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//===- llvm/Analysis/DivergenceAnalysis.h - Divergence Analysis -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The divergence analysis is an LLVM pass which can be used to find out
// if a branch instruction in a GPU program is divergent or not. It can help
// branch optimizations such as jump threading and loop unswitching to make
// better decisions.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H
#define LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H
#include "llvm/ADT/DenseSet.h"
#include "llvm/IR/Function.h"
#include "llvm/Pass.h"
namespace llvm {
class Value;
class DivergenceAnalysis : public FunctionPass {
public:
static char ID;
DivergenceAnalysis() : FunctionPass(ID) {
initializeDivergenceAnalysisPass(*PassRegistry::getPassRegistry());
}
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.
//
// Even if this function returns false, V may still be divergent when used
// in a different basic block.
bool isDivergent(const Value *V) const { return DivergentValues.count(V); }
// Returns true if V is uniform/non-divergent.
//
// Even if this function returns true, V may still be divergent when used
// in a different basic block.
bool isUniform(const Value *V) const { return !isDivergent(V); }
// Keep the analysis results uptodate by removing an erased value.
void removeValue(const Value *V) { DivergentValues.erase(V); }
private:
// Stores all divergent values.
DenseSet<const Value *> DivergentValues;
};
} // End llvm namespace
#endif //LLVM_ANALYSIS_DIVERGENCE_ANALYSIS_H
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