d3d96e2057
Both clang and gfortran support the -fopenmp-simd flag, which enables OpenMP support only for simd constructs, while disabling the rest of OpenMP. Implement the appropriate parse tree rewriting to remove non-SIMD OpenMP constructs at the parsing stage. Add a new SimdOnly flang OpenMP IR pass which rewrites generated OpenMP FIR to handle untangling composite simd constructs, and clean up OpenMP operations leftover after the parse tree rewriting stage. With this approach, the two parts of the logic required to make the flag work can be self-contained within the parse tree rewriter and the MLIR pass, respectively. It does not need to be implemented within the core lowering logic itself. The flag is expected to have no effect if -fopenmp is passed explicitly, and is only expected to remove OpenMP constructs, not things like OpenMP library functions calls. This matches the behaviour of other compilers. --------- Signed-off-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
213 lines
8.1 KiB
C++
213 lines
8.1 KiB
C++
//===-- SimdOnly.cpp ------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "flang/Optimizer/Builder/FIRBuilder.h"
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#include "mlir/Dialect/Arith/IR/Arith.h"
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#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
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#include "mlir/Dialect/Func/IR/FuncOps.h"
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#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
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#include "mlir/IR/MLIRContext.h"
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#include "mlir/IR/Operation.h"
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#include "mlir/IR/PatternMatch.h"
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#include "mlir/Pass/Pass.h"
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#include "mlir/Support/LLVM.h"
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#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
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#include "llvm/Support/Debug.h"
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namespace flangomp {
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#define GEN_PASS_DEF_SIMDONLYPASS
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#include "flang/Optimizer/OpenMP/Passes.h.inc"
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} // namespace flangomp
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namespace {
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#define DEBUG_TYPE "omp-simd-only-pass"
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/// Rewrite and remove OpenMP operations left after the parse tree rewriting for
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/// -fopenmp-simd is done. If possible, OpenMP constructs should be rewritten at
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/// the parse tree stage. This pass is supposed to only handle complexities
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/// around untangling composite simd constructs, and perform the necessary
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/// cleanup.
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class SimdOnlyConversionPattern : public mlir::RewritePattern {
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public:
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SimdOnlyConversionPattern(mlir::MLIRContext *ctx)
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: mlir::RewritePattern(MatchAnyOpTypeTag{}, 1, ctx) {}
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mlir::LogicalResult
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matchAndRewrite(mlir::Operation *op,
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mlir::PatternRewriter &rewriter) const override {
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if (op->getDialect()->getNamespace() !=
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mlir::omp::OpenMPDialect::getDialectNamespace())
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return rewriter.notifyMatchFailure(op, "Not an OpenMP op");
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if (auto simdOp = mlir::dyn_cast<mlir::omp::SimdOp>(op)) {
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// Remove the composite attr given that the op will no longer be composite
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if (simdOp.isComposite()) {
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simdOp.setComposite(false);
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return mlir::success();
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}
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return rewriter.notifyMatchFailure(op, "Op is a plain SimdOp");
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}
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if (op->getParentOfType<mlir::omp::SimdOp>() &&
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(mlir::isa<mlir::omp::YieldOp>(op) ||
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mlir::isa<mlir::omp::ScanOp>(op) ||
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mlir::isa<mlir::omp::LoopNestOp>(op) ||
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mlir::isa<mlir::omp::TerminatorOp>(op)))
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return rewriter.notifyMatchFailure(op, "Op is part of a simd construct");
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if (!mlir::isa<mlir::func::FuncOp>(op->getParentOp()) &&
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(mlir::isa<mlir::omp::TerminatorOp>(op) ||
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mlir::isa<mlir::omp::YieldOp>(op)))
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return rewriter.notifyMatchFailure(op,
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"Non top-level yield or terminator");
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LLVM_DEBUG(llvm::dbgs() << "SimdOnlyPass matched OpenMP op:\n");
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LLVM_DEBUG(op->dump());
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auto eraseUnlessUsedBySimd = [&](mlir::Operation *ompOp,
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mlir::StringAttr name) {
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if (auto uses =
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mlir::SymbolTable::getSymbolUses(name, op->getParentOp())) {
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for (auto &use : *uses)
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if (mlir::isa<mlir::omp::SimdOp>(use.getUser()))
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return rewriter.notifyMatchFailure(op,
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"Op used by a simd construct");
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}
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rewriter.eraseOp(ompOp);
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return mlir::success();
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};
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if (auto ompOp = mlir::dyn_cast<mlir::omp::PrivateClauseOp>(op))
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return eraseUnlessUsedBySimd(ompOp, ompOp.getSymNameAttr());
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if (auto ompOp = mlir::dyn_cast<mlir::omp::DeclareReductionOp>(op))
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return eraseUnlessUsedBySimd(ompOp, ompOp.getSymNameAttr());
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// Might be left over from rewriting composite simd with target map
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if (mlir::isa<mlir::omp::MapBoundsOp>(op)) {
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rewriter.eraseOp(op);
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return mlir::success();
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}
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if (auto mapInfoOp = mlir::dyn_cast<mlir::omp::MapInfoOp>(op)) {
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mapInfoOp.getResult().replaceAllUsesWith(mapInfoOp.getVarPtr());
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rewriter.eraseOp(mapInfoOp);
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return mlir::success();
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}
