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To compute the dimensions of the array in a unique way, we split the delinearization analysis in three steps: - find parametric terms in all memory access functions - compute the array dimensions from the set of terms - compute the delinearized access functions for each dimension The first step is executed on all the memory access functions such that we gather all the patterns in which an array is accessed. The second step reduces all this information in a unique description of the sizes of the array. The third step is delinearizing each memory access function following the common description of the shape of the array computed in step 2. This rewrite of the delinearization pass also solves a problem we had with the previous implementation: because the previous algorithm was by induction on the structure of the SCEV, it would not correctly recognize the shape of the array when the memory access was not following the nesting of the loops: for example, see polly/test/ScopInfo/multidim_only_ivs_3d_reverse.ll ; void foo(long n, long m, long o, double A[n][m][o]) { ; ; for (long i = 0; i < n; i++) ; for (long j = 0; j < m; j++) ; for (long k = 0; k < o; k++) ; A[i][k][j] = 1.0; Starting with this patch we no longer delinearize access functions that do not contain parameters, for example in test/Analysis/DependenceAnalysis/GCD.ll ;; for (long int i = 0; i < 100; i++) ;; for (long int j = 0; j < 100; j++) { ;; A[2*i - 4*j] = i; ;; *B++ = A[6*i + 8*j]; these accesses will not be delinearized as the upper bound of the loops are constants, and their access functions do not contain SCEVUnknown parameters. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208232 91177308-0d34-0410-b5e6-96231b3b80d8
140 lines
4.6 KiB
C++
140 lines
4.6 KiB
C++
//===---- Delinearization.cpp - MultiDimensional Index Delinearization ----===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This implements an analysis pass that tries to delinearize all GEP
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// instructions in all loops using the SCEV analysis functionality. This pass is
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// only used for testing purposes: if your pass needs delinearization, please
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// use the on-demand SCEVAddRecExpr::delinearize() function.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/IR/Constants.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Type.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DL_NAME "delinearize"
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#define DEBUG_TYPE DL_NAME
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namespace {
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class Delinearization : public FunctionPass {
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Delinearization(const Delinearization &); // do not implement
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protected:
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Function *F;
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LoopInfo *LI;
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ScalarEvolution *SE;
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public:
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static char ID; // Pass identification, replacement for typeid
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Delinearization() : FunctionPass(ID) {
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initializeDelinearizationPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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void print(raw_ostream &O, const Module *M = nullptr) const override;
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};
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} // end anonymous namespace
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void Delinearization::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequired<LoopInfo>();
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AU.addRequired<ScalarEvolution>();
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}
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bool Delinearization::runOnFunction(Function &F) {
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this->F = &F;
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SE = &getAnalysis<ScalarEvolution>();
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LI = &getAnalysis<LoopInfo>();
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return false;
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}
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static Value *getPointerOperand(Instruction &Inst) {
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if (LoadInst *Load = dyn_cast<LoadInst>(&Inst))
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return Load->getPointerOperand();
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else if (StoreInst *Store = dyn_cast<StoreInst>(&Inst))
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return Store->getPointerOperand();
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else if (GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(&Inst))
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return Gep->getPointerOperand();
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return nullptr;
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}
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void Delinearization::print(raw_ostream &O, const Module *) const {
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O << "Delinearization on function " << F->getName() << ":\n";
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for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
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Instruction *Inst = &(*I);
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// Only analyze loads and stores.
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if (!isa<StoreInst>(Inst) && !isa<LoadInst>(Inst) &&
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!isa<GetElementPtrInst>(Inst))
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continue;
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const BasicBlock *BB = Inst->getParent();
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// Delinearize the memory access as analyzed in all the surrounding loops.
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// Do not analyze memory accesses outside loops.
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for (Loop *L = LI->getLoopFor(BB); L != nullptr; L = L->getParentLoop()) {
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const SCEV *AccessFn = SE->getSCEVAtScope(getPointerOperand(*Inst), L);
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const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(AccessFn);
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// Do not try to delinearize memory accesses that are not AddRecs.
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if (!AR)
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break;
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O << "\n";
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O << "Inst:" << *Inst << "\n";
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O << "In Loop with Header: " << L->getHeader()->getName() << "\n";
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O << "AddRec: " << *AR << "\n";
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SmallVector<const SCEV *, 3> Subscripts, Sizes;
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const SCEV *Res = AR->delinearize(*SE, Subscripts, Sizes);
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if (Res == AR || Subscripts.size() == 0 || Sizes.size() == 0 ||
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Subscripts.size() != Sizes.size()) {
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O << "failed to delinearize\n";
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continue;
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}
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O << "Base offset: " << *Res << "\n";
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O << "ArrayDecl[UnknownSize]";
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int Size = Subscripts.size();
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for (int i = 0; i < Size - 1; i++)
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O << "[" << *Sizes[i] << "]";
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O << " with elements of " << *Sizes[Size - 1] << " bytes.\n";
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O << "ArrayRef";
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for (int i = 0; i < Size; i++)
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O << "[" << *Subscripts[i] << "]";
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O << "\n";
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}
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}
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}
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char Delinearization::ID = 0;
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static const char delinearization_name[] = "Delinearization";
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INITIALIZE_PASS_BEGIN(Delinearization, DL_NAME, delinearization_name, true,
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true)
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INITIALIZE_PASS_DEPENDENCY(LoopInfo)
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INITIALIZE_PASS_END(Delinearization, DL_NAME, delinearization_name, true, true)
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FunctionPass *llvm::createDelinearizationPass() { return new Delinearization; }
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