| //===- llvm/Analysis/LegacyDivergenceAnalysis.h - KernelDivergence Analysis -*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // The kernel divergence analysis is an LLVM pass which can be used to find out |
| // if a branch instruction in a GPU program (kernel) is divergent or not. It can help |
| // branch optimizations such as jump threading and loop unswitching to make |
| // better decisions. |
| // |
| //===----------------------------------------------------------------------===// |
| #ifndef LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H |
| #define LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H |
| |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/Pass.h" |
| #include <memory> |
| |
| namespace llvm { |
| class DivergenceInfo; |
| class Function; |
| class Module; |
| class raw_ostream; |
| class TargetTransformInfo; |
| class Use; |
| class Value; |
| |
| class LegacyDivergenceAnalysis : public FunctionPass { |
| public: |
| static char ID; |
| |
| LegacyDivergenceAnalysis(); |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override; |
| |
| bool runOnFunction(Function &F) override; |
| |
| // Print all divergent branches in the function. |
| void print(raw_ostream &OS, const Module *) const override; |
| |
| // Returns true if V is divergent at its definition. |
| bool isDivergent(const Value *V) const; |
| |
| // Returns true if U is divergent. Uses of a uniform value can be divergent. |
| bool isDivergentUse(const Use *U) const; |
| |
| // Returns true if V is uniform/non-divergent. |
| bool isUniform(const Value *V) const { return !isDivergent(V); } |
| |
| // Returns true if U is uniform/non-divergent. Uses of a uniform value can be |
| // divergent. |
| bool isUniformUse(const Use *U) const { return !isDivergentUse(U); } |
| |
| // Keep the analysis results uptodate by removing an erased value. |
| void removeValue(const Value *V) { DivergentValues.erase(V); } |
| |
| private: |
| // Whether analysis should be performed by GPUDivergenceAnalysis. |
| bool shouldUseGPUDivergenceAnalysis(const Function &F, |
| const TargetTransformInfo &TTI) const; |
| |
| // (optional) handle to new DivergenceAnalysis |
| std::unique_ptr<DivergenceInfo> gpuDA; |
| |
| // Stores all divergent values. |
| DenseSet<const Value *> DivergentValues; |
| |
| // Stores divergent uses of possibly uniform values. |
| DenseSet<const Use *> DivergentUses; |
| }; |
| } // End llvm namespace |
| |
| #endif // LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H |