--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/Analysis/IVUsers.cpp	Wed May 15 06:43:32 2013 +0900
@@ -0,0 +1,335 @@
+//===- IVUsers.cpp - Induction Variable Users -------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements bookkeeping for "interesting" users of expressions
+// computed from induction variables.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "iv-users"
+#include "llvm/Analysis/IVUsers.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Assembly/Writer.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+using namespace llvm;
+
+char IVUsers::ID = 0;
+INITIALIZE_PASS_BEGIN(IVUsers, "iv-users",
+                      "Induction Variable Users", false, true)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_PASS_END(IVUsers, "iv-users",
+                      "Induction Variable Users", false, true)
+
+Pass *llvm::createIVUsersPass() {
+  return new IVUsers();
+}
+
+/// isInteresting - Test whether the given expression is "interesting" when
+/// used by the given expression, within the context of analyzing the
+/// given loop.
+static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
+                          ScalarEvolution *SE, LoopInfo *LI) {
+  // An addrec is interesting if it's affine or if it has an interesting start.
+  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+    // Keep things simple. Don't touch loop-variant strides unless they're
+    // only used outside the loop and we can simplify them.
+    if (AR->getLoop() == L)
+      return AR->isAffine() ||
+             (!L->contains(I) &&
+              SE->getSCEVAtScope(AR, LI->getLoopFor(I->getParent())) != AR);
+    // Otherwise recurse to see if the start value is interesting, and that
+    // the step value is not interesting, since we don't yet know how to
+    // do effective SCEV expansions for addrecs with interesting steps.
+    return isInteresting(AR->getStart(), I, L, SE, LI) &&
+          !isInteresting(AR->getStepRecurrence(*SE), I, L, SE, LI);
+  }
+
+  // An add is interesting if exactly one of its operands is interesting.
+  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+    bool AnyInterestingYet = false;
+    for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
+         OI != OE; ++OI)
+      if (isInteresting(*OI, I, L, SE, LI)) {
+        if (AnyInterestingYet)
+          return false;
+        AnyInterestingYet = true;
+      }
+    return AnyInterestingYet;
+  }
+
+  // Nothing else is interesting here.
+  return false;
+}
+
+/// Return true if all loop headers that dominate this block are in simplified
+/// form.
+static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
+                                 const LoopInfo *LI,
+                                 SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+  Loop *NearestLoop = 0;
+  for (DomTreeNode *Rung = DT->getNode(BB);
+       Rung; Rung = Rung->getIDom()) {
+    BasicBlock *DomBB = Rung->getBlock();
+    Loop *DomLoop = LI->getLoopFor(DomBB);
+    if (DomLoop && DomLoop->getHeader() == DomBB) {
+      // If the domtree walk reaches a loop with no preheader, return false.
+      if (!DomLoop->isLoopSimplifyForm())
+        return false;
+      // If we have already checked this loop nest, stop checking.
+      if (SimpleLoopNests.count(DomLoop))
+        break;
+      // If we have not already checked this loop nest, remember the loop
+      // header nearest to BB. The nearest loop may not contain BB.
+      if (!NearestLoop)
+        NearestLoop = DomLoop;
+    }
+  }
+  if (NearestLoop)
+    SimpleLoopNests.insert(NearestLoop);
+  return true;
+}
+
+/// AddUsersImpl - Inspect the specified instruction.  If it is a
+/// reducible SCEV, recursively add its users to the IVUsesByStride set and
+/// return true.  Otherwise, return false.
+bool IVUsers::AddUsersImpl(Instruction *I,
+                           SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+  // Add this IV user to the Processed set before returning false to ensure that
+  // all IV users are members of the set. See IVUsers::isIVUserOrOperand.
+  if (!Processed.insert(I))
+    return true;    // Instruction already handled.
+
+  if (!SE->isSCEVable(I->getType()))
+    return false;   // Void and FP expressions cannot be reduced.
+
+  // IVUsers is used by LSR which assumes that all SCEV expressions are safe to
+  // pass to SCEVExpander. Expressions are not safe to expand if they represent
+  // operations that are not safe to speculate, namely integer division.
