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98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
//===- TestConstantFold.cpp - Pass to test constant folding ---------------===//
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//
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// Copyright 2019 The MLIR Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// =============================================================================
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#include "mlir/AffineOps/AffineOps.h"
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#include "mlir/IR/Builders.h"
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#include "mlir/IR/Function.h"
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#include "mlir/Pass/Pass.h"
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#include "mlir/StandardOps/Ops.h"
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#include "mlir/Transforms/ConstantFoldUtils.h"
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#include "mlir/Transforms/Passes.h"
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#include "mlir/Transforms/Utils.h"
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using namespace mlir;
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namespace {
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/// Simple constant folding pass.
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struct TestConstantFold : public FunctionPass<TestConstantFold> {
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// All constants in the function post folding.
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SmallVector<Operation *, 8> existingConstants;
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// Operations that were folded and that need to be erased.
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std::vector<Operation *> opsToErase;
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void foldOperation(Operation *op, ConstantFoldHelper &helper);
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void runOnFunction() override;
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};
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} // end anonymous namespace
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void TestConstantFold::foldOperation(Operation *op,
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ConstantFoldHelper &helper) {
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// Attempt to fold the specified operation, including handling unused or
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// duplicated constants.
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if (helper.tryToConstantFold(op)) {
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opsToErase.push_back(op);
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}
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// If this op is a constant that are used and cannot be de-duplicated,
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// remember it for cleanup later.
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else if (auto constant = dyn_cast<ConstantOp>(op)) {
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existingConstants.push_back(op);
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}
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}
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// For now, we do a simple top-down pass over a function folding constants. We
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// don't handle conditional control flow, block arguments, folding conditional
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// branches, or anything else fancy.
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void TestConstantFold::runOnFunction() {
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existingConstants.clear();
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opsToErase.clear();
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auto &f = getFunction();
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ConstantFoldHelper helper(&f);
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// Collect and fold the operations within the function.
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SmallVector<Operation *, 8> ops;
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f.walk([&](Operation *op) { ops.push_back(op); });
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// Fold the constants in reverse so that the last generated constants from
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// folding are at the beginning. This creates somewhat of a linear ordering to
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// the newly generated constants that matches the operation order and improves
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// the readability of test cases.
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for (Operation *op : llvm::reverse(ops))
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foldOperation(op, helper);
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// At this point, these operations are dead, remove them.
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for (auto *op : opsToErase) {
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assert(op->hasNoSideEffect() && "Constant folded op with side effects?");
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op->erase();
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}
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// By the time we are done, we may have simplified a bunch of code, leaving
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// around dead constants. Check for them now and remove them.
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for (auto *cst : existingConstants) {
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if (cst->use_empty())
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cst->erase();
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}
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}
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/// Creates a constant folding pass.
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FunctionPassBase *mlir::createTestConstantFoldPass() {
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return new TestConstantFold();
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}
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static PassRegistration<TestConstantFold>
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pass("test-constant-fold", "Test operation constant folding");
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