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Diffstat (limited to 'chromium/third_party/glslang/src/SPIRV/InReadableOrder.cpp')
-rw-r--r-- | chromium/third_party/glslang/src/SPIRV/InReadableOrder.cpp | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/chromium/third_party/glslang/src/SPIRV/InReadableOrder.cpp b/chromium/third_party/glslang/src/SPIRV/InReadableOrder.cpp new file mode 100644 index 00000000000..86aae6d057f --- /dev/null +++ b/chromium/third_party/glslang/src/SPIRV/InReadableOrder.cpp @@ -0,0 +1,113 @@ +// +//Copyright (C) 2016 Google, Inc. +// +//All rights reserved. +// +//Redistribution and use in source and binary forms, with or without +//modification, are permitted provided that the following conditions +//are met: +// +// Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// +// Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following +// disclaimer in the documentation and/or other materials provided +// with the distribution. +// +// Neither the name of 3Dlabs Inc. Ltd. nor the names of its +// contributors may be used to endorse or promote products derived +// from this software without specific prior written permission. +// +//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +//"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +//LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +//FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +//COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +//INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +//BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +//LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +//CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +//LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +//ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +//POSSIBILITY OF SUCH DAMAGE. + +// The SPIR-V spec requires code blocks to appear in an order satisfying the +// dominator-tree direction (ie, dominator before the dominated). This is, +// actually, easy to achieve: any pre-order CFG traversal algorithm will do it. +// Because such algorithms visit a block only after traversing some path to it +// from the root, they necessarily visit the block's idom first. +// +// But not every graph-traversal algorithm outputs blocks in an order that +// appears logical to human readers. The problem is that unrelated branches may +// be interspersed with each other, and merge blocks may come before some of the +// branches being merged. +// +// A good, human-readable order of blocks may be achieved by performing +// depth-first search but delaying merge nodes until after all their branches +// have been visited. This is implemented below by the inReadableOrder() +// function. + +#include "spvIR.h" + +#include <cassert> +#include <unordered_map> + +using spv::Block; +using spv::Id; + +namespace { +// Traverses CFG in a readable order, invoking a pre-set callback on each block. +// Use by calling visit() on the root block. +class ReadableOrderTraverser { +public: + explicit ReadableOrderTraverser(std::function<void(Block*)> callback) : callback_(callback) {} + // Visits the block if it hasn't been visited already and isn't currently + // being delayed. Invokes callback(block), then descends into its + // successors. Delays merge-block and continue-block processing until all + // the branches have been completed. + void visit(Block* block) + { + assert(block); + if (visited_[block] || delayed_[block]) + return; + callback_(block); + visited_[block] = true; + Block* mergeBlock = nullptr; + Block* continueBlock = nullptr; + auto mergeInst = block->getMergeInstruction(); + if (mergeInst) { + Id mergeId = mergeInst->getIdOperand(0); + mergeBlock = block->getParent().getParent().getInstruction(mergeId)->getBlock(); + delayed_[mergeBlock] = true; + if (mergeInst->getOpCode() == spv::OpLoopMerge) { + Id continueId = mergeInst->getIdOperand(1); + continueBlock = + block->getParent().getParent().getInstruction(continueId)->getBlock(); + delayed_[continueBlock] = true; + } + } + const auto successors = block->getSuccessors(); + for (auto it = successors.cbegin(); it != successors.cend(); ++it) + visit(*it); + if (continueBlock) { + delayed_[continueBlock] = false; + visit(continueBlock); + } + if (mergeBlock) { + delayed_[mergeBlock] = false; + visit(mergeBlock); + } + } + +private: + std::function<void(Block*)> callback_; + // Whether a block has already been visited or is being delayed. + std::unordered_map<Block *, bool> visited_, delayed_; +}; +} + +void spv::inReadableOrder(Block* root, std::function<void(Block*)> callback) +{ + ReadableOrderTraverser(callback).visit(root); +} |