[Mlir-commits] [mlir] 119545f - [mlir] Add conversion from SCF parallel loops to OpenMP
Alex Zinenko
llvmlistbot at llvm.org
Tue Nov 24 12:13:04 PST 2020
Author: Alex Zinenko
Date: 2020-11-24T21:12:56+01:00
New Revision: 119545f4338efacabf99e06eeca965913f6617f2
URL: https://github.com/llvm/llvm-project/commit/119545f4338efacabf99e06eeca965913f6617f2
DIFF: https://github.com/llvm/llvm-project/commit/119545f4338efacabf99e06eeca965913f6617f2.diff
LOG: [mlir] Add conversion from SCF parallel loops to OpenMP
Introduce a conversion pass from SCF parallel loops to OpenMP dialect
constructs - parallel region and workshare loop. Loops with reductions are not
supported because the OpenMP dialect cannot model them yet.
The conversion currently targets only one level of parallelism, i.e. only
one top-level `omp.parallel` operation is produced even if there are nested
`scf.parallel` operations that could be mapped to `omp.wsloop`. Nested
parallelism support is left for future work.
Reviewed By: kiranchandramohan
Differential Revision: https://reviews.llvm.org/D91982
Added:
mlir/include/mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h
mlir/lib/Conversion/SCFToOpenMP/CMakeLists.txt
mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
mlir/test/Conversion/SCFToOpenMP/scf-to-openmp.mlir
Modified:
mlir/include/mlir/Conversion/Passes.h
mlir/include/mlir/Conversion/Passes.td
mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td
mlir/lib/Conversion/CMakeLists.txt
mlir/lib/Conversion/PassDetail.h
mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
Removed:
################################################################################
diff --git a/mlir/include/mlir/Conversion/Passes.h b/mlir/include/mlir/Conversion/Passes.h
index b1d2da9bab2c..0d2281f99581 100644
--- a/mlir/include/mlir/Conversion/Passes.h
+++ b/mlir/include/mlir/Conversion/Passes.h
@@ -23,6 +23,7 @@
#include "mlir/Conversion/OpenMPToLLVM/ConvertOpenMPToLLVM.h"
#include "mlir/Conversion/PDLToPDLInterp/PDLToPDLInterp.h"
#include "mlir/Conversion/SCFToGPU/SCFToGPUPass.h"
+#include "mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h"
#include "mlir/Conversion/SCFToStandard/SCFToStandard.h"
#include "mlir/Conversion/SPIRVToLLVM/ConvertSPIRVToLLVMPass.h"
#include "mlir/Conversion/ShapeToStandard/ShapeToStandard.h"
diff --git a/mlir/include/mlir/Conversion/Passes.td b/mlir/include/mlir/Conversion/Passes.td
index 7c61fad9ff2f..fdf01b7f93d0 100644
--- a/mlir/include/mlir/Conversion/Passes.td
+++ b/mlir/include/mlir/Conversion/Passes.td
@@ -230,6 +230,17 @@ def ConvertPDLToPDLInterp : Pass<"convert-pdl-to-pdl-interp", "ModuleOp"> {
let dependentDialects = ["pdl_interp::PDLInterpDialect"];
}
+//===----------------------------------------------------------------------===//
+// SCFToOpenMP
+//===----------------------------------------------------------------------===//
+
+def ConvertSCFToOpenMP : FunctionPass<"convert-scf-to-openmp"> {
+ let summary = "Convert SCF parallel loop to OpenMP parallel + workshare "
+ "constructs.";
+ let constructor = "mlir::createConvertSCFToOpenMPPass()";
+ let dependentDialects = ["omp::OpenMPDialect"];
+}
+
//===----------------------------------------------------------------------===//
// SCFToStandard
//===----------------------------------------------------------------------===//
diff --git a/mlir/include/mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h b/mlir/include/mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h
new file mode 100644
index 000000000000..349c4e1efc83
--- /dev/null
+++ b/mlir/include/mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h
@@ -0,0 +1,23 @@
+//===- ConvertSCFToOpenMP.h - SCF to OpenMP pass entrypoint -----*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_SCFTOOPENMP_SCFTOOPENMP_H
+#define MLIR_CONVERSION_SCFTOOPENMP_SCFTOOPENMP_H
+
