1 //===- TestConstantFold.cpp - Pass to test constant folding ---------------===//
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 #include "mlir/Pass/Pass.h"
10 #include "mlir/Transforms/FoldUtils.h"
11
12 using namespace mlir;
13
14 namespace {
15 /// Simple constant folding pass.
16 struct TestConstantFold : public PassWrapper<TestConstantFold, OperationPass<>>,
17 public RewriterBase::Listener {
MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID__anon07a5d0d80111::TestConstantFold18 MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TestConstantFold)
19
20 StringRef getArgument() const final { return "test-constant-fold"; }
getDescription__anon07a5d0d80111::TestConstantFold21 StringRef getDescription() const final {
22 return "Test operation constant folding";
23 }
24 // All constants in the operation post folding.
25 SmallVector<Operation *> existingConstants;
26
27 void foldOperation(Operation *op, OperationFolder &helper);
28 void runOnOperation() override;
29
notifyOperationInserted__anon07a5d0d80111::TestConstantFold30 void notifyOperationInserted(Operation *op,
31 OpBuilder::InsertPoint previous) override {
32 existingConstants.push_back(op);
33 }
notifyOperationErased__anon07a5d0d80111::TestConstantFold34 void notifyOperationErased(Operation *op) override {
35 auto *it = llvm::find(existingConstants, op);
36 if (it != existingConstants.end())
37 existingConstants.erase(it);
38 }
39 };
40 } // namespace
41
foldOperation(Operation * op,OperationFolder & helper)42 void TestConstantFold::foldOperation(Operation *op, OperationFolder &helper) {
43 // Attempt to fold the specified operation, including handling unused or
44 // duplicated constants.
45 (void)helper.tryToFold(op);
46 }
47
runOnOperation()48 void TestConstantFold::runOnOperation() {
49 existingConstants.clear();
50
51 // Collect and fold the operations within the operation.
52 SmallVector<Operation *, 8> ops;
53 getOperation()->walk<mlir::WalkOrder::PreOrder>([&](Operation *op) { ops.push_back(op); });
54
55 // Fold the constants in reverse so that the last generated constants from
56 // folding are at the beginning. This creates somewhat of a linear ordering to
57 // the newly generated constants that matches the operation order and improves
58 // the readability of test cases.
59 OperationFolder helper(&getContext(), /*listener=*/this);
60 for (Operation *op : llvm::reverse(ops))
61 foldOperation(op, helper);
62
63 // By the time we are done, we may have simplified a bunch of code, leaving
64 // around dead constants. Check for them now and remove them.
65 for (auto *cst : existingConstants) {
66 if (cst->use_empty())
67 cst->erase();
68 }
69 }
70
71 namespace mlir {
72 namespace test {
registerTestConstantFold()73 void registerTestConstantFold() { PassRegistration<TestConstantFold>(); }
74 } // namespace test
75 } // namespace mlir
76