-//===- ScalarEvolution.cpp - Scalar Evolution Analysis ----------*- C++ -*-===//
+//===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===//
//
// The LLVM Compiler Infrastructure
//
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "scalar-evolution"
#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionTracker.h"
#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Assembly/Writer.h"
+#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Metadata.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
-#include "llvm/Support/InstIterator.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include <algorithm>
using namespace llvm;
+#define DEBUG_TYPE "scalar-evolution"
+
STATISTIC(NumArrayLenItCounts,
"Number of trip counts computed with array length");
STATISTIC(NumTripCountsComputed,
INITIALIZE_PASS_BEGIN(ScalarEvolution, "scalar-evolution",
"Scalar Evolution Analysis", false, true)
+INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_PASS_END(ScalarEvolution, "scalar-evolution",
"Scalar Evolution Analysis", false, true)
#endif
void SCEV::print(raw_ostream &OS) const {
- switch (getSCEVType()) {
+ switch (static_cast<SCEVTypes>(getSCEVType())) {
case scConstant:
- WriteAsOperand(OS, cast<SCEVConstant>(this)->getValue(), false);
+ cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
return;
case scTruncate: {
const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
if (AR->getNoWrapFlags(FlagNW) &&
!AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
OS << "nw><";
- WriteAsOperand(OS, AR->getLoop()->getHeader(), /*PrintType=*/false);
+ AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
OS << ">";
return;
}
case scUMaxExpr:
case scSMaxExpr: {
const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
- const char *OpStr = 0;
+ const char *OpStr = nullptr;
switch (NAry->getSCEVType()) {
case scAddExpr: OpStr = " + "; break;
case scMulExpr: OpStr = " * "; break;
for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
I != E; ++I) {
OS << **I;
- if (llvm::next(I) != E)
+ if (std::next(I) != E)
OS << OpStr;
}
OS << ")";
Constant *FieldNo;
if (U->isOffsetOf(CTy, FieldNo)) {
OS << "offsetof(" << *CTy << ", ";
- WriteAsOperand(OS, FieldNo, false);
+ FieldNo->printAsOperand(OS, false);
OS << ")";
return;
}
// Otherwise just print it normally.
- WriteAsOperand(OS, U->getValue(), false);
+ U->getValue()->printAsOperand(OS, false);
return;
}
case scCouldNotCompute:
OS << "***COULDNOTCOMPUTE***";
return;
- default: break;
}
llvm_unreachable("Unknown SCEV kind!");
}
Type *SCEV::getType() const {
- switch (getSCEVType()) {
+ switch (static_cast<SCEVTypes>(getSCEVType())) {
case scConstant:
return cast<SCEVConstant>(this)->getType();
case scTruncate:
return cast<SCEVUnknown>(this)->getType();
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
- default:
- llvm_unreachable("Unknown SCEV kind!");
}
+ llvm_unreachable("Unknown SCEV kind!");
}
bool SCEV::isZero() const {
FoldingSetNodeID ID;
ID.AddInteger(scConstant);
ID.AddPointer(V);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
UniqueSCEVs.InsertNode(S, IP);
return S;
}
-const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
+const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
return getConstant(ConstantInt::get(getContext(), Val));
}
SE->UniqueSCEVs.RemoveNode(this);
// Release the value.
- setValPtr(0);
+ setValPtr(nullptr);
}
void SCEVUnknown::allUsesReplacedWith(Value *New) {
// Aside from the getSCEVType() ordering, the particular ordering
// isn't very important except that it's beneficial to be consistent,
// so that (a + b) and (b + a) don't end up as different expressions.
- switch (LType) {
+ switch (static_cast<SCEVTypes>(LType)) {
case scUnknown: {
const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
// Lexicographically compare n-ary expressions.
unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
+ if (LNumOps != RNumOps)
+ return (int)LNumOps - (int)RNumOps;
+
for (unsigned i = 0; i != LNumOps; ++i) {
if (i >= RNumOps)
return 1;
return compare(LC->getOperand(), RC->getOperand());
}
- default:
- llvm_unreachable("Unknown SCEV kind!");
+ case scCouldNotCompute:
+ llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
}
+ llvm_unreachable("Unknown SCEV kind!");
}
};
}
}
}
+static const APInt srem(const SCEVConstant *C1, const SCEVConstant *C2) {
+ APInt A = C1->getValue()->getValue();
+ APInt B = C2->getValue()->getValue();
+ uint32_t ABW = A.getBitWidth();
+ uint32_t BBW = B.getBitWidth();
+
+ if (ABW > BBW)
+ B = B.sext(ABW);
+ else if (ABW < BBW)
+ A = A.sext(BBW);
+
+ return APIntOps::srem(A, B);
+}
+
+static const APInt sdiv(const SCEVConstant *C1, const SCEVConstant *C2) {
+ APInt A = C1->getValue()->getValue();
+ APInt B = C2->getValue()->getValue();
+ uint32_t ABW = A.getBitWidth();
+ uint32_t BBW = B.getBitWidth();
+
+ if (ABW > BBW)
+ B = B.sext(ABW);
+ else if (ABW < BBW)
+ A = A.sext(BBW);
+
+ return APIntOps::sdiv(A, B);
+}
+
+static const APInt urem(const SCEVConstant *C1, const SCEVConstant *C2) {
+ APInt A = C1->getValue()->getValue();
+ APInt B = C2->getValue()->getValue();
+ uint32_t ABW = A.getBitWidth();
+ uint32_t BBW = B.getBitWidth();
+
+ if (ABW > BBW)
+ B = B.zext(ABW);
+ else if (ABW < BBW)
+ A = A.zext(BBW);
+
+ return APIntOps::urem(A, B);
+}
+
+static const APInt udiv(const SCEVConstant *C1, const SCEVConstant *C2) {
+ APInt A = C1->getValue()->getValue();
+ APInt B = C2->getValue()->getValue();
+ uint32_t ABW = A.getBitWidth();
+ uint32_t BBW = B.getBitWidth();
+
+ if (ABW > BBW)
+ B = B.zext(ABW);
+ else if (ABW < BBW)
+ A = A.zext(BBW);
+
+ return APIntOps::udiv(A, B);
+}
+
+namespace {
+struct FindSCEVSize {
+ int Size;
+ FindSCEVSize() : Size(0) {}
+
+ bool follow(const SCEV *S) {
+ ++Size;
+ // Keep looking at all operands of S.
