1 //===---- Delinearization.cpp - MultiDimensional Index Delinearization ----===//
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 // This implements an analysis pass that tries to delinearize all GEP
11 // instructions in all loops using the SCEV analysis functionality. This pass is
12 // only used for testing purposes: if your pass needs delinearization, please
13 // use the on-demand SCEVAddRecExpr::delinearize() function.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/Analysis/Passes.h"
19 #include "llvm/Analysis/ScalarEvolution.h"
20 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/InstIterator.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/LLVMContext.h"
27 #include "llvm/IR/Type.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
Delinearization()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
getAnalysisUsage(AnalysisUsage & AU) const59 void Delinearization::getAnalysisUsage(AnalysisUsage &AU) const {
60 AU.setPreservesAll();
61 AU.addRequired<LoopInfoWrapperPass>();
62 AU.addRequired<ScalarEvolutionWrapperPass>();
63 }
64
runOnFunction(Function & F)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
print(raw_ostream & O,const Module *) const72 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";
INITIALIZE_PASS_BEGIN(Delinearization,DL_NAME,delinearization_name,true,true)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