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This has the side effect of reversing the order of most of IVUser's results. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112442 91177308-0d34-0410-b5e6-96231b3b80d8
271 lines
8.7 KiB
C++
271 lines
8.7 KiB
C++
//===- IVUsers.cpp - Induction Variable Users -------------------*- C++ -*-===//
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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 file implements bookkeeping for "interesting" users of expressions
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// computed from induction variables.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "iv-users"
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#include "llvm/Analysis/IVUsers.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/Type.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Assembly/AsmAnnotationWriter.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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using namespace llvm;
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char IVUsers::ID = 0;
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INITIALIZE_PASS(IVUsers, "iv-users", "Induction Variable Users", false, true);
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Pass *llvm::createIVUsersPass() {
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return new IVUsers();
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}
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/// findInterestingAddRec - Test whether the given expression is interesting.
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/// Return the addrec with the current loop which makes it interesting, or
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/// null if it is not interesting.
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const SCEVAddRecExpr *IVUsers::findInterestingAddRec(const SCEV *S) const {
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// An addrec is interesting if it's affine or if it has an interesting start.
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
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// Keep things simple. Don't touch loop-variant strides.
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if (AR->getLoop() == L)
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return AR;
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// We don't yet know how to do effective SCEV expansions for addrecs
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// with interesting steps.
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if (findInterestingAddRec(AR->getStepRecurrence(*SE)))
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return 0;
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// Otherwise recurse to see if the start value is interesting.
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return findInterestingAddRec(AR->getStart());
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}
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// An add is interesting if exactly one of its operands is interesting.
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if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
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for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
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OI != OE; ++OI)
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if (const SCEVAddRecExpr *AR = findInterestingAddRec(*OI))
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return AR;
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return 0;
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}
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// Nothing else is interesting here.
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return 0;
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}
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bool IVUsers::isInterestingUser(const Instruction *User) const {
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// Void and FP expressions cannot be reduced.
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if (!SE->isSCEVable(User->getType()))
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return false;
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// LSR is not APInt clean, do not touch integers bigger than 64-bits.
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if (SE->getTypeSizeInBits(User->getType()) > 64)
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return false;
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// Don't descend into PHI nodes outside the current loop.
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if (LI->getLoopFor(User->getParent()) != L &&
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isa<PHINode>(User))
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return false;
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// Otherwise, it may be interesting.
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return true;
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}
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/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
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/// reducible SCEV, recursively add its users to the IVUsesByStride set and
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/// return true. Otherwise, return false.
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void IVUsers::AddUsersIfInteresting(Instruction *I) {
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// Stop if we've seen this before.
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if (!Processed.insert(I))
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return;
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// If this PHI node is not SCEVable, ignore it.
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if (!SE->isSCEVable(I->getType()))
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return;
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// If this PHI node is not an addrec for this loop, ignore it.
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const SCEVAddRecExpr *Expr = findInterestingAddRec(SE->getSCEV(I));
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if (!Expr)
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return;
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// Walk the def-use graph.
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SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>, 16> Worklist;
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Worklist.push_back(std::make_pair(I, Expr));
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do {
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std::pair<Instruction *, const SCEVAddRecExpr *> P =
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Worklist.pop_back_val();
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Instruction *Op = P.first;
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const SCEVAddRecExpr *OpAR = P.second;
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// Visit Op's users.
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SmallPtrSet<Instruction *, 8> VisitedUsers;
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for (Value::use_iterator UI = Op->use_begin(), E = Op->use_end();
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UI != E; ++UI) {
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// Don't visit any individual user more than once.
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Instruction *User = cast<Instruction>(*UI);
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if (!VisitedUsers.insert(User))
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continue;
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// If it's an affine addrec (which we can pretty safely re-expand) inside
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// the loop, or a potentially non-affine addrec outside the loop (which
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// we can evaluate outside of the loop), follow it.
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if (OpAR->isAffine() || !L->contains(User)) {
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if (isInterestingUser(User)) {
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const SCEV *UserExpr = SE->getSCEV(User);
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if (const SCEVAddRecExpr *AR = findInterestingAddRec(UserExpr)) {
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// Interesting. Keep searching.