+ return true;
+ }
+ bool isDone() const {
+ return false;
+ }
+};
+}
+
+// Returns the size of the SCEV S.
+static inline int sizeOfSCEV(const SCEV *S) {
+ FindSCEVSize F;
+ SCEVTraversal<FindSCEVSize> ST(F);
+ ST.visitAll(S);
+ return F.Size;
+}
+
+namespace {
+
+template <typename Derived>
+struct SCEVDivision : public SCEVVisitor<Derived, void> {
+public:
+ // Computes the Quotient and Remainder of the division of Numerator by
+ // Denominator.
+ static void divide(ScalarEvolution &SE, const SCEV *Numerator,
+ const SCEV *Denominator, const SCEV **Quotient,
+ const SCEV **Remainder) {
+ assert(Numerator && Denominator && "Uninitialized SCEV");
+
+ Derived D(SE, Numerator, Denominator);
+
+ // Check for the trivial case here to avoid having to check for it in the
+ // rest of the code.
+ if (Numerator == Denominator) {
+ *Quotient = D.One;
+ *Remainder = D.Zero;
+ return;
+ }
+
+ if (Numerator->isZero()) {
+ *Quotient = D.Zero;
+ *Remainder = D.Zero;
+ return;
+ }
+
+ // Split the Denominator when it is a product.
+ if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
+ const SCEV *Q, *R;
+ *Quotient = Numerator;
+ for (const SCEV *Op : T->operands()) {
+ divide(SE, *Quotient, Op, &Q, &R);
+ *Quotient = Q;
+
+ // Bail out when the Numerator is not divisible by one of the terms of
+ // the Denominator.
+ if (!R->isZero()) {
+ *Quotient = D.Zero;
+ *Remainder = Numerator;
+ return;
+ }
+ }
+ *Remainder = D.Zero;
+ return;
+ }
+
+ D.visit(Numerator);
+ *Quotient = D.Quotient;
+ *Remainder = D.Remainder;
+ }
+
+ // Except in the trivial case described above, we do not know how to divide
+ // Expr by Denominator for the following functions with empty implementation.
+ void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
+ void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
+ void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
+ void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
+ void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
+ void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
+ void visitUnknown(const SCEVUnknown *Numerator) {}
+ void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
+
+ void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
+ const SCEV *StartQ, *StartR, *StepQ, *StepR;
+ assert(Numerator->isAffine() && "Numerator should be affine");
+ divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
+ divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
+ Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
+ Numerator->getNoWrapFlags());
+ Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
+ Numerator->getNoWrapFlags());
+ }
+
+ void visitAddExpr(const SCEVAddExpr *Numerator) {
+ SmallVector<const SCEV *, 2> Qs, Rs;
+ Type *Ty = Denominator->getType();
+
+ for (const SCEV *Op : Numerator->operands()) {
+ const SCEV *Q, *R;
+ divide(SE, Op, Denominator, &Q, &R);
+
+ // Bail out if types do not match.
+ if (Ty != Q->getType() || Ty != R->getType()) {
+ Quotient = Zero;
+ Remainder = Numerator;
+ return;
+ }
+
+ Qs.push_back(Q);
+ Rs.push_back(R);
+ }
+
+ if (Qs.size() == 1) {
+ Quotient = Qs[0];
+ Remainder = Rs[0];
+ return;
+ }
+
+ Quotient = SE.getAddExpr(Qs);
+ Remainder = SE.getAddExpr(Rs);
+ }
+
+ void visitMulExpr(const SCEVMulExpr *Numerator) {
+ SmallVector<const SCEV *, 2> Qs;
+ Type *Ty = Denominator->getType();
+
+ bool FoundDenominatorTerm = false;
+ for (const SCEV *Op : Numerator->operands()) {
+ // Bail out if types do not match.
+ if (Ty != Op->getType()) {
+ Quotient = Zero;
+ Remainder = Numerator;
+ return;
+ }
+
+ if (FoundDenominatorTerm) {
+ Qs.push_back(Op);
+ continue;
+ }
+
+ // Check whether Denominator divides one of the product operands.
+ const SCEV *Q, *R;
+ divide(SE, Op, Denominator, &Q, &R);
+ if (!R->isZero()) {
+ Qs.push_back(Op);
+ continue;
+ }
+
+ // Bail out if types do not match.
+ if (Ty != Q->getType()) {
+ Quotient = Zero;
+ Remainder = Numerator;
+ return;
+ }
+
+ FoundDenominatorTerm = true;
+ Qs.push_back(Q);
+ }
+
+ if (FoundDenominatorTerm) {
+ Remainder = Zero;
+ if (Qs.size() == 1)
+ Quotient = Qs[0];
+ else
+ Quotient = SE.getMulExpr(Qs);
+ return;
+ }
+
+ if (!isa<SCEVUnknown>(Denominator)) {
+ Quotient = Zero;
+ Remainder = Numerator;
+ return;
+ }
+
+ // The Remainder is obtained by replacing Denominator by 0 in Numerator.
+ ValueToValueMap RewriteMap;
+ RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
+ cast<SCEVConstant>(Zero)->getValue();
+ Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
+
+ if (Remainder->isZero()) {
+ // The Quotient is obtained by replacing Denominator by 1 in Numerator.
+ RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
+ cast<SCEVConstant>(One)->getValue();
+ Quotient =
+ SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
+ return;
+ }
+
+ // Quotient is (Numerator - Remainder) divided by Denominator.
