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https://github.com/KhronosGroup/SPIRV-Tools
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27238bcca0
The performance of the fuzzer was unacceptable in the 'permute blocks' transformation, due to dominator analysis being repeatedly invalidated and recomputed. This change preserves the dominator analysis, together with the CFG analysis, when a block is moved down.
110 lines
4.2 KiB
C++
110 lines
4.2 KiB
C++
// Copyright (c) 2019 Google LLC
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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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#include "source/fuzz/transformation_move_block_down.h"
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#include "source/opt/basic_block.h"
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namespace spvtools {
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namespace fuzz {
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TransformationMoveBlockDown::TransformationMoveBlockDown(
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const spvtools::fuzz::protobufs::TransformationMoveBlockDown& message)
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: message_(message) {}
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TransformationMoveBlockDown::TransformationMoveBlockDown(uint32_t id) {
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message_.set_block_id(id);
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}
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bool TransformationMoveBlockDown::IsApplicable(
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opt::IRContext* context, const FactManager& /*unused*/) const {
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// Go through every block in every function, looking for a block whose id
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// matches that of the block we want to consider moving down.
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for (auto& function : *context->module()) {
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for (auto block_it = function.begin(); block_it != function.end();
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++block_it) {
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if (block_it->id() == message_.block_id()) {
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// We have found a match.
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if (block_it == function.begin()) {
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// The block is the first one appearing in the function. We are not
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// allowed to move this block down.
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return false;
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}
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// Record the block we would like to consider moving down.
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opt::BasicBlock* block_matching_id = &*block_it;
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if (!context->GetDominatorAnalysis(&function)->IsReachable(
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block_matching_id)) {
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// The block is not reachable. We are not allowed to move it down.
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return false;
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}
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// Now see whether there is some block following that block in program
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// order.
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++block_it;
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if (block_it == function.end()) {
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// There is no such block; i.e., the block we are considering moving
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// is the last one in the function. The transformation thus does not
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// apply.
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return false;
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}
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opt::BasicBlock* next_block_in_program_order = &*block_it;
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// We can move the block of interest down if and only if it does not
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// dominate the block that comes next.
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return !context->GetDominatorAnalysis(&function)->Dominates(
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block_matching_id, next_block_in_program_order);
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}
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}
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}
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// We did not find a matching block, so the transformation is not applicable:
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// there is no relevant block to move.
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return false;
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}
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void TransformationMoveBlockDown::Apply(opt::IRContext* context,
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FactManager* /*unused*/) const {
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// Go through every block in every function, looking for a block whose id
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// matches that of the block we want to move down.
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for (auto& function : *context->module()) {
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for (auto block_it = function.begin(); block_it != function.end();
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++block_it) {
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if (block_it->id() == message_.block_id()) {
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++block_it;
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assert(block_it != function.end() &&
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"To be able to move a block down, it needs to have a "
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"program-order successor.");
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function.MoveBasicBlockToAfter(message_.block_id(), &*block_it);
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// For performance, it is vital to keep the dominator analysis valid
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// (which due to https://github.com/KhronosGroup/SPIRV-Tools/issues/2889
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// requires keeping the CFG analysis valid).
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context->InvalidateAnalysesExceptFor(
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opt::IRContext::Analysis::kAnalysisDefUse |
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opt::IRContext::Analysis::kAnalysisCFG |
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opt::IRContext::Analysis::kAnalysisDominatorAnalysis);
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return;
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}
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}
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}
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assert(false && "No block was found to move down.");
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}
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protobufs::Transformation TransformationMoveBlockDown::ToMessage() const {
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protobufs::Transformation result;
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*result.mutable_move_block_down() = message_;
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return result;
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}
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} // namespace fuzz
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} // namespace spvtools
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