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
17     : public PassWrapper<TestConstantFold, OperationPass<>> {
18   MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TestConstantFold)
19 
20   StringRef getArgument() const final { return "test-constant-fold"; }
21   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 };
30 } // namespace
31 
32 void TestConstantFold::foldOperation(Operation *op, OperationFolder &helper) {
33   auto processGeneratedConstants = [this](Operation *op) {
34     existingConstants.push_back(op);
35   };
36 
37   // Attempt to fold the specified operation, including handling unused or
38   // duplicated constants.
39   (void)helper.tryToFold(op, processGeneratedConstants);
40 }
41 
42 void TestConstantFold::runOnOperation() {
43   existingConstants.clear();
44 
45   // Collect and fold the operations within the operation.
46   SmallVector<Operation *, 8> ops;
47   getOperation()->walk([&](Operation *op) { ops.push_back(op); });
48 
49   // Fold the constants in reverse so that the last generated constants from
50   // folding are at the beginning. This creates somewhat of a linear ordering to
51   // the newly generated constants that matches the operation order and improves
52   // the readability of test cases.
53   OperationFolder helper(&getContext());
54   for (Operation *op : llvm::reverse(ops))
55     foldOperation(op, helper);
56 
57   // By the time we are done, we may have simplified a bunch of code, leaving
58   // around dead constants. Check for them now and remove them.
59   for (auto *cst : existingConstants) {
60     if (cst->use_empty())
61       cst->erase();
62   }
63 }
64 
65 namespace mlir {
66 namespace test {
67 void registerTestConstantFold() { PassRegistration<TestConstantFold>(); }
68 } // namespace test
69 } // namespace mlir
70