+ const SCEV *Q, *R;
+ const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
+ if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator)) {
+ // This SCEV does not seem to simplify: fail the division here.
+ Quotient = Zero;
+ Remainder = Numerator;
+ return;
+ }
+ divide(SE, Diff, Denominator, &Q, &R);
+ assert(R == Zero &&
+ "(Numerator - Remainder) should evenly divide Denominator");
+ Quotient = Q;
+ }
+
+private:
+ SCEVDivision(ScalarEvolution &S, const SCEV *Numerator,
+ const SCEV *Denominator)
+ : SE(S), Denominator(Denominator) {
+ Zero = SE.getConstant(Denominator->getType(), 0);
+ One = SE.getConstant(Denominator->getType(), 1);
+
+ // By default, we don't know how to divide Expr by Denominator.
+ // Providing the default here simplifies the rest of the code.
+ Quotient = Zero;
+ Remainder = Numerator;
+ }
+
+ ScalarEvolution &SE;
+ const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
+
+ friend struct SCEVSDivision;
+ friend struct SCEVUDivision;
+};
+
+struct SCEVSDivision : public SCEVDivision<SCEVSDivision> {
+ SCEVSDivision(ScalarEvolution &S, const SCEV *Numerator,
+ const SCEV *Denominator)
+ : SCEVDivision(S, Numerator, Denominator) {}
+
+ void visitConstant(const SCEVConstant *Numerator) {
+ if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
+ Quotient = SE.getConstant(sdiv(Numerator, D));
+ Remainder = SE.getConstant(srem(Numerator, D));
+ return;
+ }
+ }
+};
+
+struct SCEVUDivision : public SCEVDivision<SCEVUDivision> {
+ SCEVUDivision(ScalarEvolution &S, const SCEV *Numerator,
+ const SCEV *Denominator)
+ : SCEVDivision(S, Numerator, Denominator) {}
+
+ void visitConstant(const SCEVConstant *Numerator) {
+ if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
+ Quotient = SE.getConstant(udiv(Numerator, D));
+ Remainder = SE.getConstant(urem(Numerator, D));
+ return;
+ }
+ }
+};
+}
//===----------------------------------------------------------------------===//
// Simple SCEV method implementations
ID.AddInteger(scTruncate);
ID.AddPointer(Op);
ID.AddPointer(Ty);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
// Fold if the operand is constant.
ID.AddInteger(scZeroExtend);
ID.AddPointer(Op);
ID.AddPointer(Ty);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
// zext(trunc(x)) --> zext(x) or x or trunc(x)
return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
SE->getSignedRange(Step).getSignedMin());
}
- return 0;
+ return nullptr;
}
// The recurrence AR has been shown to have no signed wrap. Typically, if we can
// Check for a simple looking step prior to loop entry.
const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
if (!SA)
- return 0;
+ return nullptr;
// Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
// subtraction is expensive. For this purpose, perform a quick and dirty
// difference, by checking for Step in the operand list.
SmallVector<const SCEV *, 4> DiffOps;
- for (SCEVAddExpr::op_iterator I = SA->op_begin(), E = SA->op_end();
- I != E; ++I) {
- if (*I != Step)
- DiffOps.push_back(*I);
- }
+ for (const SCEV *Op : SA->operands())
+ if (Op != Step)
+ DiffOps.push_back(Op);
+
if (DiffOps.size() == SA->getNumOperands())
- return 0;
+ return nullptr;
// This is a postinc AR. Check for overflow on the preinc recurrence using the
// same three conditions that getSignExtendedExpr checks.
SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) {
return PreStart;
}
- return 0;
+ return nullptr;
}
// Get the normalized sign-extended expression for this AddRec's Start.
ID.AddInteger(scSignExtend);
ID.AddPointer(Op);
ID.AddPointer(Ty);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
// If the input value is provably positive, build a zext instead.
return getTruncateOrSignExtend(X, Ty);
}
+ // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
+ if (auto SA = dyn_cast<SCEVAddExpr>(Op)) {
+ if (SA->getNumOperands() == 2) {
+ auto SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
+ auto SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
+ if (SMul && SC1) {
+ if (auto SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
+ const APInt &C1 = SC1->getValue()->getValue();
+ const APInt &C2 = SC2->getValue()->getValue();
+ if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
+ C2.ugt(C1) && C2.isPowerOf2())
+ return getAddExpr(getSignExtendExpr(SC1, Ty),
+ getSignExtendExpr(SMul, Ty));
+ }
+ }
+ }
+ }
// If the input value is a chrec scev, and we can prove that the value
// did not overflow the old, smaller, value, we can sign extend all of the
// operands (often constants). This allows analysis of something like
L, AR->getNoWrapFlags());
}
}
+ // If Start and Step are constants, check if we can apply this
+ // transformation:
+ // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
+ auto SC1 = dyn_cast<SCEVConstant>(Start);
+ auto SC2 = dyn_cast<SCEVConstant>(Step);
+ if (SC1 && SC2) {
+ const APInt &C1 = SC1->getValue()->getValue();
+ const APInt &C2 = SC2->getValue()->getValue();
+ if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
+ C2.isPowerOf2()) {
+ Start = getSignExtendExpr(Start, Ty);
+ const SCEV *NewAR = getAddRecExpr(getConstant(AR->getType(), 0), Step,
+ L, AR->getNoWrapFlags());
+ return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
+ }
+ }
}
// The cast wasn't folded; create an explicit cast node.
// Force the cast to be folded into the operands of an addrec.
