1 //===- CodegenStrategy.cpp - Linalg programmable codegen strategy ---------===//
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 logic and helpers to expose Linalg transforms as
10 // composable rewrite patterns through a programmable CodegenStrategy object.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "mlir/Dialect/Linalg/Transforms/CodegenStrategy.h"
15 
16 #include "mlir/Dialect/Linalg/Transforms/Hoisting.h"
17 #include "mlir/Dialect/Vector/VectorOps.h"
18 #include "mlir/Dialect/Vector/VectorTransforms.h"
19 #include "mlir/Pass/PassManager.h"
20 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
21 #include "mlir/Transforms/LoopUtils.h"
22 #include "mlir/Transforms/Passes.h"
23 
24 using namespace mlir;
25 using namespace mlir::linalg;
26 
27 #define DEBUG_TYPE "linalg-codegen-strategy"
28 
29 void mlir::linalg::CodegenStrategy::transform(FuncOp func) const {
30   MLIRContext *context = func.getContext();
31   // Emplace patterns one at a time while also maintaining a simple chained
32   // state transition.
33   unsigned stepCount = 0;
34   SmallVector<FrozenRewritePatternSet, 4> stage1Patterns;
35   auto zeroState = Identifier::get(std::to_string(stepCount), context);
36   auto currentState = zeroState;
37   for (const std::unique_ptr<Transformation> &t : transformationSequence) {
38     auto nextState = Identifier::get(std::to_string(++stepCount), context);
39     auto marker = (currentState == zeroState)
40                       ? linalg::LinalgTransformationFilter(
41                             t->filter, ArrayRef<Identifier>{}, nextState)
42                       : linalg::LinalgTransformationFilter(
43                             t->filter, currentState, nextState);
44     stage1Patterns.emplace_back(t->buildRewritePatterns(context, marker));
45     currentState = nextState;
46   }
47 
48   RewritePatternSet stage2Patterns =
49       linalg::getLinalgTilingCanonicalizationPatterns(context);
50   stage2Patterns.add<AffineMinSCFCanonicalizationPattern>(context);
51 
52   auto stage3Transforms = [&](Operation *op) {
53     // Some of these may be too aggressive as a stage 3 that is applied on each
54     // stage 1 application and may have to be split out to post staged patterns
55     // application (in which case they could just be passes, TBD).
56     if (lateCodegenStrategyOptions.enableLICM) {
57       op->walk([&](LoopLikeOpInterface loopLike) {
58         LLVM_DEBUG(loopLike.print(llvm::dbgs() << "\nOriginal loop:\n"));
59         if (failed(moveLoopInvariantCode(loopLike)))
60           llvm_unreachable("unexpected LICM failure");
61       });
62     }
63     promoteSingleIterationLoops(cast<FuncOp>(op));
64     if (lateCodegenStrategyOptions.enableHoistRedundantVectorTransfers)
65       hoistRedundantVectorTransfers(cast<FuncOp>(op));
66     if (lateCodegenStrategyOptions.enableHoistRedundantVectorTransfersOnTensor)
67       hoistRedundantVectorTransfersOnTensor(cast<FuncOp>(op));
68     return success();
69   };
70   (void)linalg::applyStagedPatterns(
71       func, stage1Patterns, std::move(stage2Patterns), stage3Transforms);
72 
73   //===--------------------------------------------------------------------===//
74   // Post staged patterns transforms
75   //===--------------------------------------------------------------------===//
76 
77   // Programmatic splitting of slow/fast path vector transfers.
78   if (lateCodegenStrategyOptions.enableVectorTransferPartialRewrite) {
79     RewritePatternSet patterns(context);
80     patterns.add<vector::VectorTransferFullPartialRewriter>(
81         context, vectorTransformsOptions);
82     (void)applyPatternsAndFoldGreedily(func, std::move(patterns));
83   }
84 
85   // Programmatic controlled lowering of vector.contract only.
86   if (lateCodegenStrategyOptions.enableVectorContractLowering) {
87     RewritePatternSet vectorContractLoweringPatterns(context);
88     vectorContractLoweringPatterns
89         .add<ContractionOpToOuterProductOpLowering,
90              ContractionOpToMatmulOpLowering, ContractionOpLowering>(
91             vectorTransformsOptions, context);
92     (void)applyPatternsAndFoldGreedily(
93         func, std::move(vectorContractLoweringPatterns));
94   }
95 
96   // Programmatic controlled lowering of vector.transfer only.
97   if (lateCodegenStrategyOptions.enableVectorToSCFConversion) {
98     RewritePatternSet vectorToLoopsPatterns(context);
99     populateVectorToSCFConversionPatterns(vectorToLoopsPatterns,
100                                           vectorToSCFOptions);
101     (void)applyPatternsAndFoldGreedily(func, std::move(vectorToLoopsPatterns));
102   }
103 
104   // Ensure we drop the marker in the end.
105   func.walk([](LinalgOp op) {
106     op->removeAttr(LinalgTransforms::kLinalgTransformMarker);
107   });
108 }
109