1 //= TestAffineLoopParametricTiling.cpp -- Parametric Affine loop tiling 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 test pass to test parametric tiling of perfectly
10 // nested affine for loops.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "mlir/Dialect/Affine/IR/AffineOps.h"
15 #include "mlir/Dialect/Affine/Passes.h"
16 #include "mlir/Transforms/LoopUtils.h"
17 
18 using namespace mlir;
19 
20 #define DEBUG_TYPE "test-affine-parametric-tile"
21 
22 namespace {
23 struct TestAffineLoopParametricTiling
24     : public PassWrapper<TestAffineLoopParametricTiling, FunctionPass> {
25   StringRef getArgument() const final { return "test-affine-parametric-tile"; }
26   StringRef getDescription() const final {
27     return "Tile affine loops using SSA values as tile sizes";
28   }
29   void runOnFunction() override;
30 };
31 } // end anonymous namespace
32 
33 /// Checks if the function enclosing the loop nest has any arguments passed to
34 /// it, which can be used as tiling parameters. Assumes that atleast 'n'
35 /// arguments are passed, where 'n' is the number of loops in the loop nest.
36 static void checkIfTilingParametersExist(ArrayRef<AffineForOp> band) {
37   assert(!band.empty() && "no loops in input band");
38   AffineForOp topLoop = band[0];
39 
40   if (FuncOp funcOp = dyn_cast<FuncOp>(topLoop->getParentOp()))
41     assert(funcOp.getNumArguments() >= band.size() && "Too few tile sizes");
42 }
43 
44 /// Captures tiling parameters, which are expected to be passed as arguments
45 /// to the function enclosing the loop nest. Also checks if the required
46 /// parameters are of index type. This approach is temporary for testing
47 /// purposes.
48 static void getTilingParameters(ArrayRef<AffineForOp> band,
49                                 SmallVectorImpl<Value> &tilingParameters) {
50   AffineForOp topLoop = band[0];
51   Region *funcOpRegion = topLoop->getParentRegion();
52   unsigned nestDepth = band.size();
53 
54   for (BlockArgument blockArgument :
55        funcOpRegion->getArguments().take_front(nestDepth)) {
56     if (blockArgument.getArgNumber() < nestDepth) {
57       assert(blockArgument.getType().isIndex() &&
58              "expected tiling parameters to be of index type.");
59       tilingParameters.push_back(blockArgument);
60     }
61   }
62 }
63 
64 void TestAffineLoopParametricTiling::runOnFunction() {
65   // Bands of loops to tile.
66   std::vector<SmallVector<AffineForOp, 6>> bands;
67   getTileableBands(getFunction(), &bands);
68 
69   // Tile each band.
70   for (SmallVectorImpl<AffineForOp> &band : bands) {
71     // Capture the tiling parameters from the arguments to the function
72     // enclosing this loop nest.
73     SmallVector<AffineForOp, 6> tiledNest;
74     SmallVector<Value, 6> tilingParameters;
75     // Check if tiling parameters are present.
76     checkIfTilingParametersExist(band);
77 
78     // Get function arguments as tiling parameters.
79     getTilingParameters(band, tilingParameters);
80 
81     if (failed(
82             tilePerfectlyNestedParametric(band, tilingParameters, &tiledNest)))
83       return signalPassFailure();
84   }
85 }
86 
87 namespace mlir {
88 namespace test {
89 void registerTestAffineLoopParametricTilingPass() {
90   PassRegistration<TestAffineLoopParametricTiling>();
91 }
92 } // namespace test
93 } // namespace mlir
94