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
SmallVector<const SCEV *, 4> Ops;
- for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
- I != E; ++I)
- Ops.push_back(getAnyExtendExpr(*I, Ty));
+ for (const SCEV *Op : AR->operands())
+ Ops.push_back(getAnyExtendExpr(Op, Ty));
return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
}
/// what it does, given a sequence of operands that would form an add
/// expression like this:
///
-/// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
+/// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
///
/// where A and B are constants, update the map with these values:
///
ID.AddInteger(scAddExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
- void *IP = 0;
+ void *IP = nullptr;
SCEVAddExpr *S =
static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
if (!S) {
return r;
}
+/// Determine if any of the operands in this SCEV are a constant or if
+/// any of the add or multiply expressions in this SCEV contain a constant.
+static bool containsConstantSomewhere(const SCEV *StartExpr) {
+ SmallVector<const SCEV *, 4> Ops;
+ Ops.push_back(StartExpr);
+ while (!Ops.empty()) {
+ const SCEV *CurrentExpr = Ops.pop_back_val();
+ if (isa<SCEVConstant>(*CurrentExpr))
+ return true;
+
+ if (isa<SCEVAddExpr>(*CurrentExpr) || isa<SCEVMulExpr>(*CurrentExpr)) {
+ const auto *CurrentNAry = cast<SCEVNAryExpr>(CurrentExpr);
+ for (const SCEV *Operand : CurrentNAry->operands())
+ Ops.push_back(Operand);
+ }
+ }
+ return false;
+}
+
/// getMulExpr - Get a canonical multiply expression, or something simpler if
/// possible.
const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
// C1*(C2+V) -> C1*C2 + C1*V
if (Ops.size() == 2)
- if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
- if (Add->getNumOperands() == 2 &&
- isa<SCEVConstant>(Add->getOperand(0)))
- return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
- getMulExpr(LHSC, Add->getOperand(1)));
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
+ // If any of Add's ops are Adds or Muls with a constant,
+ // apply this transformation as well.
+ if (Add->getNumOperands() == 2)
+ if (containsConstantSomewhere(Add))
+ return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
+ getMulExpr(LHSC, Add->getOperand(1)));
++Idx;
while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
// Okay, if there weren't any loop invariants to be folded, check to see if
// there are multiple AddRec's with the same loop induction variable being
// multiplied together. If so, we can fold them.
+
+ // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
+ // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
+ // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
+ // ]]],+,...up to x=2n}.
+ // Note that the arguments to choose() are always integers with values
+ // known at compile time, never SCEV objects.
+ //
+ // The implementation avoids pointless extra computations when the two
+ // addrec's are of different length (mathematically, it's equivalent to
+ // an infinite stream of zeros on the right).
+ bool OpsModified = false;
for (unsigned OtherIdx = Idx+1;
- OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
+ OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
++OtherIdx) {
- if (AddRecLoop != cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop())
+ const SCEVAddRecExpr *OtherAddRec =
+ dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
+ if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
continue;
- // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
- // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
- // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
- // ]]],+,...up to x=2n}.
- // Note that the arguments to choose() are always integers with values
- // known at compile time, never SCEV objects.
- //
- // The implementation avoids pointless extra computations when the two
- // addrec's are of different length (mathematically, it's equivalent to
- // an infinite stream of zeros on the right).
- bool OpsModified = false;
- for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
- ++OtherIdx) {
- const SCEVAddRecExpr *OtherAddRec =
- dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
- if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
- continue;
-
- bool Overflow = false;
- Type *Ty = AddRec->getType();
- bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
- SmallVector<const SCEV*, 7> AddRecOps;
- for (int x = 0, xe = AddRec->getNumOperands() +
- OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
- const SCEV *Term = getConstant(Ty, 0);
- for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
- uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
- for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
- ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
- z < ze && !Overflow; ++z) {
- uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
- uint64_t Coeff;
- if (LargerThan64Bits)
- Coeff = umul_ov(Coeff1, Coeff2, Overflow);
- else
- Coeff = Coeff1*Coeff2;
- const SCEV *CoeffTerm = getConstant(Ty, Coeff);
- const SCEV *Term1 = AddRec->getOperand(y-z);
- const SCEV *Term2 = OtherAddRec->getOperand(z);
- Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
- }
+ bool Overflow = false;
+ Type *Ty = AddRec->getType();
+ bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
+ SmallVector<const SCEV*, 7> AddRecOps;
+ for (int x = 0, xe = AddRec->getNumOperands() +
+ OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
+ const SCEV *Term = getConstant(Ty, 0);
+ for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
+ uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
+ for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
+ ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
+ z < ze && !Overflow; ++z) {
+ uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
+ uint64_t Coeff;
+ if (LargerThan64Bits)
+ Coeff = umul_ov(Coeff1, Coeff2, Overflow);
+ else
+ Coeff = Coeff1*Coeff2;
+ const SCEV *CoeffTerm = getConstant(Ty, Coeff);
+ const SCEV *Term1 = AddRec->getOperand(y-z);
+ const SCEV *Term2 = OtherAddRec->getOperand(z);
+ Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
}
- AddRecOps.push_back(Term);
- }
- if (!Overflow) {
- const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
- SCEV::FlagAnyWrap);
- if (Ops.size() == 2) return NewAddRec;
- Ops[Idx] = NewAddRec;
- Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
- OpsModified = true;
- AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
- if (!AddRec)
- break;
}
+ AddRecOps.push_back(Term);
+ }
+ if (!Overflow) {
+ const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
+ SCEV::FlagAnyWrap);
+ if (Ops.size() == 2) return NewAddRec;
+ Ops[Idx] = NewAddRec;
+ Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
+ OpsModified = true;
+ AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
+ if (!AddRec)
+ break;
}
- if (OpsModified)
- return getMulExpr(Ops);
}
+ if (OpsModified)
+ return getMulExpr(Ops);
// Otherwise couldn't fold anything into this recurrence. Move onto the
// next one.