+#include <memory>
+
+namespace mlir {
+class FuncOp;
+template <typename T>
+class OperationPass;
+
+std::unique_ptr<OperationPass<FuncOp>> createConvertSCFToOpenMPPass();
+
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_SCFTOOPENMP_SCFTOOPENMP_H
diff --git a/mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td b/mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td
index d42466af9e17..f915afcf32c9 100644
--- a/mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td
+++ b/mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td
@@ -92,6 +92,9 @@ def ParallelOp : OpenMP_Op<"parallel", [AttrSizedOperandSegments]> {
let regions = (region AnyRegion:$region);
+ let builders = [
+ OpBuilderDAG<(ins CArg<"ArrayRef<NamedAttribute>", "{}">:$attributes)>
+ ];
let parser = [{ return parseParallelOp(parser, result); }];
let printer = [{ return printParallelOp(p, *this); }];
let verifier = [{ return ::verifyParallelOp(*this); }];
@@ -175,6 +178,12 @@ def WsLoopOp : OpenMP_Op<"wsloop", [AttrSizedOperandSegments]> {
Confined<OptionalAttr<I64Attr>, [IntMinValue<0>]>:$ordered_val,
OptionalAttr<OrderKind>:$order_val);
+ let builders = [
+ OpBuilderDAG<(ins "ValueRange":$lowerBound, "ValueRange":$upperBound,
+ "ValueRange":$step,
+ CArg<"ArrayRef<NamedAttribute>", "{}">:$attributes)>
+ ];
+
let regions = (region AnyRegion:$region);
}
diff --git a/mlir/lib/Conversion/CMakeLists.txt b/mlir/lib/Conversion/CMakeLists.txt
index fa402cc8afe1..bf1789505882 100644
--- a/mlir/lib/Conversion/CMakeLists.txt
+++ b/mlir/lib/Conversion/CMakeLists.txt
@@ -12,6 +12,7 @@ add_subdirectory(LinalgToStandard)
add_subdirectory(OpenMPToLLVM)
add_subdirectory(PDLToPDLInterp)
add_subdirectory(SCFToGPU)
+add_subdirectory(SCFToOpenMP)
add_subdirectory(SCFToSPIRV)
add_subdirectory(SCFToStandard)
add_subdirectory(ShapeToStandard)
diff --git a/mlir/lib/Conversion/PassDetail.h b/mlir/lib/Conversion/PassDetail.h
index bee2f5798a54..6314a5c91d0b 100644
--- a/mlir/lib/Conversion/PassDetail.h
+++ b/mlir/lib/Conversion/PassDetail.h
@@ -33,6 +33,10 @@ namespace NVVM {
class NVVMDialect;
} // end namespace NVVM
+namespace omp {
+class OpenMPDialect;
+} // end namespace omp
+
namespace pdl_interp {
class PDLInterpDialect;
} // end namespace pdl_interp
diff --git a/mlir/lib/Conversion/SCFToOpenMP/CMakeLists.txt b/mlir/lib/Conversion/SCFToOpenMP/CMakeLists.txt
new file mode 100644
index 000000000000..1ef4b74da6dd
--- /dev/null
+++ b/mlir/lib/Conversion/SCFToOpenMP/CMakeLists.txt
@@ -0,0 +1,17 @@
+add_mlir_conversion_library(MLIRSCFToOpenMP
+ SCFToOpenMP.cpp
+
+ ADDITIONAL_HEADER_DIRS
+ ${MLIR_MAIN_INCLUDE_DIR}/mlir/Conversion/SCFToStandard
+
+ DEPENDS
+ MLIRConversionPassIncGen
+
+ LINK_COMPONENTS
+ Core
+
+ LINK_LIBS PUBLIC
+ MLIROpenMP
+ MLIRSCF
+ MLIRTransforms
+ )
diff --git a/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
new file mode 100644
index 000000000000..01e7623e8a49
--- /dev/null
+++ b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
@@ -0,0 +1,113 @@
+//===- SCFToOpenMP.cpp - Structured Control Flow to OpenMP conversion -----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a pass to convert scf.parallel operations into OpenMP
+// parallel loops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/SCFToOpenMP/SCFToOpenMP.h"
+#include "../PassDetail.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+#include "mlir/Dialect/SCF/SCF.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+using namespace mlir;
+
+namespace {
+
+/// Converts SCF parallel operation into an OpenMP workshare loop construct.
+struct ParallelOpLowering : public OpRewritePattern<scf::ParallelOp> {
+ using OpRewritePattern<scf::ParallelOp>::OpRewritePattern;
+
+ LogicalResult matchAndRewrite(scf::ParallelOp parallelOp,
+ PatternRewriter &rewriter) const override {
+ // TODO: add support for reductions when OpenMP loops have them.
