1//===- llvm/Analysis/LegacyDivergenceAnalysis.h - KernelDivergence Analysis -*- C++ -*-===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// The kernel divergence analysis is an LLVM pass which can be used to find out 10// if a branch instruction in a GPU program (kernel) is divergent or not. It can help 11// branch optimizations such as jump threading and loop unswitching to make 12// better decisions. 13// 14//===----------------------------------------------------------------------===// 15#ifndef LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H 16#define LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H 17 18#include "llvm/ADT/DenseSet.h" 19#include "llvm/Pass.h" 20#include <memory> 21 22namespace llvm { 23class DivergenceInfo; 24class Function; 25class Module; 26class raw_ostream; 27class TargetTransformInfo; 28class Use; 29class Value; 30 31class LegacyDivergenceAnalysis : public FunctionPass { 32public: 33 static char ID; 34 35 LegacyDivergenceAnalysis(); 36 37 void getAnalysisUsage(AnalysisUsage &AU) const override; 38 39 bool runOnFunction(Function &F) override; 40 41 // Print all divergent branches in the function. 42 void print(raw_ostream &OS, const Module *) const override; 43 44 // Returns true if V is divergent at its definition. 45 bool isDivergent(const Value *V) const; 46 47 // Returns true if U is divergent. Uses of a uniform value can be divergent. 48 bool isDivergentUse(const Use *U) const; 49 50 // Returns true if V is uniform/non-divergent. 51 bool isUniform(const Value *V) const { return !isDivergent(V); } 52 53 // Returns true if U is uniform/non-divergent. Uses of a uniform value can be 54 // divergent. 55 bool isUniformUse(const Use *U) const { return !isDivergentUse(U); } 56 57 // Keep the analysis results uptodate by removing an erased value. 58 void removeValue(const Value *V) { DivergentValues.erase(V); } 59 60private: 61 // Whether analysis should be performed by GPUDivergenceAnalysis. 62 bool shouldUseGPUDivergenceAnalysis(const Function &F, 63 const TargetTransformInfo &TTI) const; 64 65 // (optional) handle to new DivergenceAnalysis 66 std::unique_ptr<DivergenceInfo> gpuDA; 67 68 // Stores all divergent values. 69 DenseSet<const Value *> DivergentValues; 70 71 // Stores divergent uses of possibly uniform values. 72 DenseSet<const Use *> DivergentUses; 73}; 74} // End llvm namespace 75 76#endif // LLVM_ANALYSIS_LEGACYDIVERGENCEANALYSIS_H 77