//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "indvars"
-
-#include "llvm/Instructions.h"
-#include "llvm/Analysis/Dominators.h"
+#include "llvm/Transforms/Utils/SimplifyIndVar.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/IVUsers.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Utils/SimplifyIndVar.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
using namespace llvm;
+#define DEBUG_TYPE "indvars"
+
STATISTIC(NumElimIdentity, "Number of IV identities eliminated");
STATISTIC(NumElimOperand, "Number of IV operands folded into a use");
STATISTIC(NumElimRem , "Number of IV remainder operations eliminated");
class SimplifyIndvar {
Loop *L;
LoopInfo *LI;
- DominatorTree *DT;
ScalarEvolution *SE;
- IVUsers *IU; // NULL for DisableIVRewrite
- const TargetData *TD; // May be NULL
+ const DataLayout *DL; // May be NULL
SmallVectorImpl<WeakVH> &DeadInsts;
public:
SimplifyIndvar(Loop *Loop, ScalarEvolution *SE, LPPassManager *LPM,
- SmallVectorImpl<WeakVH> &Dead, IVUsers *IVU = NULL) :
+ SmallVectorImpl<WeakVH> &Dead, IVUsers *IVU = nullptr) :
L(Loop),
LI(LPM->getAnalysisIfAvailable<LoopInfo>()),
SE(SE),
- IU(IVU),
- TD(LPM->getAnalysisIfAvailable<TargetData>()),
DeadInsts(Dead),
Changed(false) {
+ DataLayoutPass *DLP = LPM->getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : nullptr;
assert(LI && "IV simplification requires LoopInfo");
}
/// Iteratively perform simplification on a worklist of users of the
/// specified induction variable. This is the top-level driver that applies
/// all simplicitions to users of an IV.
- void simplifyUsers(PHINode *CurrIV, IVVisitor *V = NULL);
+ void simplifyUsers(PHINode *CurrIV, IVVisitor *V = nullptr);
Value *foldIVUser(Instruction *UseInst, Instruction *IVOperand);
void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
bool IsSigned);
+
+ Instruction *splitOverflowIntrinsic(Instruction *IVUser,
+ const DominatorTree *DT);
};
}
/// be folded (in case more folding opportunities have been exposed).
/// Otherwise return null.
Value *SimplifyIndvar::foldIVUser(Instruction *UseInst, Instruction *IVOperand) {
- Value *IVSrc = 0;
+ Value *IVSrc = nullptr;
unsigned OperIdx = 0;
- const SCEV *FoldedExpr = 0;
+ const SCEV *FoldedExpr = nullptr;
switch (UseInst->getOpcode()) {
default:
- return 0;
+ return nullptr;
case Instruction::UDiv:
case Instruction::LShr:
// We're only interested in the case where we know something about
// the numerator and have a constant denominator.
if (IVOperand != UseInst->getOperand(OperIdx) ||
!isa<ConstantInt>(UseInst->getOperand(1)))
- return 0;
+ return nullptr;
// Attempt to fold a binary operator with constant operand.
// e.g. ((I + 1) >> 2) => I >> 2
if (!isa<BinaryOperator>(IVOperand)
|| !isa<ConstantInt>(IVOperand->getOperand(1)))
- return 0;
+ return nullptr;
IVSrc = IVOperand->getOperand(0);
// IVSrc must be the (SCEVable) IV, since the other operand is const.
// Get a constant for the divisor. See createSCEV.
uint32_t BitWidth = cast<IntegerType>(UseInst->getType())->getBitWidth();
if (D->getValue().uge(BitWidth))
- return 0;
+ return nullptr;
D = ConstantInt::get(UseInst->getContext(),
- APInt(BitWidth, 1).shl(D->getZExtValue()));
+ APInt::getOneBitSet(BitWidth, D->getZExtValue()));
}
FoldedExpr = SE->getUDivExpr(SE->getSCEV(IVSrc), SE->getSCEV(D));
}
// We have something that might fold it's operand. Compare SCEVs.
if (!SE->isSCEVable(UseInst->getType()))
- return 0;
+ return nullptr;
// Bypass the operand if SCEV can prove it has no effect.
if (SE->getSCEV(UseInst) != FoldedExpr)
- return 0;
+ return nullptr;
DEBUG(dbgs() << "INDVARS: Eliminated IV operand: " << *IVOperand
<< " -> " << *UseInst << '\n');
Rem->replaceAllUsesWith(Sel);
}
- // Inform IVUsers about the new users.
- if (IU) {
- if (Instruction *I = dyn_cast<Instruction>(Rem->getOperand(0))) {
- SmallPtrSet<Loop*, 16> SimplifiedLoopNests;
- IU->AddUsersIfInteresting(I, SimplifiedLoopNests);
- }
- }
DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
++NumElimRem;
Changed = true;
return true;
}
+/// \brief Split sadd.with.overflow into add + sadd.with.overflow to allow
+/// analysis and optimization.
+///
+/// \return A new value representing the non-overflowing add if possible,
+/// otherwise return the original value.
+Instruction *SimplifyIndvar::splitOverflowIntrinsic(Instruction *IVUser,
+ const DominatorTree *DT) {
+ IntrinsicInst *II = dyn_cast<IntrinsicInst>(IVUser);
+ if (!II || II->getIntrinsicID() != Intrinsic::sadd_with_overflow)
+ return IVUser;
+
+ // Find a branch guarded by the overflow check.