+  if (!isa<PHINode>(I) && !isSafeToSpeculativelyExecute(I, TD))
+    return false;
+
+  // LSR is not APInt clean, do not touch integers bigger than 64-bits.
+  // Also avoid creating IVs of non-native types. For example, we don't want a
+  // 64-bit IV in 32-bit code just because the loop has one 64-bit cast.
+  uint64_t Width = SE->getTypeSizeInBits(I->getType());
+  if (Width > 64 || (TD && !TD->isLegalInteger(Width)))
+    return false;
+
+  // Get the symbolic expression for this instruction.
+  const SCEV *ISE = SE->getSCEV(I);
+
+  // If we've come to an uninteresting expression, stop the traversal and
+  // call this a user.
+  if (!isInteresting(ISE, I, L, SE, LI))
+    return false;
+
+  SmallPtrSet<Instruction *, 4> UniqueUsers;
+  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+       UI != E; ++UI) {
+    Instruction *User = cast<Instruction>(*UI);
+    if (!UniqueUsers.insert(User))
+      continue;
+
+    // Do not infinitely recurse on PHI nodes.
+    if (isa<PHINode>(User) && Processed.count(User))
+      continue;
+
+    // Only consider IVUsers that are dominated by simplified loop
+    // headers. Otherwise, SCEVExpander will crash.
+    BasicBlock *UseBB = User->getParent();
+    // A phi's use is live out of its predecessor block.
+    if (PHINode *PHI = dyn_cast<PHINode>(User)) {
+      unsigned OperandNo = UI.getOperandNo();
+      unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
+      UseBB = PHI->getIncomingBlock(ValNo);
+    }
+    if (!isSimplifiedLoopNest(UseBB, DT, LI, SimpleLoopNests))
+      return false;
+
+    // Descend recursively, but not into PHI nodes outside the current loop.
+    // It's important to see the entire expression outside the loop to get
+    // choices that depend on addressing mode use right, although we won't
+    // consider references outside the loop in all cases.
+    // If User is already in Processed, we don't want to recurse into it again,
+    // but do want to record a second reference in the same instruction.
+    bool AddUserToIVUsers = false;
+    if (LI->getLoopFor(User->getParent()) != L) {
+      if (isa<PHINode>(User) || Processed.count(User) ||
+          !AddUsersImpl(User, SimpleLoopNests)) {
+        DEBUG(dbgs() << "FOUND USER in other loop: " << *User << '\n'
+                     << "   OF SCEV: " << *ISE << '\n');
+        AddUserToIVUsers = true;
+      }
+    } else if (Processed.count(User) || !AddUsersImpl(User, SimpleLoopNests)) {
+      DEBUG(dbgs() << "FOUND USER: " << *User << '\n'
+                   << "   OF SCEV: " << *ISE << '\n');
+      AddUserToIVUsers = true;
+    }
+
+    if (AddUserToIVUsers) {
+      // Okay, we found a user that we cannot reduce.
+      IVUses.push_back(new IVStrideUse(this, User, I));
+      IVStrideUse &NewUse = IVUses.back();
+      // Autodetect the post-inc loop set, populating NewUse.PostIncLoops.
+      // The regular return value here is discarded; instead of recording
+      // it, we just recompute it when we need it.
+      ISE = TransformForPostIncUse(NormalizeAutodetect,
+                                   ISE, User, I,
+                                   NewUse.PostIncLoops,
+                                   *SE, *DT);
+      DEBUG(if (SE->getSCEV(I) != ISE)
+              dbgs() << "   NORMALIZED TO: " << *ISE << '\n');
+    }
+  }
+  return true;
+}
+
+bool IVUsers::AddUsersIfInteresting(Instruction *I) {
+  // SCEVExpander can only handle users that are dominated by simplified loop
+  // entries. Keep track of all loops that are only dominated by other simple
+  // loops so we don't traverse the domtree for each user.