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// Might be leftover after parse tree rewriting
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if (auto threadPrivateOp = mlir::dyn_cast<mlir::omp::ThreadprivateOp>(op)) {
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threadPrivateOp.getTlsAddr().replaceAllUsesWith(
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threadPrivateOp.getSymAddr());
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rewriter.eraseOp(threadPrivateOp);
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return mlir::success();
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}
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fir::FirOpBuilder builder(rewriter, op);
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mlir::Location loc = op->getLoc();
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auto inlineSimpleOp = [&](mlir::Operation *ompOp) -> bool {
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if (!ompOp)
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return false;
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assert("OpenMP operation has one region" && ompOp->getNumRegions() == 1);
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llvm::SmallVector<std::pair<mlir::Value, mlir::BlockArgument>>
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blockArgsPairs;
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if (auto iface =
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mlir::dyn_cast<mlir::omp::BlockArgOpenMPOpInterface>(op)) {
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iface.getBlockArgsPairs(blockArgsPairs);
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for (auto [value, argument] : blockArgsPairs)
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rewriter.replaceAllUsesWith(argument, value);
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}
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if (ompOp->getRegion(0).getBlocks().size() == 1) {
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auto &block = *ompOp->getRegion(0).getBlocks().begin();
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// This block is about to be removed so any arguments should have been
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// replaced by now.
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block.eraseArguments(0, block.getNumArguments());
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if (auto terminatorOp =
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mlir::dyn_cast<mlir::omp::TerminatorOp>(block.back())) {
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rewriter.eraseOp(terminatorOp);
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}
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rewriter.inlineBlockBefore(&block, ompOp, {});
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} else {
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// When dealing with multi-block regions we need to fix up the control
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// flow
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auto *origBlock = ompOp->getBlock();
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auto *newBlock = rewriter.splitBlock(origBlock, ompOp->getIterator());
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auto *innerFrontBlock = &ompOp->getRegion(0).getBlocks().front();
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builder.setInsertionPointToEnd(origBlock);
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mlir::cf::BranchOp::create(builder, loc, innerFrontBlock);
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// We are no longer passing any arguments to the first block in the
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// region, so this should be safe to erase.
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innerFrontBlock->eraseArguments(0, innerFrontBlock->getNumArguments());
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for (auto &innerBlock : ompOp->getRegion(0).getBlocks()) {
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// Remove now-unused block arguments
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for (auto arg : innerBlock.getArguments()) {
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if (arg.getUses().empty())
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innerBlock.eraseArgument(arg.getArgNumber());
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}
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if (auto terminatorOp =
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mlir::dyn_cast<mlir::omp::TerminatorOp>(innerBlock.back())) {
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builder.setInsertionPointToEnd(&innerBlock);
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mlir::cf::BranchOp::create(builder, loc, newBlock);
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rewriter.eraseOp(terminatorOp);
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}
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}
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rewriter.inlineRegionBefore(ompOp->getRegion(0), newBlock);
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}
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rewriter.eraseOp(op);
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return true;
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};
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// Remove ops that will be surrounding simd once a composite simd construct
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// goes through the codegen stage. All of the other ones should have alredy
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// been removed in the parse tree rewriting stage.
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if (inlineSimpleOp(mlir::dyn_cast<mlir::omp::TeamsOp>(op)) ||
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inlineSimpleOp(mlir::dyn_cast<mlir::omp::ParallelOp>(op)) ||
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inlineSimpleOp(mlir::dyn_cast<mlir::omp::TargetOp>(op)) ||
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inlineSimpleOp(mlir::dyn_cast<mlir::omp::WsloopOp>(op)) ||
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inlineSimpleOp(mlir::dyn_cast<mlir::omp::DistributeOp>(op)))
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return mlir::success();
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op->emitOpError("left unhandled after SimdOnly pass.");
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return mlir::failure();
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}
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};
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class SimdOnlyPass : public flangomp::impl::SimdOnlyPassBase<SimdOnlyPass> {
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public:
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SimdOnlyPass() = default;
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void runOnOperation() override {
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mlir::ModuleOp module = getOperation();
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mlir::MLIRContext *context = &getContext();
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mlir::RewritePatternSet patterns(context);
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patterns.insert<SimdOnlyConversionPattern>(context);
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mlir::GreedyRewriteConfig config;
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// Prevent the pattern driver from merging blocks.
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config.setRegionSimplificationLevel(
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mlir::GreedySimplifyRegionLevel::Disabled);
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if (mlir::failed(
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mlir::applyPatternsGreedily(module, std::move(patterns), config))) {
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mlir::emitError(module.getLoc(), "Error in SimdOnly conversion pass");
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signalPassFailure();
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}
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}
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};
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} // namespace
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