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https://github.com/KhronosGroup/SPIRV-Tools
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de7d57984d
Avoids the use of "using" in favour of explicit qualification, to be consistent with spirv-fuzz. Fixes indentation in a TODO comment. Addresses and removes two existing TODO comments by moving some helper functionality into reduction_util. Related issue: #2184.
82 lines
3.3 KiB
C++
82 lines
3.3 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/reduce/merge_blocks_reduction_opportunity.h"
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#include "source/opt/block_merge_util.h"
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#include "source/opt/ir_context.h"
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namespace spvtools {
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namespace reduce {
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MergeBlocksReductionOpportunity::MergeBlocksReductionOpportunity(
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opt::IRContext* context, opt::Function* function, opt::BasicBlock* block) {
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// Precondition: the terminator has to be OpBranch.
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assert(block->terminator()->opcode() == SpvOpBranch);
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context_ = context;
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function_ = function;
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// Get the successor block associated with the OpBranch.
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successor_block_ =
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context->cfg()->block(block->terminator()->GetSingleWordInOperand(0));
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}
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bool MergeBlocksReductionOpportunity::PreconditionHolds() {
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// Merge block opportunities can disable each other.
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// Example: Given blocks: A->B->C.
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// A is a loop header; B and C are blocks in the loop; C ends with OpReturn.
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// There are two opportunities: B and C can be merged with their predecessors.
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// Merge C. B now ends with OpReturn. We now just have: A->B.
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// Merge B is now disabled, as this would lead to A, a loop header, ending
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// with an OpReturn, which is invalid.
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const auto predecessors = context_->cfg()->preds(successor_block_->id());
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assert(1 == predecessors.size() &&
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"For a successor to be merged into its predecessor, exactly one "
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"predecessor must be present.");
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const uint32_t predecessor_id = predecessors[0];
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opt::BasicBlock* predecessor_block =
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context_->get_instr_block(predecessor_id);
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return opt::blockmergeutil::CanMergeWithSuccessor(context_,
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predecessor_block);
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}
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void MergeBlocksReductionOpportunity::Apply() {
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// While the original block that targeted the successor may not exist anymore
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// (it might have been merged with another block), some block must exist that
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// targets the successor. Find it.
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const auto predecessors = context_->cfg()->preds(successor_block_->id());
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assert(1 == predecessors.size() &&
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"For a successor to be merged into its predecessor, exactly one "
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"predecessor must be present.");
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const uint32_t predecessor_id = predecessors[0];
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// We need an iterator pointing to the predecessor, hence the loop.
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for (auto bi = function_->begin(); bi != function_->end(); ++bi) {
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if (bi->id() == predecessor_id) {
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opt::blockmergeutil::MergeWithSuccessor(context_, function_, bi);
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// Block merging changes the control flow graph, so invalidate it.
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context_->InvalidateAnalysesExceptFor(
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opt::IRContext::Analysis::kAnalysisNone);
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return;
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}
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}
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assert(false &&
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"Unreachable: we should have found a block with the desired id.");
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}
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} // namespace reduce
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} // namespace spvtools
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