ID.AddInteger(scMulExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
- void *IP = 0;
+ void *IP = nullptr;
SCEVMulExpr *S =
static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
if (!S) {
ID.AddInteger(scUDivExpr);
ID.AddPointer(LHS);
ID.AddPointer(RHS);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
LHS, RHS);
return S;
}
+static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
+ APInt A = C1->getValue()->getValue().abs();
+ APInt B = C2->getValue()->getValue().abs();
+ uint32_t ABW = A.getBitWidth();
+ uint32_t BBW = B.getBitWidth();
+
+ if (ABW > BBW)
+ B = B.zext(ABW);
+ else if (ABW < BBW)
+ A = A.zext(BBW);
+
+ return APIntOps::GreatestCommonDivisor(A, B);
+}
+
+/// getUDivExactExpr - Get a canonical unsigned division expression, or
+/// something simpler if possible. There is no representation for an exact udiv
+/// in SCEV IR, but we can attempt to remove factors from the LHS and RHS.
+/// We can't do this when it's not exact because the udiv may be clearing bits.
+const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
+ const SCEV *RHS) {
+ // TODO: we could try to find factors in all sorts of things, but for now we
+ // just deal with u/exact (multiply, constant). See SCEVDivision towards the
+ // end of this file for inspiration.
+
+ const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
+ if (!Mul)
+ return getUDivExpr(LHS, RHS);
+
+ if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
+ // If the mulexpr multiplies by a constant, then that constant must be the
+ // first element of the mulexpr.
+ if (const SCEVConstant *LHSCst =
+ dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
+ if (LHSCst == RHSCst) {
+ SmallVector<const SCEV *, 2> Operands;
+ Operands.append(Mul->op_begin() + 1, Mul->op_end());
+ return getMulExpr(Operands);
+ }
+
+ // We can't just assume that LHSCst divides RHSCst cleanly, it could be
+ // that there's a factor provided by one of the other terms. We need to
+ // check.
+ APInt Factor = gcd(LHSCst, RHSCst);
+ if (!Factor.isIntN(1)) {
+ LHSCst = cast<SCEVConstant>(
+ getConstant(LHSCst->getValue()->getValue().udiv(Factor)));
+ RHSCst = cast<SCEVConstant>(
+ getConstant(RHSCst->getValue()->getValue().udiv(Factor)));
+ SmallVector<const SCEV *, 2> Operands;
+ Operands.push_back(LHSCst);
+ Operands.append(Mul->op_begin() + 1, Mul->op_end());
+ LHS = getMulExpr(Operands);
+ RHS = RHSCst;
+ Mul = dyn_cast<SCEVMulExpr>(LHS);
+ if (!Mul)
+ return getUDivExactExpr(LHS, RHS);
+ }
+ }
+ }
+
+ for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
+ if (Mul->getOperand(i) == RHS) {
+ SmallVector<const SCEV *, 2> Operands;
+ Operands.append(Mul->op_begin(), Mul->op_begin() + i);
+ Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
+ return getMulExpr(Operands);
+ }
+ }
+
+ return getUDivExpr(LHS, RHS);
+}
/// getAddRecExpr - Get an add recurrence expression for the specified loop.
/// Simplify the expression as much as possible.
for (unsigned i = 0, e = Operands.size(); i != e; ++i)
ID.AddPointer(Operands[i]);
ID.AddPointer(L);
- void *IP = 0;
+ void *IP = nullptr;
SCEVAddRecExpr *S =
static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
if (!S) {
ID.AddInteger(scSMaxExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
std::uninitialized_copy(Ops.begin(), Ops.end(), O);
ID.AddInteger(scUMaxExpr);
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
ID.AddPointer(Ops[i]);
- void *IP = 0;
+ void *IP = nullptr;
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
std::uninitialized_copy(Ops.begin(), Ops.end(), O);
return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
}
-const SCEV *ScalarEvolution::getSizeOfExpr(Type *AllocTy) {
+const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
// If we have DataLayout, we can bypass creating a target-independent
// constant expression and then folding it back into a ConstantInt.
// This is just a compile-time optimization.
- if (TD)
- return getConstant(TD->getIntPtrType(getContext()),
- TD->getTypeAllocSize(AllocTy));
+ if (DL)
+ return getConstant(IntTy, DL->getTypeAllocSize(AllocTy));
Constant *C = ConstantExpr::getSizeOf(AllocTy);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
- if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI))
- C = Folded;
- Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
- return getTruncateOrZeroExtend(getSCEV(C), Ty);
-}
-
-const SCEV *ScalarEvolution::getAlignOfExpr(Type *AllocTy) {
- Constant *C = ConstantExpr::getAlignOf(AllocTy);
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
- if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI))
+ if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
C = Folded;
Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
+ assert(Ty == IntTy && "Effective SCEV type doesn't match");
return getTruncateOrZeroExtend(getSCEV(C), Ty);
}
-const SCEV *ScalarEvolution::getOffsetOfExpr(StructType *STy,
+const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
+ StructType *STy,
unsigned FieldNo) {
// If we have DataLayout, we can bypass creating a target-independent
// constant expression and then folding it back into a ConstantInt.
// This is just a compile-time optimization.
- if (TD)
- return getConstant(TD->getIntPtrType(getContext()),
- TD->getStructLayout(STy)->getElementOffset(FieldNo));
+ if (DL) {
+ return getConstant(IntTy,
+ DL->getStructLayout(STy)->getElementOffset(FieldNo));
+ }
Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
- if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI))
+ if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
C = Folded;
- Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
- return getTruncateOrZeroExtend(getSCEV(C), Ty);
-}
-const SCEV *ScalarEvolution::getOffsetOfExpr(Type *CTy,
- Constant *FieldNo) {
- Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
- if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI))
- C = Folded;
- Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
+ Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
return getTruncateOrZeroExtend(getSCEV(C), Ty);
}
FoldingSetNodeID ID;
ID.AddInteger(scUnknown);
ID.AddPointer(V);
- void *IP = 0;
+ void *IP = nullptr;
if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
assert(cast<SCEVUnknown>(S)->getValue() == V &&
"Stale SCEVUnknown in uniquing map!");
assert(isSCEVable(Ty) && "Type is not SCEVable!");
// If we have a DataLayout, use it!