+  SmallPtrSet<Loop*,16> SimpleLoopNests;
+
+  return AddUsersImpl(I, SimpleLoopNests);
+}
+
+IVStrideUse &IVUsers::AddUser(Instruction *User, Value *Operand) {
+  IVUses.push_back(new IVStrideUse(this, User, Operand));
+  return IVUses.back();
+}
+
+IVUsers::IVUsers()
+    : LoopPass(ID) {
+  initializeIVUsersPass(*PassRegistry::getPassRegistry());
+}
+
+void IVUsers::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<LoopInfo>();
+  AU.addRequired<DominatorTree>();
+  AU.addRequired<ScalarEvolution>();
+  AU.setPreservesAll();
+}
+
+bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
+
+  L = l;
+  LI = &getAnalysis<LoopInfo>();
+  DT = &getAnalysis<DominatorTree>();
+  SE = &getAnalysis<ScalarEvolution>();
+  TD = getAnalysisIfAvailable<DataLayout>();
+
+  // Find all uses of induction variables in this loop, and categorize
+  // them by stride.  Start by finding all of the PHI nodes in the header for
+  // this loop.  If they are induction variables, inspect their uses.
+  for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
+    (void)AddUsersIfInteresting(I);
+
+  return false;
+}
+
+void IVUsers::print(raw_ostream &OS, const Module *M) const {
+  OS << "IV Users for loop ";
+  WriteAsOperand(OS, L->getHeader(), false);
+  if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
+    OS << " with backedge-taken count "
+       << *SE->getBackedgeTakenCount(L);
+  }
+  OS << ":\n";
+
+  for (ilist<IVStrideUse>::const_iterator UI = IVUses.begin(),
+       E = IVUses.end(); UI != E; ++UI) {
+    OS << "  ";
+    WriteAsOperand(OS, UI->getOperandValToReplace(), false);
+    OS << " = " << *getReplacementExpr(*UI);
+    for (PostIncLoopSet::const_iterator
+         I = UI->PostIncLoops.begin(),
+         E = UI->PostIncLoops.end(); I != E; ++I) {
+      OS << " (post-inc with loop ";
+      WriteAsOperand(OS, (*I)->getHeader(), false);
+      OS << ")";
+    }
+    OS << " in  ";
+    UI->getUser()->print(OS);
+    OS << '\n';
+  }
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+void IVUsers::dump() const {
+  print(dbgs());
+}
+#endif
+
+void IVUsers::releaseMemory() {
+  Processed.clear();
+  IVUses.clear();
+}
+
+/// getReplacementExpr - Return a SCEV expression which computes the
+/// value of the OperandValToReplace.
+const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &IU) const {
+  return SE->getSCEV(IU.getOperandValToReplace());
+}
+
+/// getExpr - Return the expression for the use.
+const SCEV *IVUsers::getExpr(const IVStrideUse &IU) const {
+  return
+    TransformForPostIncUse(Normalize, getReplacementExpr(IU),
+                           IU.getUser(), IU.getOperandValToReplace(),
+                           const_cast<PostIncLoopSet &>(IU.getPostIncLoops()),
+                           *SE, *DT);
+}
+
+static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
+  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+    if (AR->getLoop() == L)
+      return AR;
+    return findAddRecForLoop(AR->getStart(), L);
+  }
+
+  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
+         I != E; ++I)
+      if (const SCEVAddRecExpr *AR = findAddRecForLoop(*I, L))
+        return AR;
+    return 0;
+  }
+
+  return 0;
+}
+
+const SCEV *IVUsers::getStride(const IVStrideUse &IU, const Loop *L) const {
+  if (const SCEVAddRecExpr *AR = findAddRecForLoop(getExpr(IU), L))
+    return AR->getStepRecurrence(*SE);
+  return 0;
+}
+
+void IVStrideUse::transformToPostInc(const Loop *L) {
+  PostIncLoops.insert(L);
+}
+
+void IVStrideUse::deleted() {
+  // Remove this user from the list.
+  Parent->Processed.erase(this->getUser());
+  Parent->IVUses.erase(this);
+  // this now dangles!
+}