1 //===- llvm/Analysis/DivergenceAnalysis.h - Divergence Analysis -*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // The divergence analysis is an LLVM pass which can be used to find out 11 // if a branch instruction in a GPU program is divergent or not. It can help 12 // branch optimizations such as jump threading and loop unswitching to make 13 // better decisions. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #include "llvm/ADT/DenseSet.h" 18 #include "llvm/IR/Function.h" 19 #include "llvm/Pass.h" 20 21 namespace llvm { 22 class Value; 23 class DivergenceAnalysis : public FunctionPass { 24 public: 25 static char ID; 26 27 DivergenceAnalysis() : FunctionPass(ID) { 28 initializeDivergenceAnalysisPass(*PassRegistry::getPassRegistry()); 29 } 30 31 void getAnalysisUsage(AnalysisUsage &AU) const override; 32 33 bool runOnFunction(Function &F) override; 34 35 // Print all divergent branches in the function. 36 void print(raw_ostream &OS, const Module *) const override; 37 38 // Returns true if V is divergent. 39 bool isDivergent(const Value *V) const { return DivergentValues.count(V); } 40 41 // Returns true if V is uniform/non-divergent. 42 bool isUniform(const Value *V) const { return !isDivergent(V); } 43 44 private: 45 // Stores all divergent values. 46 DenseSet<const Value *> DivergentValues; 47 }; 48 } // End llvm namespace 49
