| // Copyright (c) 2020 Vasyl Teliman |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #ifndef SOURCE_FUZZ_TRANSFORMATION_PROPAGATE_INSTRUCTION_DOWN_H_ |
| #define SOURCE_FUZZ_TRANSFORMATION_PROPAGATE_INSTRUCTION_DOWN_H_ |
| |
| #include <map> |
| |
| #include "source/fuzz/protobufs/spirvfuzz_protobufs.h" |
| #include "source/fuzz/transformation.h" |
| #include "source/fuzz/transformation_context.h" |
| #include "source/opt/ir_context.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| class TransformationPropagateInstructionDown : public Transformation { |
| public: |
| explicit TransformationPropagateInstructionDown( |
| const protobufs::TransformationPropagateInstructionDown& message); |
| |
| TransformationPropagateInstructionDown( |
| uint32_t block_id, uint32_t phi_fresh_id, |
| const std::map<uint32_t, uint32_t>& successor_id_to_fresh_id); |
| |
| // - It should be possible to apply this transformation to |block_id| (see |
| // IsApplicableToBlock method). |
| // - Every acceptable successor of |block_id| (see GetAcceptableSuccessors |
| // method) must have an entry in the |successor_id_to_fresh_id| map unless |
| // overflow ids are available. |
| // - All values in |successor_id_to_fresh_id| and |phi_fresh_id| must be |
| // unique and fresh. |
| bool IsApplicable( |
| opt::IRContext* ir_context, |
| const TransformationContext& transformation_context) const override; |
| |
| // - Adds a clone of the propagated instruction into every acceptable |
| // successor of |block_id|. |
| // - Removes the original instruction. |
| // - Creates an OpPhi instruction if possible, that tries to group created |
| // clones. |
| // - If the original instruction's id was irrelevant - marks created |
| // instructions as irrelevant. Otherwise, marks the created instructions as |
| // synonymous to each other if possible (i.e. skips instructions, copied |
| // into dead blocks). |
| void Apply(opt::IRContext* ir_context, |
| TransformationContext* transformation_context) const override; |
| |
| protobufs::Transformation ToMessage() const override; |
| |
| // Returns true if this transformation can be applied to the block with id |
| // |block_id|. Concretely, returns true iff: |
| // - |block_id| is a result id of some reachable basic block in the module. |
| // - the block has an instruction to propagate (see |
| // GetInstructionToPropagate method). |
| // - the block has at least one acceptable successor (see |
| // GetAcceptableSuccessors method). |
| // - none of the acceptable successors have OpPhi instructions that use the |
| // original instruction. |
| // - it is possible to replace every use of the original instruction with some |
| // of the propagated instructions (or an OpPhi if we can create it - see |
| // GetOpPhiBlockId method). |
| static bool IsApplicableToBlock(opt::IRContext* ir_context, |
| uint32_t block_id); |
| |
| // Returns ids of successors of |block_id|, that can be used to propagate an |
| // instruction into. Concretely, a successor block is acceptable if all |
| // dependencies of the propagated instruction dominate it. Note that this |
| // implies that an acceptable successor must be reachable in the CFG. |
| // For example: |
| // %1 = OpLabel |
| // OpSelectionMerge %2 None |
| // OpBranchConditional %cond %2 %3 |
| // %3 = OpLabel |
| // %4 = OpUndef %int |
| // %5 = OpCopyObject %int %4 |
| // OpBranch %2 |
| // %2 = OpLabel |
| // ... |
| // In this example, %2 is not an acceptable successor of %3 since one of the |
| // dependencies (%4) of the propagated instruction (%5) does not dominate it. |
| static std::unordered_set<uint32_t> GetAcceptableSuccessors( |
| opt::IRContext* ir_context, uint32_t block_id); |
| |
| std::unordered_set<uint32_t> GetFreshIds() const override; |
| |