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if (Processed.insert(User))
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Worklist.push_back(std::make_pair(User, AR));
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continue;
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}
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}
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}
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// Otherwise, this is the point where the def-use chain
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// becomes uninteresting. Call it an IV User.
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AddUser(User, Op);
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}
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} while (!Worklist.empty());
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}
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IVStrideUse &IVUsers::AddUser(Instruction *User, Value *Operand) {
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IVUses.push_back(new IVStrideUse(this, User, Operand));
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IVStrideUse &NewUse = IVUses.back();
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// Auto-detect and remember post-inc loops for this expression.
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const SCEV *S = SE->getSCEV(Operand);
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(void)TransformForPostIncUse(NormalizeAutodetect,
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S, User, Operand,
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NewUse.PostIncLoops,
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*SE, *DT);
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return NewUse;
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}
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IVUsers::IVUsers()
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: LoopPass(ID) {
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}
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void IVUsers::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<LoopInfo>();
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AU.addRequired<DominatorTree>();
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AU.addRequired<ScalarEvolution>();
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AU.setPreservesAll();
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}
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bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
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L = l;
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LI = &getAnalysis<LoopInfo>();
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DT = &getAnalysis<DominatorTree>();
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SE = &getAnalysis<ScalarEvolution>();
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// Find all uses of induction variables in this loop, and categorize
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// them by stride. Start by finding all of the PHI nodes in the header for
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// this loop. If they are induction variables, inspect their uses.
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for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
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AddUsersIfInteresting(I);
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return false;
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}
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void IVUsers::print(raw_ostream &OS, const Module *M) const {
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OS << "IV Users for loop ";
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WriteAsOperand(OS, L->getHeader(), false);
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if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
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OS << " with backedge-taken count "
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<< *SE->getBackedgeTakenCount(L);
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}
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OS << ":\n";
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// Use a default AssemblyAnnotationWriter to suppress the default info
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// comments, which aren't relevant here.
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AssemblyAnnotationWriter Annotator;
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for (ilist<IVStrideUse>::const_iterator UI = IVUses.begin(),
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E = IVUses.end(); UI != E; ++UI) {
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OS << " ";
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WriteAsOperand(OS, UI->getOperandValToReplace(), false);
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OS << " = " << *getReplacementExpr(*UI);
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for (PostIncLoopSet::const_iterator
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I = UI->PostIncLoops.begin(),
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E = UI->PostIncLoops.end(); I != E; ++I) {
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OS << " (post-inc with loop ";
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WriteAsOperand(OS, (*I)->getHeader(), false);
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OS << ")";
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}
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OS << " in ";
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UI->getUser()->print(OS, &Annotator);
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OS << '\n';
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}
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}
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void IVUsers::dump() const {
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print(dbgs());
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}
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void IVUsers::releaseMemory() {
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Processed.clear();
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IVUses.clear();
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}
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/// getReplacementExpr - Return a SCEV expression which computes the
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/// value of the OperandValToReplace.
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const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &IU) const {
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return SE->getSCEV(IU.getOperandValToReplace());
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}
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/// getExpr - Return the expression for the use.
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const SCEV *IVUsers::getExpr(const IVStrideUse &IU) const {
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return
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TransformForPostIncUse(Normalize, getReplacementExpr(IU),
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IU.getUser(), IU.getOperandValToReplace(),
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const_cast<PostIncLoopSet &>(IU.getPostIncLoops()),
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*SE, *DT);
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}
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static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
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if (AR->getLoop() == L)
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return AR;
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return findAddRecForLoop(AR->getStart(), L);
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}
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if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
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for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
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I != E; ++I)
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if (const SCEVAddRecExpr *AR = findAddRecForLoop(*I, L))
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return AR;
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return 0;
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}
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return 0;
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}
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const SCEV *IVUsers::getStride(const IVStrideUse &IU, const Loop *L) const {
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if (const SCEVAddRecExpr *AR = findAddRecForLoop(getExpr(IU), L))
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return AR->getStepRecurrence(*SE);
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return 0;
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}
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void IVStrideUse::transformToPostInc(const Loop *L) {
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PostIncLoops.insert(L);
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}
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void IVStrideUse::deleted() {
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// Remove this user from the list.
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Parent->IVUses.erase(this);
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// this now dangles!
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}
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