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