- if (TD)
- return TD->getTypeSizeInBits(Ty);
+ if (DL)
+ return DL->getTypeSizeInBits(Ty);
// Integer types have fixed sizes.
if (Ty->isIntegerTy())
Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
assert(isSCEVable(Ty) && "Type is not SCEVable!");
- if (Ty->isIntegerTy())
+ if (Ty->isIntegerTy()) {
return Ty;
+ }
// The only other support type is pointer.
assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
- if (TD) return TD->getIntPtrType(getContext());
+
+ if (DL)
+ return DL->getIntPtrType(Ty);
// Without DataLayout, conservatively assume pointers are 64-bit.
return Type::getInt64Ty(getContext());
bool FindOne;
FindInvalidSCEVUnknown() { FindOne = false; }
bool follow(const SCEV *S) {
- switch (S->getSCEVType()) {
+ switch (static_cast<SCEVTypes>(S->getSCEVType())) {
case scConstant:
return false;
case scUnknown:
- if(!cast<SCEVUnknown>(S)->getValue())
+ if (!cast<SCEVUnknown>(S)->getValue())
FindOne = true;
return false;
default:
ValueExprMapType::iterator I = ValueExprMap.find_as(V);
if (I != ValueExprMap.end()) {
const SCEV *S = I->second;
- if(checkValidity(S))
+ if (checkValidity(S))
return S;
else
ValueExprMap.erase(I);
return getPointerBase(Cast->getOperand());
}
else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
- const SCEV *PtrOp = 0;
+ const SCEV *PtrOp = nullptr;
for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
I != E; ++I) {
if ((*I)->getType()->isPointerTy()) {
PushDefUseChildren(Instruction *I,
SmallVectorImpl<Instruction *> &Worklist) {
// Push the def-use children onto the Worklist stack.
- for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
- UI != UE; ++UI)
- Worklist.push_back(cast<Instruction>(*UI));
+ for (User *U : I->users())
+ Worklist.push_back(cast<Instruction>(U));
}
/// ForgetSymbolicValue - This looks up computed SCEV values for all
Visited.insert(PN);
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
- if (!Visited.insert(I)) continue;
+ if (!Visited.insert(I).second)
+ continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
// The loop may have multiple entrances or multiple exits; we can analyze
// this phi as an addrec if it has a unique entry value and a unique
// backedge value.
- Value *BEValueV = 0, *StartValueV = 0;
+ Value *BEValueV = nullptr, *StartValueV = nullptr;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *V = PN->getIncomingValue(i);
if (L->contains(PN->getIncomingBlock(i))) {
if (!BEValueV) {
BEValueV = V;
} else if (BEValueV != V) {
- BEValueV = 0;
+ BEValueV = nullptr;
break;
}
} else if (!StartValueV) {
StartValueV = V;
} else if (StartValueV != V) {
- StartValueV = 0;
+ StartValueV = nullptr;
break;
}
}
Flags = setFlags(Flags, SCEV::FlagNUW);
if (OBO->hasNoSignedWrap())
Flags = setFlags(Flags, SCEV::FlagNSW);
- } else if (const GEPOperator *GEP =
- dyn_cast<GEPOperator>(BEValueV)) {
+ } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
// If the increment is an inbounds GEP, then we know the address
// space cannot be wrapped around. We cannot make any guarantee
// about signed or unsigned overflow because pointers are
// unsigned but we may have a negative index from the base
- // pointer.
- if (GEP->isInBounds())
+ // pointer. We can guarantee that no unsigned wrap occurs if the
+ // indices form a positive value.
+ if (GEP->isInBounds()) {
Flags = setFlags(Flags, SCEV::FlagNW);
+
+ const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
+ if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
+ Flags = setFlags(Flags, SCEV::FlagNUW);
+ }
+ } else if (const SubOperator *OBO =
+ dyn_cast<SubOperator>(BEValueV)) {
+ if (OBO->hasNoUnsignedWrap())
+ Flags = setFlags(Flags, SCEV::FlagNUW);
+ if (OBO->hasNoSignedWrap())
+ Flags = setFlags(Flags, SCEV::FlagNSW);
}
const SCEV *StartVal = getSCEV(StartValueV);
// PHI's incoming blocks are in a different loop, in which case doing so
// risks breaking LCSSA form. Instcombine would normally zap these, but
// it doesn't have DominatorTree information, so it may miss cases.
- if (Value *V = SimplifyInstruction(PN, TD, TLI, DT))
+ if (Value *V = SimplifyInstruction(PN, DL, TLI, DT, AT))
if (LI->replacementPreservesLCSSAForm(PN, V))
return getSCEV(V);
/// operations. This allows them to be analyzed by regular SCEV code.
///
const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
+ Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
+ Value *Base = GEP->getOperand(0);
+ // Don't attempt to analyze GEPs over unsized objects.
+ if (!Base->getType()->getPointerElementType()->isSized())
+ return getUnknown(GEP);
// Don't blindly transfer the inbounds flag from the GEP instruction to the
// Add expression, because the Instruction may be guarded by control flow
// and the no-overflow bits may not be valid for the expression in any
// context.
- bool isInBounds = GEP->isInBounds();
+ SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
- Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
- Value *Base = GEP->getOperand(0);
- // Don't attempt to analyze GEPs over unsized objects.
- if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
- return getUnknown(GEP);
const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
gep_type_iterator GTI = gep_type_begin(GEP);
- for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
+ for (GetElementPtrInst::op_iterator I = std::next(GEP->op_begin()),
E = GEP->op_end();
I != E; ++I) {
Value *Index = *I;
if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset.
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
- const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
+ const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
// Add the field offset to the running total offset.
TotalOffset = getAddExpr(TotalOffset, FieldOffset);
} else {
// For an array, add the element offset, explicitly scaled.
