
tblah wrote:

Could this re-use `createCopyFunc` from `ClauseProcessor.cpp`? It would be good to only implement copyprivate in one place.

If not, please could you document the difference between workshare copyprivate and the implementation of the copyprivate clause.

https://github.com/llvm/llvm-project/pull/101446