+ if (parallelOp.getNumResults() != 0)
+ return rewriter.notifyMatchFailure(
+ parallelOp,
+ "OpenMP dialect does not yet support loops with reductions");
+
+ // Replace SCF yield with OpenMP yield.
+ {
+ OpBuilder::InsertionGuard guard(rewriter);
+ rewriter.setInsertionPointToEnd(parallelOp.getBody());
+ assert(llvm::hasSingleElement(parallelOp.region()) &&
+ "expected scf.parallel to have one block");
+ rewriter.replaceOpWithNewOp<omp::YieldOp>(
+ parallelOp.getBody()->getTerminator(), ValueRange());
+ }
+
+ // Replace the loop.
+ auto loop = rewriter.create<omp::WsLoopOp>(
+ parallelOp.getLoc(), parallelOp.lowerBound(), parallelOp.upperBound(),
+ parallelOp.step());
+ rewriter.inlineRegionBefore(parallelOp.region(), loop.region(),
+ loop.region().begin());
+ rewriter.eraseOp(parallelOp);
+ return success();
+ }
+};
+
+/// Inserts OpenMP "parallel" operations around top-level SCF "parallel"
+/// operations in the given function. This is implemented as a direct IR
+/// modification rather than as a conversion pattern because it does not
+/// modify the top-level operation it matches, which is a requirement for
+/// rewrite patterns.
+//
+// TODO: consider creating nested parallel operations when necessary.
+static void insertOpenMPParallel(FuncOp func) {
+ // Collect top-level SCF "parallel" ops.
+ SmallVector<scf::ParallelOp, 4> topLevelParallelOps;
+ func.walk([&topLevelParallelOps](scf::ParallelOp parallelOp) {
+ // Ignore ops that are already within OpenMP parallel construct.
+ if (!parallelOp.getParentOfType<scf::ParallelOp>())
+ topLevelParallelOps.push_back(parallelOp);
+ });
+
+ // Wrap SCF ops into OpenMP "parallel" ops.
+ for (scf::ParallelOp parallelOp : topLevelParallelOps) {
+ OpBuilder builder(parallelOp);
+ auto omp = builder.create<omp::ParallelOp>(parallelOp.getLoc());
+ Block *block = builder.createBlock(&omp.getRegion());
+ builder.create<omp::TerminatorOp>(parallelOp.getLoc());
+ block->getOperations().splice(
+ block->begin(), parallelOp.getOperation()->getBlock()->getOperations(),
+ parallelOp.getOperation());
+ }
+}
+
+/// Applies the conversion patterns in the given function.
+static LogicalResult applyPatterns(FuncOp func) {
+ ConversionTarget target(*func.getContext());
+ target.addIllegalOp<scf::ParallelOp>();
+ target.addDynamicallyLegalOp<scf::YieldOp>(
+ [](scf::YieldOp op) { return !isa<scf::ParallelOp>(op.getParentOp()); });
+ target.addLegalDialect<omp::OpenMPDialect>();
+
+ OwningRewritePatternList patterns;
+ patterns.insert<ParallelOpLowering>(func.getContext());
+ FrozenRewritePatternList frozen(std::move(patterns));
+ return applyPartialConversion(func, target, frozen);
+}
+
+/// A pass converting SCF operations to OpenMP operations.
+struct SCFToOpenMPPass : public ConvertSCFToOpenMPBase<SCFToOpenMPPass> {
+ /// Pass entry point.
+ void runOnFunction() override {
+ insertOpenMPParallel(getFunction());
+ if (failed(applyPatterns(getFunction())))
+ signalPassFailure();
+ }
+};
+
+} // end namespace
+
+std::unique_ptr<OperationPass<FuncOp>> mlir::createConvertSCFToOpenMPPass() {
+ return std::make_unique<SCFToOpenMPPass>();
+}
diff --git a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
index 7ab4534f924a..f4b76b635128 100644
--- a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
+++ b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
@@ -37,6 +37,17 @@ void OpenMPDialect::initialize() {
// ParallelOp
//===----------------------------------------------------------------------===//
+void ParallelOp::build(OpBuilder &builder, OperationState &state,
+ ArrayRef<NamedAttribute> attributes) {
+ ParallelOp::build(
+ builder, state, /*if_expr_var=*/nullptr, /*num_threads_var=*/nullptr,
+ /*default_val=*/nullptr, /*private_vars=*/ValueRange(),
+ /*firstprivate_vars=*/ValueRange(), /*shared_vars=*/ValueRange(),
+ /*copyin_vars=*/ValueRange(), /*allocate_vars=*/ValueRange(),
+ /*allocators_vars=*/ValueRange(), /*proc_bind_val=*/nullptr);
+ state.addAttributes(attributes);
+}
+
/// Parse a list of operands with types.
