1 //===- ForallToParallel.cpp - scf.forall to scf.parallel loop conversion --===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Transforms SCF.ForallOp's into SCF.ParallelOps's.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "mlir/Dialect/SCF/IR/SCF.h"
14 #include "mlir/Dialect/SCF/Transforms/Passes.h"
15 #include "mlir/Dialect/SCF/Transforms/Transforms.h"
16 #include "mlir/IR/PatternMatch.h"
17
18 namespace mlir {
19 #define GEN_PASS_DEF_SCFFORALLTOPARALLELLOOP
20 #include "mlir/Dialect/SCF/Transforms/Passes.h.inc"
21 } // namespace mlir
22
23 using namespace mlir;
24
forallToParallelLoop(RewriterBase & rewriter,scf::ForallOp forallOp,scf::ParallelOp * result)25 LogicalResult mlir::scf::forallToParallelLoop(RewriterBase &rewriter,
26 scf::ForallOp forallOp,
27 scf::ParallelOp *result) {
28 OpBuilder::InsertionGuard guard(rewriter);
29 rewriter.setInsertionPoint(forallOp);
30
31 Location loc = forallOp.getLoc();
32 if (!forallOp.getOutputs().empty())
33 return rewriter.notifyMatchFailure(
34 forallOp,
35 "only fully bufferized scf.forall ops can be lowered to scf.parallel");
36
37 // Convert mixed bounds and steps to SSA values.
38 SmallVector<Value> lbs = forallOp.getLowerBound(rewriter);
39 SmallVector<Value> ubs = forallOp.getUpperBound(rewriter);
40 SmallVector<Value> steps = forallOp.getStep(rewriter);
41
42 // Create empty scf.parallel op.
43 auto parallelOp = rewriter.create<scf::ParallelOp>(loc, lbs, ubs, steps);
44 rewriter.eraseBlock(¶llelOp.getRegion().front());
45 rewriter.inlineRegionBefore(forallOp.getRegion(), parallelOp.getRegion(),
46 parallelOp.getRegion().begin());
47 // Replace the terminator.
48 rewriter.setInsertionPointToEnd(¶llelOp.getRegion().front());
49 rewriter.replaceOpWithNewOp<scf::ReduceOp>(
50 parallelOp.getRegion().front().getTerminator());
51
52 // If the mapping attribute is present, propagate to the new parallelOp.
53 if (forallOp.getMapping())
54 parallelOp->setAttr("mapping", *forallOp.getMapping());
55
56 // Erase the scf.forall op.
57 rewriter.replaceOp(forallOp, parallelOp);
58
59 if (result)
60 *result = parallelOp;
61
62 return success();
63 }
64
65 namespace {
66 struct ForallToParallelLoop final
67 : public impl::SCFForallToParallelLoopBase<ForallToParallelLoop> {
runOnOperation__anonc6d64d9a0111::ForallToParallelLoop68 void runOnOperation() override {
69 Operation *parentOp = getOperation();
70 IRRewriter rewriter(parentOp->getContext());
71
72 parentOp->walk([&](scf::ForallOp forallOp) {
73 if (failed(scf::forallToParallelLoop(rewriter, forallOp))) {
74 return signalPassFailure();
75 }
76 });
77 }
78 };
79 } // namespace
80
createForallToParallelLoopPass()81 std::unique_ptr<Pass> mlir::createForallToParallelLoopPass() {
82 return std::make_unique<ForallToParallelLoop>();
83 }
84