1 //===- llvm/Analysis/DivergenceAnalysis.h - Divergence Analysis -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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
15 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H
17 #define LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H
19 #include "llvm/ADT/DenseSet.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/Pass.h"
25 class DivergenceAnalysis : public FunctionPass {
29 DivergenceAnalysis() : FunctionPass(ID) {
30 initializeDivergenceAnalysisPass(*PassRegistry::getPassRegistry());
33 void getAnalysisUsage(AnalysisUsage &AU) const override;
35 bool runOnFunction(Function &F) override;
37 // Print all divergent branches in the function.
38 void print(raw_ostream &OS, const Module *) const override;
40 // Returns true if V is divergent at its definition.
42 // Even if this function returns false, V may still be divergent when used
43 // in a different basic block.
44 bool isDivergent(const Value *V) const { return DivergentValues.count(V); }
46 // Returns true if V is uniform/non-divergent.
48 // Even if this function returns true, V may still be divergent when used
49 // in a different basic block.
50 bool isUniform(const Value *V) const { return !isDivergent(V); }
52 // Keep the analysis results uptodate by removing an erased value.
53 void removeValue(const Value *V) { DivergentValues.erase(V); }
56 // Stores all divergent values.
57 DenseSet<const Value *> DivergentValues;
59 } // End llvm namespace
61 #endif //LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H