Index: include/llvm/Analysis/DivergenceAnalysis.h =================================================================== --- /dev/null +++ include/llvm/Analysis/DivergenceAnalysis.h @@ -0,0 +1,48 @@ +//===- 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. +// +//===----------------------------------------------------------------------===// + +#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. + bool isDivergent(const Value *V) const { return DivergentValues.count(V); } + + // Returns true if V is uniform/non-divergent. + bool isUniform(const Value *V) const { return !isDivergent(V); } + +private: + // Stores all divergent values. + DenseSet DivergentValues; +}; +} // End llvm namespace Index: lib/Analysis/DivergenceAnalysis.cpp =================================================================== --- lib/Analysis/DivergenceAnalysis.cpp +++ lib/Analysis/DivergenceAnalysis.cpp @@ -1,4 +1,4 @@ -//===- DivergenceAnalysis.cpp ------ Divergence Analysis ------------------===// +//===- DivergenceAnalysis.cpp --------- Divergence Analysis Implementation -==// // // The LLVM Compiler Infrastructure // @@ -7,8 +7,8 @@ // //===----------------------------------------------------------------------===// // -// This file defines divergence analysis which determines whether a branch in a -// GPU program is divergent. It can help branch optimizations such as jump +// This file implements divergence analysis which determines whether a branch +// in a GPU program is divergent.It can help branch optimizations such as jump // threading and loop unswitching to make better decisions. // // GPU programs typically use the SIMD execution model, where multiple threads @@ -61,75 +61,31 @@ // 2. memory as black box. It conservatively considers values loaded from // generic or local address as divergent. This can be improved by leveraging // pointer analysis. +// //===----------------------------------------------------------------------===// -#include -#include "llvm/IR/Dominators.h" -#include "llvm/ADT/DenseSet.h" +#include "llvm/Analysis/DivergenceAnalysis.h" #include "llvm/Analysis/Passes.h" #include "llvm/Analysis/PostDominators.h" #include "llvm/Analysis/TargetTransformInfo.h" -#include "llvm/IR/Function.h" +#include "llvm/IR/Dominators.h" #include "llvm/IR/InstIterator.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/Value.h" -#include "llvm/Pass.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Transforms/Scalar.h" +#include using namespace llvm; -#define DEBUG_TYPE "divergence" - -namespace { -class DivergenceAnalysis : public FunctionPass { -public: - static char ID; - - DivergenceAnalysis() : FunctionPass(ID) { - initializeDivergenceAnalysisPass(*PassRegistry::getPassRegistry()); - } - - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addRequired(); - AU.addRequired(); - AU.setPreservesAll(); - } - - 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. - bool isDivergent(const Value *V) const { return DivergentValues.count(V); } - // Returns true if V is uniform/non-divergent. - bool isUniform(const Value *V) const { return !isDivergent(V); } - -private: - // Stores all divergent values. - DenseSet DivergentValues; -}; -} // End of anonymous namespace - -// Register this pass. -char DivergenceAnalysis::ID = 0; -INITIALIZE_PASS_BEGIN(DivergenceAnalysis, "divergence", "Divergence Analysis", - false, true) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_DEPENDENCY(PostDominatorTree) -INITIALIZE_PASS_END(DivergenceAnalysis, "divergence", "Divergence Analysis", - false, true) - namespace { class DivergencePropagator { public: - DivergencePropagator(Function &F, TargetTransformInfo &TTI, - DominatorTree &DT, PostDominatorTree &PDT, - DenseSet &DV) + DivergencePropagator(Function &F, TargetTransformInfo &TTI, DominatorTree &DT, + PostDominatorTree &PDT, DenseSet &DV) : F(F), TTI(TTI), DT(DT), PDT(PDT), DV(DV) {} void populateWithSourcesOfDivergence(); void propagate(); @@ -153,7 +109,7 @@ DominatorTree &DT; PostDominatorTree &PDT; std::vector Worklist; // Stack for DFS. - DenseSet &DV; // Stores all divergent values. + DenseSet &DV; // Stores all divergent values. }; void DivergencePropagator::populateWithSourcesOfDivergence() { @@ -286,10 +242,25 @@ } /// end namespace anonymous +// Register this pass. +char DivergenceAnalysis::ID = 0; +INITIALIZE_PASS_BEGIN(DivergenceAnalysis, "divergence", "Divergence Analysis", + false, true) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_DEPENDENCY(PostDominatorTree) +INITIALIZE_PASS_END(DivergenceAnalysis, "divergence", "Divergence Analysis", + false, true) + FunctionPass *llvm::createDivergenceAnalysisPass() { return new DivergenceAnalysis(); } +void DivergenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired(); + AU.addRequired(); + AU.setPreservesAll(); +} + bool DivergenceAnalysis::runOnFunction(Function &F) { auto *TTIWP = getAnalysisIfAvailable(); if (TTIWP == nullptr)