- const SCEV *ElementSize = getSizeOfExpr(*GTI);
+ const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, *GTI);
const SCEV *IndexS = getSCEV(Index);
// Getelementptr indices are signed.
IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
// Multiply the index by the element size to compute the element offset.
- const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize,
- isInBounds ? SCEV::FlagNSW :
- SCEV::FlagAnyWrap);
+ const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize, Wrap);
// Add the element offset to the running total offset.
TotalOffset = getAddExpr(TotalOffset, LocalOffset);
const SCEV *BaseS = getSCEV(Base);
// Add the total offset from all the GEP indices to the base.
- return getAddExpr(BaseS, TotalOffset,
- isInBounds ? SCEV::FlagNSW : SCEV::FlagAnyWrap);
+ return getAddExpr(BaseS, TotalOffset, Wrap);
}
/// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
// For a SCEVUnknown, ask ValueTracking.
unsigned BitWidth = getTypeSizeInBits(U->getType());
APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
- ComputeMaskedBits(U->getValue(), Zeros, Ones);
+ computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
return Zeros.countTrailingOnes();
}
return 0;
}
+/// GetRangeFromMetadata - Helper method to assign a range to V from
+/// metadata present in the IR.
+static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
+ if (Instruction *I = dyn_cast<Instruction>(V)) {
+ if (MDNode *MD = I->getMetadata(LLVMContext::MD_range)) {
+ ConstantRange TotalRange(
+ cast<IntegerType>(I->getType())->getBitWidth(), false);
+
+ unsigned NumRanges = MD->getNumOperands() / 2;
+ assert(NumRanges >= 1);
+
+ for (unsigned i = 0; i < NumRanges; ++i) {
+ ConstantInt *Lower =
+ mdconst::extract<ConstantInt>(MD->getOperand(2 * i + 0));
+ ConstantInt *Upper =
+ mdconst::extract<ConstantInt>(MD->getOperand(2 * i + 1));
+ ConstantRange Range(Lower->getValue(), Upper->getValue());
+ TotalRange = TotalRange.unionWith(Range);
+ }
+
+ return TotalRange;
+ }
+ }
+
+ return None;
+}
+
/// getUnsignedRange - Determine the unsigned range for a particular SCEV.
///
ConstantRange
}
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
+ // Check if the IR explicitly contains !range metadata.
+ Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
+ if (MDRange.hasValue())
+ ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
+
// For a SCEVUnknown, ask ValueTracking.
APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
- ComputeMaskedBits(U->getValue(), Zeros, Ones, TD);
+ computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
if (Ones == ~Zeros + 1)
return setUnsignedRange(U, ConservativeResult);
return setUnsignedRange(U,
}
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
+ // Check if the IR explicitly contains !range metadata.
+ Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
+ if (MDRange.hasValue())
+ ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
+
// For a SCEVUnknown, ask ValueTracking.
- if (!U->getValue()->getType()->isIntegerTy() && !TD)
+ if (!U->getValue()->getType()->isIntegerTy() && !DL)
return setSignedRange(U, ConservativeResult);
- unsigned NS = ComputeNumSignBits(U->getValue(), TD);
+ unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, AT, nullptr, DT);
if (NS <= 1)
return setSignedRange(U, ConservativeResult);
return setSignedRange(U, ConservativeResult.intersectWith(
// Instcombine's ShrinkDemandedConstant may strip bits out of
// constants, obscuring what would otherwise be a low-bits mask.
- // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
+ // Use computeKnownBits to compute what ShrinkDemandedConstant
// knew about to reconstruct a low-bits mask value.
unsigned LZ = A.countLeadingZeros();
+ unsigned TZ = A.countTrailingZeros();
unsigned BitWidth = A.getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
- ComputeMaskedBits(U->getOperand(0), KnownZero, KnownOne, TD);
-
- APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
-
- if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
- return
- getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
- IntegerType::get(getContext(), BitWidth - LZ)),
- U->getType());
+ computeKnownBits(U->getOperand(0), KnownZero, KnownOne, DL,
+ 0, AT, nullptr, DT);
+
+ APInt EffectiveMask =
+ APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
+ if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
+ const SCEV *MulCount = getConstant(
+ ConstantInt::get(getContext(), APInt::getOneBitSet(BitWidth, TZ)));
+ return getMulExpr(
+ getZeroExtendExpr(
+ getTruncateExpr(
+ getUDivExactExpr(getSCEV(U->getOperand(0)), MulCount),
+ IntegerType::get(getContext(), BitWidth - LZ - TZ)),
+ U->getType()),
+ MulCount);
+ }
}
break;
// Iteration Count Computation Code
//
+unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
+ if (BasicBlock *ExitingBB = L->getExitingBlock())
+ return getSmallConstantTripCount(L, ExitingBB);
+
+ // No trip count information for multiple exits.
+ return 0;
+}
+
/// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
/// normal unsigned value. Returns 0 if the trip count is unknown or not
/// constant. Will also return 0 if the maximum trip count is very large (>=
/// before taking the branch. For loops with multiple exits, it may not be the
/// number times that the loop header executes because the loop may exit
/// prematurely via another branch.
-///
-/// FIXME: We conservatively call getBackedgeTakenCount(L) instead of
-/// getExitCount(L, ExitingBlock) to compute a safe trip count considering all
-/// loop exits. getExitCount() may return an exact count for this branch
-/// assuming no-signed-wrap. The number of well-defined iterations may actually
-/// be higher than this trip count if this exit test is skipped and the loop
-/// exits via a different branch. Ideally, getExitCount() would know whether it
-/// depends on a NSW assumption, and we would only fall back to a conservative
-/// trip count in that case.
