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       1             : //===- llvm/Analysis/LegacyDivergenceAnalysis.h - KernelDivergence 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 kernel divergence analysis is an LLVM pass which can be used to find out
      11             : // if a branch instruction in a GPU program (kernel) 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             : #ifndef LLVM_ANALYSIS_LEGACY_DIVERGENCE_ANALYSIS_H
      17             : #define LLVM_ANALYSIS_LEGACY_DIVERGENCE_ANALYSIS_H
      18             : 
      19             : #include "llvm/ADT/DenseSet.h"
      20             : #include "llvm/IR/Function.h"
      21             : #include "llvm/Pass.h"
      22             : 
      23             : namespace llvm {
      24             : class Value;
      25             : class LegacyDivergenceAnalysis : public FunctionPass {
      26             : public:
      27             :   static char ID;
      28             : 
      29       20286 :   LegacyDivergenceAnalysis() : FunctionPass(ID) {
      30       10143 :     initializeLegacyDivergenceAnalysisPass(*PassRegistry::getPassRegistry());
      31       10143 :   }
      32             : 
      33             :   void getAnalysisUsage(AnalysisUsage &AU) const override;
      34             : 
      35             :   bool runOnFunction(Function &F) override;
      36             : 
      37             :   // Print all divergent branches in the function.
      38             :   void print(raw_ostream &OS, const Module *) const override;
      39             : 
      40             :   // Returns true if V is divergent at its definition.
      41             :   //
      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); }
      45             : 
      46             :   // Returns true if V is uniform/non-divergent.
      47             :   //
      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); }
      51             : 
      52             :   // Keep the analysis results uptodate by removing an erased value.
      53             :   void removeValue(const Value *V) { DivergentValues.erase(V); }
      54             : 
      55             : private:
      56             :   // Stores all divergent values.
      57             :   DenseSet<const Value *> DivergentValues;
      58             : };
      59             : } // End llvm namespace
      60             : 
      61             : #endif //LLVM_ANALYSIS_LEGACY_DIVERGENCE_ANALYSIS_H