| private: |
| // Returns the last possible instruction in the |block_id| that satisfies the |
| // following properties: |
| // - has result id |
| // - has type id |
| // - has supported opcode (see IsOpcodeSupported method) |
| // - has no users in its basic block. |
| // Returns nullptr if no such an instruction exists. For example: |
| // %1 = OpLabel |
| // %2 = OpUndef %int |
| // %3 = OpUndef %int |
| // OpStore %var %3 |
| // OpBranch %some_block |
| // In this example: |
| // - We cannot propagate OpBranch nor OpStore since they both have unsupported |
| // opcodes and have neither result ids nor type ids. |
| // - We cannot propagate %3 either since it is used by OpStore. |
| // - We can propagate %2 since it satisfies all our conditions. |
| // The basic idea behind this method it to make sure that the returned |
| // instruction will not break domination rules in its original block when |
| // propagated. |
| static opt::Instruction* GetInstructionToPropagate(opt::IRContext* ir_context, |
| uint32_t block_id); |
| |
| // Returns true if |opcode| is supported by this transformation. |
| static bool IsOpcodeSupported(SpvOp opcode); |
| |
| // Returns the first instruction in the |block| that allows us to insert |
| // |opcode| above itself. Returns nullptr is no such instruction exists. |
| static opt::Instruction* GetFirstInsertBeforeInstruction( |
| opt::IRContext* ir_context, uint32_t block_id, SpvOp opcode); |
| |
| // Returns a result id of a basic block, where an OpPhi instruction can be |
| // inserted. Returns nullptr if it's not possible to create an OpPhi. The |
| // created OpPhi instruction groups all the propagated clones of the original |
| // instruction. |block_id| is a result id of the block we propagate the |
| // instruction from. |successor_ids| contains result ids of the successors we |
| // propagate the instruction into. Concretely, returns a non-null value if: |
| // - |block_id| is in some construct. |
| // - The merge block of that construct is reachable. |
| // - |block_id| dominates that merge block. |
| // - That merge block may not be an acceptable successor of |block_id|. |
| // - There must be at least one |block_id|'s acceptable successor for every |
| // predecessor of the merge block, dominating that predecessor. |
| // - We can't create an OpPhi if the module has neither VariablePointers nor |
| // VariablePointersStorageBuffer capabilities. |
| // A simple example of when we can insert an OpPhi instruction is: |
| // - This snippet of code: |
| // %1 = OpLabel |
| // %2 = OpUndef %int |
| // OpSelectionMerge %5 None |
| // OpBranchConditional %cond %3 %4 |
| // %3 = OpLabel |
| // OpBranch %5 |
| // %4 = OpLabel |
| // OpBranch %5 |
| // %5 = OpLabel |
| // ... |
| // will be transformed into the following one (if %2 is propagated): |
| // %1 = OpLabel |
| // OpSelectionMerge %5 None |
| // OpBranchConditional %cond %3 %4 |
| // %3 = OpLabel |
| // %6 = OpUndef %int |
| // OpBranch %5 |
| // %4 = OpLabel |
| // %7 = OpUndef %int |
| // OpBranch %5 |
| // %5 = OpLabel |
| // %8 = OpPhi %int %6 %3 %7 %4 |
| // ... |
| // The fact that we introduce an OpPhi allows us to increase the applicability |
| // of the transformation. Concretely, we wouldn't be able to apply it in the |
| // example above if %2 were used in %5. Some more complicated examples can be |
| // found in unit tests. |
| static uint32_t GetOpPhiBlockId( |
| opt::IRContext* ir_context, uint32_t block_id, |
| const opt::Instruction& inst_to_propagate, |
| const std::unordered_set<uint32_t>& successor_ids); |
| |
| protobufs::TransformationPropagateInstructionDown message_; |
| }; |
| |
| } // namespace fuzz |
| } // namespace spvtools |
| |
| #endif // SOURCE_FUZZ_TRANSFORMATION_PROPAGATE_INSTRUCTION_DOWN_H_ |