1 //===- TestMemRefDependenceCheck.cpp - Test dep analysis ------------------===//
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 pass to run pair-wise memref access dependence checks.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "mlir/Dialect/Affine/Analysis/AffineAnalysis.h"
14 #include "mlir/Dialect/Affine/Analysis/AffineStructures.h"
15 #include "mlir/Dialect/Affine/Analysis/Utils.h"
16 #include "mlir/Dialect/Affine/IR/AffineOps.h"
17 #include "mlir/IR/Builders.h"
18 #include "mlir/Pass/Pass.h"
19 #include "llvm/Support/Debug.h"
20
21 #define DEBUG_TYPE "test-memref-dependence-check"
22
23 using namespace mlir;
24
25 namespace {
26
27 // TODO: Add common surrounding loop depth-wise dependence checks.
28 /// Checks dependences between all pairs of memref accesses in a Function.
29 struct TestMemRefDependenceCheck
30 : public PassWrapper<TestMemRefDependenceCheck, OperationPass<>> {
MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID__anon19e710400111::TestMemRefDependenceCheck31 MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TestMemRefDependenceCheck)
32
33 StringRef getArgument() const final { return "test-memref-dependence-check"; }
getDescription__anon19e710400111::TestMemRefDependenceCheck34 StringRef getDescription() const final {
35 return "Checks dependences between all pairs of memref accesses.";
36 }
37 SmallVector<Operation *, 4> loadsAndStores;
38 void runOnOperation() override;
39 };
40
41 } // namespace
42
43 // Returns a result string which represents the direction vector (if there was
44 // a dependence), returns the string "false" otherwise.
45 static std::string
getDirectionVectorStr(bool ret,unsigned numCommonLoops,unsigned loopNestDepth,ArrayRef<DependenceComponent> dependenceComponents)46 getDirectionVectorStr(bool ret, unsigned numCommonLoops, unsigned loopNestDepth,
47 ArrayRef<DependenceComponent> dependenceComponents) {
48 if (!ret)
49 return "false";
50 if (dependenceComponents.empty() || loopNestDepth > numCommonLoops)
51 return "true";
52 std::string result;
53 for (const auto &dependenceComponent : dependenceComponents) {
54 std::string lbStr = "-inf";
55 if (dependenceComponent.lb.has_value() &&
56 dependenceComponent.lb.value() != std::numeric_limits<int64_t>::min())
57 lbStr = std::to_string(dependenceComponent.lb.value());
58
59 std::string ubStr = "+inf";
60 if (dependenceComponent.ub.has_value() &&
61 dependenceComponent.ub.value() != std::numeric_limits<int64_t>::max())
62 ubStr = std::to_string(dependenceComponent.ub.value());
63
64 result += "[" + lbStr + ", " + ubStr + "]";
65 }
66 return result;
67 }
68
69 // For each access in 'loadsAndStores', runs a dependence check between this
70 // "source" access and all subsequent "destination" accesses in
71 // 'loadsAndStores'. Emits the result of the dependence check as a note with
72 // the source access.
checkDependences(ArrayRef<Operation * > loadsAndStores)73 static void checkDependences(ArrayRef<Operation *> loadsAndStores) {
74 for (unsigned i = 0, e = loadsAndStores.size(); i < e; ++i) {
75 auto *srcOpInst = loadsAndStores[i];
76 MemRefAccess srcAccess(srcOpInst);
77 for (unsigned j = 0; j < e; ++j) {
78 auto *dstOpInst = loadsAndStores[j];
79 MemRefAccess dstAccess(dstOpInst);
80
81 unsigned numCommonLoops =
82 getNumCommonSurroundingLoops(*srcOpInst, *dstOpInst);
83 for (unsigned d = 1; d <= numCommonLoops + 1; ++d) {
84 FlatAffineValueConstraints dependenceConstraints;
85 SmallVector<DependenceComponent, 2> dependenceComponents;
86 DependenceResult result = checkMemrefAccessDependence(
87 srcAccess, dstAccess, d, &dependenceConstraints,
88 &dependenceComponents);
89 assert(result.value != DependenceResult::Failure);
90 bool ret = hasDependence(result);
91 // TODO: Print dependence type (i.e. RAW, etc) and print
92 // distance vectors as: ([2, 3], [0, 10]). Also, shorten distance
93 // vectors from ([1, 1], [3, 3]) to (1, 3).
94 srcOpInst->emitRemark("dependence from ")
95 << i << " to " << j << " at depth " << d << " = "
96 << getDirectionVectorStr(ret, numCommonLoops, d,
97 dependenceComponents);
98 }
99 }
100 }
101 }
102
103 /// Walks the operation adding load and store ops to 'loadsAndStores'. Runs
104 /// pair-wise dependence checks.
runOnOperation()105 void TestMemRefDependenceCheck::runOnOperation() {
106 // Collect the loads and stores within the function.
107 loadsAndStores.clear();
108 getOperation()->walk([&](Operation *op) {
109 if (isa<AffineLoadOp, AffineStoreOp>(op))
110 loadsAndStores.push_back(op);
111 });
112
113 checkDependences(loadsAndStores);
114 }
115
116 namespace mlir {
117 namespace test {
registerTestMemRefDependenceCheck()118 void registerTestMemRefDependenceCheck() {
119 PassRegistration<TestMemRefDependenceCheck>();
120 }
121 } // namespace test
122 } // namespace mlir
123