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//===---- Delinearization.cpp - MultiDimensional Index Delinearization ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements an analysis pass that tries to delinearize all GEP
// instructions in all loops using the SCEV analysis functionality. This pass is
// only used for testing purposes: if your pass needs delinearization, please
// use the on-demand SCEVAddRecExpr::delinearize() function.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/Constants.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Type.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DL_NAME "delinearize"
#define DEBUG_TYPE DL_NAME
namespace {
class Delinearization : public FunctionPass {
Delinearization(const Delinearization &); // do not implement
protected:
Function *F;
LoopInfo *LI;
ScalarEvolution *SE;
public:
static char ID; // Pass identification, replacement for typeid
Delinearization() : FunctionPass(ID) {
initializeDelinearizationPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
void print(raw_ostream &O, const Module *M = nullptr) const override;
};
} // end anonymous namespace
void Delinearization::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<LoopInfo>();
AU.addRequired<ScalarEvolution>();
}
bool Delinearization::runOnFunction(Function &F) {
this->F = &F;
SE = &getAnalysis<ScalarEvolution>();
LI = &getAnalysis<LoopInfo>();
return false;
}
static Value *getPointerOperand(Instruction &Inst) {
if (LoadInst *Load = dyn_cast<LoadInst>(&Inst))
return Load->getPointerOperand();
else if (StoreInst *Store = dyn_cast<StoreInst>(&Inst))
return Store->getPointerOperand();
else if (GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(&Inst))
return Gep->getPointerOperand();
return nullptr;
}
void Delinearization::print(raw_ostream &O, const Module *) const {
O << "Delinearization on function " << F->getName() << ":\n";
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
Instruction *Inst = &(*I);
// Only analyze loads and stores.
if (!isa<StoreInst>(Inst) && !isa<LoadInst>(Inst) &&
!isa<GetElementPtrInst>(Inst))
continue;
const BasicBlock *BB = Inst->getParent();
// Delinearize the memory access as analyzed in all the surrounding loops.
// Do not analyze memory accesses outside loops.
for (Loop *L = LI->getLoopFor(BB); L != nullptr; L = L->getParentLoop()) {
const SCEV *AccessFn = SE->getSCEVAtScope(getPointerOperand(*Inst), L);
const SCEVUnknown *BasePointer =
dyn_cast<SCEVUnknown>(SE->getPointerBase(AccessFn));
// Do not delinearize if we cannot find the base pointer.
if (!BasePointer)
break;
AccessFn = SE->getMinusSCEV(AccessFn, BasePointer);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(AccessFn);
// Do not try to delinearize memory accesses that are not AddRecs.
if (!AR)
break;
O << "\n";
O << "Inst:" << *Inst << "\n";
O << "In Loop with Header: " << L->getHeader()->getName() << "\n";
O << "AddRec: " << *AR << "\n";
SmallVector<const SCEV *, 3> Subscripts, Sizes;
AR->delinearize(*SE, Subscripts, Sizes, SE->getElementSize(Inst));
if (Subscripts.size() == 0 || Sizes.size() == 0 ||
Subscripts.size() != Sizes.size()) {
O << "failed to delinearize\n";
continue;
}
O << "Base offset: " << *BasePointer << "\n";
O << "ArrayDecl[UnknownSize]";
int Size = Subscripts.size();
for (int i = 0; i < Size - 1; i++)
O << "[" << *Sizes[i] << "]";
O << " with elements of " << *Sizes[Size - 1] << " bytes.\n";
O << "ArrayRef";
for (int i = 0; i < Size; i++)
O << "[" << *Subscripts[i] << "]";
O << "\n";
}
}
}
char Delinearization::ID = 0;
static const char delinearization_name[] = "Delinearization";
INITIALIZE_PASS_BEGIN(Delinearization, DL_NAME, delinearization_name, true,
true)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_END(Delinearization, DL_NAME, delinearization_name, true, true)
FunctionPass *llvm::createDelinearizationPass() { return new Delinearization; }
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