1 //===- AffineParallelize.cpp - Affineparallelize Pass---------------------===//
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 // This file implements a parallelizer for affine loop nests that is able to
10 // perform inner or outer loop parallelization.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "PassDetail.h"
15 #include "mlir/Analysis/AffineStructures.h"
16 #include "mlir/Analysis/LoopAnalysis.h"
17 #include "mlir/Analysis/Utils.h"
18 #include "mlir/Dialect/Affine/IR/AffineOps.h"
19 #include "mlir/Dialect/Affine/IR/AffineValueMap.h"
20 #include "mlir/Dialect/Affine/Passes.h"
21 #include "mlir/Dialect/Affine/Passes.h.inc"
22 #include "mlir/Dialect/Affine/Utils.h"
23 #include "mlir/Transforms/LoopUtils.h"
24 #include "llvm/Support/Debug.h"
25 #include <deque>
26 
27 #define DEBUG_TYPE "affine-parallel"
28 
29 using namespace mlir;
30 
31 namespace {
32 /// Convert all parallel affine.for op into 1-D affine.parallel op.
33 struct AffineParallelize : public AffineParallelizeBase<AffineParallelize> {
34   void runOnFunction() override;
35 };
36 } // namespace
37 
38 void AffineParallelize::runOnFunction() {
39   FuncOp f = getFunction();
40 
41   // The walker proceeds in post-order, but we need to process outer loops first
42   // to control the number of outer parallel loops, so push candidate loops to
43   // the front of a deque.
44   std::deque<AffineForOp> parallelizableLoops;
45   f.walk([&](AffineForOp loop) {
46     if (isLoopParallel(loop))
47       parallelizableLoops.push_front(loop);
48   });
49 
50   for (AffineForOp loop : parallelizableLoops) {
51     unsigned numParentParallelOps = 0;
52     for (Operation *op = loop->getParentOp();
53          op != nullptr && !op->hasTrait<OpTrait::AffineScope>();
54          op = op->getParentOp()) {
55       if (isa<AffineParallelOp>(op))
56         ++numParentParallelOps;
57     }
58 
59     if (numParentParallelOps < maxNested)
60       affineParallelize(loop);
61   }
62 }
63 
64 std::unique_ptr<OperationPass<FuncOp>> mlir::createAffineParallelizePass() {
65   return std::make_unique<AffineParallelize>();
66 }
67