///
/// operand-and-type-list ::= `(` ssa-id-and-type-list `)`
@@ -362,5 +373,22 @@ static ParseResult parseParallelOp(OpAsmParser &parser,
return success();
}
+//===----------------------------------------------------------------------===//
+// WsLoopOp
+//===----------------------------------------------------------------------===//
+
+void WsLoopOp::build(OpBuilder &builder, OperationState &state,
+ ValueRange lowerBound, ValueRange upperBound,
+ ValueRange step, ArrayRef<NamedAttribute> attributes) {
+ build(builder, state, TypeRange(), lowerBound, upperBound, step,
+ /*private_vars=*/ValueRange(),
+ /*firstprivate_vars=*/ValueRange(), /*lastprivate_vars=*/ValueRange(),
+ /*linear_vars=*/ValueRange(), /*linear_step_vars=*/ValueRange(),
+ /*schedule_val=*/nullptr, /*schedule_chunk_var=*/nullptr,
+ /*collapse_val=*/nullptr,
+ /*nowait=*/nullptr, /*ordered_val=*/nullptr, /*order_val=*/nullptr);
+ state.addAttributes(attributes);
+}
+
#define GET_OP_CLASSES
#include "mlir/Dialect/OpenMP/OpenMPOps.cpp.inc"
diff --git a/mlir/test/Conversion/SCFToOpenMP/scf-to-openmp.mlir b/mlir/test/Conversion/SCFToOpenMP/scf-to-openmp.mlir
new file mode 100644
index 000000000000..466bd6aa96af
--- /dev/null
+++ b/mlir/test/Conversion/SCFToOpenMP/scf-to-openmp.mlir
@@ -0,0 +1,65 @@
+// RUN: mlir-opt -convert-scf-to-openmp %s | FileCheck %s
+
+// CHECK-LABEL: @parallel
+func @parallel(%arg0: index, %arg1: index, %arg2: index,
+ %arg3: index, %arg4: index, %arg5: index) {
+ // CHECK: omp.parallel {
+ // CHECK: "omp.wsloop"({{.*}}) ( {
+ scf.parallel (%i, %j) = (%arg0, %arg1) to (%arg2, %arg3) step (%arg4, %arg5) {
+ // CHECK: test.payload
+ "test.payload"(%i, %j) : (index, index) -> ()
+ // CHECK: omp.yield
+ // CHECK: }
+ }
+ // CHECK: omp.terminator
+ // CHECK: }
+ return
+}
+
+// CHECK-LABEL: @nested_loops
+func @nested_loops(%arg0: index, %arg1: index, %arg2: index,
+ %arg3: index, %arg4: index, %arg5: index) {
+ // CHECK: omp.parallel {
+ // CHECK: "omp.wsloop"({{.*}}) ( {
+ // CHECK-NOT: omp.parallel
+ scf.parallel (%i) = (%arg0) to (%arg2) step (%arg4) {
+ // CHECK: "omp.wsloop"({{.*}}) ( {
+ scf.parallel (%j) = (%arg1) to (%arg3) step (%arg5) {
+ // CHECK: test.payload
+ "test.payload"(%i, %j) : (index, index) -> ()
+ // CHECK: omp.yield
+ // CHECK: }
+ }
+ // CHECK: omp.yield
+ // CHECK: }
+ }
+ // CHECK: omp.terminator
+ // CHECK: }
+ return
+}
+
+func @adjacent_loops(%arg0: index, %arg1: index, %arg2: index,
+ %arg3: index, %arg4: index, %arg5: index) {
+ // CHECK: omp.parallel {
+ // CHECK: "omp.wsloop"({{.*}}) ( {
+ scf.parallel (%i) = (%arg0) to (%arg2) step (%arg4) {
+ // CHECK: test.payload1
+ "test.payload1"(%i) : (index) -> ()
+ // CHECK: omp.yield
+ // CHECK: }
+ }
+ // CHECK: omp.terminator
+ // CHECK: }
+
+ // CHECK: omp.parallel {
+ // CHECK: "omp.wsloop"({{.*}}) ( {
+ scf.parallel (%j) = (%arg1) to (%arg3) step (%arg5) {
+ // CHECK: test.payload2
+ "test.payload2"(%j) : (index) -> ()
+ // CHECK: omp.yield
+ // CHECK: }
+ }
+ // CHECK: omp.terminator
+ // CHECK: }
+ return
+}
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