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/Pass.h" 28 #include "llvm/Support/Debug.h" 29 #include "llvm/Support/raw_ostream.h" 30 31 using namespace llvm; 32 33 #define DL_NAME "delinearize" 34 #define DEBUG_TYPE DL_NAME 35 36 namespace { 37 38 class Delinearization : public FunctionPass { 39 Delinearization(const Delinearization &); // do not implement 40 protected: 41 Function *F; 42 LoopInfo *LI; 43 ScalarEvolution *SE; 44 45 public: 46 static char ID; // Pass identification, replacement for typeid 47 48 Delinearization() : FunctionPass(ID) { 49 initializeDelinearizationPass(*PassRegistry::getPassRegistry()); 50 } 51 bool runOnFunction(Function &F) override; 52 void getAnalysisUsage(AnalysisUsage &AU) const override; 53 void print(raw_ostream &O, const Module *M = nullptr) const override; 54 }; 55 56 } // end anonymous namespace 57 58 void Delinearization::getAnalysisUsage(AnalysisUsage &AU) const { 59 AU.setPreservesAll(); 60 AU.addRequired<LoopInfoWrapperPass>(); 61 AU.addRequired<ScalarEvolutionWrapperPass>(); 62 } 63 64 bool Delinearization::runOnFunction(Function &F) { 65 this->F = &F; 66 SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE(); 67 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); 68 return false; 69 } 70 71 void Delinearization::print(raw_ostream &O, const Module *) const { 72 O << "Delinearization on function " << F->getName() << ":\n"; 73 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) { 74 Instruction *Inst = &(*I); 75 76 // Only analyze loads and stores. 77 if (!isa<StoreInst>(Inst) && !isa<LoadInst>(Inst) && 78 !isa<GetElementPtrInst>(Inst)) 79 continue; 80 81 const BasicBlock *BB = Inst->getParent(); 82 // Delinearize the memory access as analyzed in all the surrounding loops. 83 // Do not analyze memory accesses outside loops. 84 for (Loop *L = LI->getLoopFor(BB); L != nullptr; L = L->getParentLoop()) { 85 const SCEV *AccessFn = SE->getSCEVAtScope(getPointerOperand(Inst), L); 86 87 const SCEVUnknown *BasePointer = 88 dyn_cast<SCEVUnknown>(SE->getPointerBase(AccessFn)); 89 // Do not delinearize if we cannot find the base pointer. 90 if (!BasePointer) 91 break; 92 AccessFn = SE->getMinusSCEV(AccessFn, BasePointer); 93 94 O << "\n"; 95 O << "Inst:" << *Inst << "\n"; 96 O << "In Loop with Header: " << L->getHeader()->getName() << "\n"; 97 O << "AccessFunction: " << *AccessFn << "\n"; 98 99 SmallVector<const SCEV *, 3> Subscripts, Sizes; 100 SE->delinearize(AccessFn, Subscripts, Sizes, SE->getElementSize(Inst)); 101 if (Subscripts.size() == 0 || Sizes.size() == 0 || 102 Subscripts.size() != Sizes.size()) { 103 O << "failed to delinearize\n"; 104 continue; 105 } 106 107 O << "Base offset: " << *BasePointer << "\n"; 108 O << "ArrayDecl[UnknownSize]"; 109 int Size = Subscripts.size(); 110 for (int i = 0; i < Size - 1; i++) 111 O << "[" << *Sizes[i] << "]"; 112 O << " with elements of " << *Sizes[Size - 1] << " bytes.\n"; 113 114 O << "ArrayRef"; 115 for (int i = 0; i < Size; i++) 116 O << "[" << *Subscripts[i] << "]"; 117 O << "\n"; 118 } 119 } 120 } 121 122 char Delinearization::ID = 0; 123 static const char delinearization_name[] = "Delinearization"; 124 INITIALIZE_PASS_BEGIN(Delinearization, DL_NAME, delinearization_name, true, 125 true) 126 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) 127 INITIALIZE_PASS_END(Delinearization, DL_NAME, delinearization_name, true, true) 128 129 FunctionPass *llvm::createDelinearizationPass() { return new Delinearization; } 130