1 //===---- Delinearization.cpp - MultiDimensional Index Delinearization ----===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This implements an analysis pass that tries to delinearize all GEP 10 // instructions in all loops using the SCEV analysis functionality. This pass is 11 // only used for testing purposes: if your pass needs delinearization, please 12 // use the on-demand SCEVAddRecExpr::delinearize() function. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/Analysis/LoopInfo.h" 17 #include "llvm/Analysis/Passes.h" 18 #include "llvm/Analysis/ScalarEvolution.h" 19 #include "llvm/Analysis/ScalarEvolutionExpressions.h" 20 #include "llvm/IR/Constants.h" 21 #include "llvm/IR/DerivedTypes.h" 22 #include "llvm/IR/Function.h" 23 #include "llvm/IR/InstIterator.h" 24 #include "llvm/IR/Instructions.h" 25 #include "llvm/IR/LLVMContext.h" 26 #include "llvm/IR/Type.h" 27 #include "llvm/InitializePasses.h" 28 #include "llvm/Pass.h" 29 #include "llvm/Support/Debug.h" 30 #include "llvm/Support/raw_ostream.h" 31 32 using namespace llvm; 33 34 #define DL_NAME "delinearize" 35 #define DEBUG_TYPE DL_NAME 36 37 namespace { 38 39 class Delinearization : public FunctionPass { 40 Delinearization(const Delinearization &); // do not implement 41 protected: 42 Function *F; 43 LoopInfo *LI; 44 ScalarEvolution *SE; 45 46 public: 47 static char ID; // Pass identification, replacement for typeid 48 49 Delinearization() : FunctionPass(ID) { 50 initializeDelinearizationPass(*PassRegistry::getPassRegistry()); 51 } 52 bool runOnFunction(Function &F) override; 53 void getAnalysisUsage(AnalysisUsage &AU) const override; 54 void print(raw_ostream &O, const Module *M = nullptr) const override; 55 }; 56 57 } // end anonymous namespace 58 59 void Delinearization::getAnalysisUsage(AnalysisUsage &AU) const { 60 AU.setPreservesAll(); 61 AU.addRequired<LoopInfoWrapperPass>(); 62 AU.addRequired<ScalarEvolutionWrapperPass>(); 63 } 64 65 bool Delinearization::runOnFunction(Function &F) { 66 this->F = &F; 67 SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE(); 68 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); 69 return false; 70 } 71 72 void Delinearization::print(raw_ostream &O, const Module *) const { 73 O << "Delinearization on function " << F->getName() << ":\n"; 74 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) { 75 Instruction *Inst = &(*I); 76 77 // Only analyze loads and stores. 78 if (!isa<StoreInst>(Inst) && !isa<LoadInst>(Inst) && 79 !isa<GetElementPtrInst>(Inst)) 80 continue; 81 82 const BasicBlock *BB = Inst->getParent(); 83 // Delinearize the memory access as analyzed in all the surrounding loops. 84 // Do not analyze memory accesses outside loops. 85 for (Loop *L = LI->getLoopFor(BB); L != nullptr; L = L->getParentLoop()) { 86 const SCEV *AccessFn = SE->getSCEVAtScope(getPointerOperand(Inst), L); 87 88 const SCEVUnknown *BasePointer = 89 dyn_cast<SCEVUnknown>(SE->getPointerBase(AccessFn)); 90 // Do not delinearize if we cannot find the base pointer. 91 if (!BasePointer) 92 break; 93 AccessFn = SE->getMinusSCEV(AccessFn, BasePointer); 94 95 O << "\n"; 96 O << "Inst:" << *Inst << "\n"; 97 O << "In Loop with Header: " << L->getHeader()->getName() << "\n"; 98 O << "AccessFunction: " << *AccessFn << "\n"; 99 100 SmallVector<const SCEV *, 3> Subscripts, Sizes; 101 SE->delinearize(AccessFn, Subscripts, Sizes, SE->getElementSize(Inst)); 102 if (Subscripts.size() == 0 || Sizes.size() == 0 || 103 Subscripts.size() != Sizes.size()) { 104 O << "failed to delinearize\n"; 105 continue; 106 } 107 108 O << "Base offset: " << *BasePointer << "\n"; 109 O << "ArrayDecl[UnknownSize]"; 110 int Size = Subscripts.size(); 111 for (int i = 0; i < Size - 1; i++) 112 O << "[" << *Sizes[i] << "]"; 113 O << " with elements of " << *Sizes[Size - 1] << " bytes.\n"; 114 115 O << "ArrayRef"; 116 for (int i = 0; i < Size; i++) 117 O << "[" << *Subscripts[i] << "]"; 118 O << "\n"; 119 } 120 } 121 } 122 123 char Delinearization::ID = 0; 124 static const char delinearization_name[] = "Delinearization"; 125 INITIALIZE_PASS_BEGIN(Delinearization, DL_NAME, delinearization_name, true, 126 true) 127 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) 128 INITIALIZE_PASS_END(Delinearization, DL_NAME, delinearization_name, true, true) 129 130 FunctionPass *llvm::createDelinearizationPass() { return new Delinearization; } 131