+ BranchInst *Branch = nullptr;
+ Instruction *AddVal = nullptr;
+ for (User *U : II->users()) {
+ if (ExtractValueInst *ExtractInst = dyn_cast<ExtractValueInst>(U)) {
+ if (ExtractInst->getNumIndices() != 1)
+ continue;
+ if (ExtractInst->getIndices()[0] == 0)
+ AddVal = ExtractInst;
+ else if (ExtractInst->getIndices()[0] == 1 && ExtractInst->hasOneUse())
+ Branch = dyn_cast<BranchInst>(ExtractInst->user_back());
+ }
+ }
+ if (!AddVal || !Branch)
+ return IVUser;
+
+ BasicBlock *ContinueBB = Branch->getSuccessor(1);
+ if (std::next(pred_begin(ContinueBB)) != pred_end(ContinueBB))
+ return IVUser;
+
+ // Check if all users of the add are provably NSW.
+ bool AllNSW = true;
+ for (Use &U : AddVal->uses()) {
+ if (Instruction *UseInst = dyn_cast<Instruction>(U.getUser())) {
+ BasicBlock *UseBB = UseInst->getParent();
+ if (PHINode *PHI = dyn_cast<PHINode>(UseInst))
+ UseBB = PHI->getIncomingBlock(U);
+ if (!DT->dominates(ContinueBB, UseBB)) {
+ AllNSW = false;
+ break;
+ }
+ }
+ }
+ if (!AllNSW)
+ return IVUser;
+
+ // Go for it...
+ IRBuilder<> Builder(IVUser);
+ Instruction *AddInst = dyn_cast<Instruction>(
+ Builder.CreateNSWAdd(II->getOperand(0), II->getOperand(1)));
+
+ // The caller expects the new add to have the same form as the intrinsic. The
+ // IV operand position must be the same.
+ assert((AddInst->getOpcode() == Instruction::Add &&
+ AddInst->getOperand(0) == II->getOperand(0)) &&
+ "Bad add instruction created from overflow intrinsic.");
+
+ AddVal->replaceAllUsesWith(AddInst);
+ DeadInsts.push_back(AddVal);
+ return AddInst;
+}
+
/// pushIVUsers - Add all uses of Def to the current IV's worklist.
///
static void pushIVUsers(
SmallPtrSet<Instruction*,16> &Simplified,
SmallVectorImpl< std::pair<Instruction*,Instruction*> > &SimpleIVUsers) {
- for (Value::use_iterator UI = Def->use_begin(), E = Def->use_end();
- UI != E; ++UI) {
- Instruction *User = cast<Instruction>(*UI);
+ for (User *U : Def->users()) {
+ Instruction *UI = cast<Instruction>(U);
// Avoid infinite or exponential worklist processing.
// Also ensure unique worklist users.
// If Def is a LoopPhi, it may not be in the Simplified set, so check for
// self edges first.
- if (User != Def && Simplified.insert(User))
- SimpleIVUsers.push_back(std::make_pair(User, Def));
+ if (UI != Def && Simplified.insert(UI))
+ SimpleIVUsers.push_back(std::make_pair(UI, Def));
}
}
while (!SimpleIVUsers.empty()) {
std::pair<Instruction*, Instruction*> UseOper =
SimpleIVUsers.pop_back_val();
+ Instruction *UseInst = UseOper.first;
+
// Bypass back edges to avoid extra work.
- if (UseOper.first == CurrIV) continue;
+ if (UseInst == CurrIV) continue;
+
+ if (V && V->shouldSplitOverflowInstrinsics()) {
+ UseInst = splitOverflowIntrinsic(UseInst, V->getDomTree());
+ if (!UseInst)
+ continue;
+ }
Instruction *IVOperand = UseOper.second;
for (unsigned N = 0; IVOperand; ++N) {
return Changed;
}
-/// simplifyIVUsers - Perform simplification on instructions recorded by the
-/// IVUsers pass.
-///
-/// This is the old approach to IV simplification to be replaced by
-/// SimplifyLoopIVs.
-bool simplifyIVUsers(IVUsers *IU, ScalarEvolution *SE, LPPassManager *LPM,
- SmallVectorImpl<WeakVH> &Dead) {
- SimplifyIndvar SIV(IU->getLoop(), SE, LPM, Dead);
-
- // Each round of simplification involves a round of eliminating operations
- // followed by a round of widening IVs. A single IVUsers worklist is used
- // across all rounds. The inner loop advances the user. If widening exposes
- // more uses, then another pass through the outer loop is triggered.
- for (IVUsers::iterator I = IU->begin(); I != IU->end(); ++I) {
- Instruction *UseInst = I->getUser();
- Value *IVOperand = I->getOperandValToReplace();
-
- if (ICmpInst *ICmp = dyn_cast<ICmpInst>(UseInst)) {
- SIV.eliminateIVComparison(ICmp, IVOperand);
- continue;
- }
- if (BinaryOperator *Rem = dyn_cast<BinaryOperator>(UseInst)) {
- bool IsSigned = Rem->getOpcode() == Instruction::SRem;
- if (IsSigned || Rem->getOpcode() == Instruction::URem) {
- SIV.eliminateIVRemainder(Rem, IVOperand, IsSigned);
- continue;
- }
- }
- }
- return SIV.hasChanged();
-}
-
} // namespace llvm
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