-unsigned ScalarEvolution::
-getSmallConstantTripCount(Loop *L, BasicBlock * /*ExitingBlock*/) {
+unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
+ BasicBlock *ExitingBlock) {
+ assert(ExitingBlock && "Must pass a non-null exiting block!");
+ assert(L->isLoopExiting(ExitingBlock) &&
+ "Exiting block must actually branch out of the loop!");
const SCEVConstant *ExitCount =
- dyn_cast<SCEVConstant>(getBackedgeTakenCount(L));
+ dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
if (!ExitCount)
return 0;
return ((unsigned)ExitConst->getZExtValue()) + 1;
}
+unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
+ if (BasicBlock *ExitingBB = L->getExitingBlock())
+ return getSmallConstantTripMultiple(L, ExitingBB);
+
+ // No trip multiple information for multiple exits.
+ return 0;
+}
+
/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
/// trip count of this loop as a normal unsigned value, if possible. This
/// means that the actual trip count is always a multiple of the returned
///
/// As explained in the comments for getSmallConstantTripCount, this assumes
/// that control exits the loop via ExitingBlock.
-unsigned ScalarEvolution::
-getSmallConstantTripMultiple(Loop *L, BasicBlock * /*ExitingBlock*/) {
- const SCEV *ExitCount = getBackedgeTakenCount(L);
+unsigned
+ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
+ BasicBlock *ExitingBlock) {
+ assert(ExitingBlock && "Must pass a non-null exiting block!");
+ assert(L->isLoopExiting(ExitingBlock) &&
+ "Exiting block must actually branch out of the loop!");
+ const SCEV *ExitCount = getExitCount(L, ExitingBlock);
if (ExitCount == getCouldNotCompute())
return 1;
SmallPtrSet<Instruction *, 8> Visited;
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
- if (!Visited.insert(I)) continue;
+ if (!Visited.insert(I).second)
+ continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
SmallPtrSet<Instruction *, 8> Visited;
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
- if (!Visited.insert(I)) continue;
+ if (!Visited.insert(I).second)
+ continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
SmallPtrSet<Instruction *, 8> Visited;
while (!Worklist.empty()) {
I = Worklist.pop_back_val();
- if (!Visited.insert(I)) continue;
+ if (!Visited.insert(I).second)
+ continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
- const SCEV *BECount = 0;
+ const SCEV *BECount = nullptr;
for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
- ENT != 0; ENT = ENT->getNextExit()) {
+ ENT != nullptr; ENT = ENT->getNextExit()) {
assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
ScalarEvolution *SE) const {
for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
- ENT != 0; ENT = ENT->getNextExit()) {
+ ENT != nullptr; ENT = ENT->getNextExit()) {
if (ENT->ExitingBlock == ExitingBlock)
return ENT->ExactNotTaken;
return false;
for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
- ENT != 0; ENT = ENT->getNextExit()) {
+ ENT != nullptr; ENT = ENT->getNextExit()) {
if (ENT->ExactNotTaken != SE->getCouldNotCompute()
&& SE->hasOperand(ENT->ExactNotTaken, S)) {
/// clear - Invalidate this result and free the ExitNotTakenInfo array.
void ScalarEvolution::BackedgeTakenInfo::clear() {
- ExitNotTaken.ExitingBlock = 0;
- ExitNotTaken.ExactNotTaken = 0;
+ ExitNotTaken.ExitingBlock = nullptr;
+ ExitNotTaken.ExactNotTaken = nullptr;
delete[] ExitNotTaken.getNextExit();
}
SmallVector<BasicBlock *, 8> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
- // Examine all exits and pick the most conservative values.
- const SCEV *MaxBECount = getCouldNotCompute();
- bool CouldComputeBECount = true;
SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
+ bool CouldComputeBECount = true;
+ BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
+ const SCEV *MustExitMaxBECount = nullptr;
+ const SCEV *MayExitMaxBECount = nullptr;
+
+ // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
+ // and compute maxBECount.
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
- ExitLimit EL = ComputeExitLimit(L, ExitingBlocks[i]);
+ BasicBlock *ExitBB = ExitingBlocks[i];
+ ExitLimit EL = ComputeExitLimit(L, ExitBB);
+
+ // 1. For each exit that can be computed, add an entry to ExitCounts.
+ // CouldComputeBECount is true only if all exits can be computed.
if (EL.Exact == getCouldNotCompute())
// We couldn't compute an exact value for this exit, so
// we won't be able to compute an exact value for the loop.
CouldComputeBECount = false;
else
- ExitCounts.push_back(std::make_pair(ExitingBlocks[i], EL.Exact));
+ ExitCounts.push_back(std::make_pair(ExitBB, EL.Exact));
- if (MaxBECount == getCouldNotCompute())
- MaxBECount = EL.Max;
- else if (EL.Max != getCouldNotCompute()) {
- // We cannot take the "min" MaxBECount, because non-unit stride loops may
- // skip some loop tests. Taking the max over the exits is sufficiently
- // conservative. TODO: We could do better taking into consideration
- // that (1) the loop has unit stride (2) the last loop test is
- // less-than/greater-than (3) any loop test is less-than/greater-than AND
- // falls-through some constant times less then the other tests.
- MaxBECount = getUMaxFromMismatchedTypes(MaxBECount, EL.Max);
+ // 2. Derive the loop's MaxBECount from each exit's max number of
+ // non-exiting iterations. Partition the loop exits into two kinds:
+ // LoopMustExits and LoopMayExits.
+ //
+ // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
+ // is a LoopMayExit. If any computable LoopMustExit is found, then
+ // MaxBECount is the minimum EL.Max of computable LoopMustExits. Otherwise,
+ // MaxBECount is conservatively the maximum EL.Max, where CouldNotCompute is
+ // considered greater than any computable EL.Max.
+ if (EL.Max != getCouldNotCompute() && Latch &&
+ DT->dominates(ExitBB, Latch)) {
+ if (!MustExitMaxBECount)
+ MustExitMaxBECount = EL.Max;
+ else {
+ MustExitMaxBECount =
+ getUMinFromMismatchedTypes(MustExitMaxBECount, EL.Max);
+ }
+ } else if (MayExitMaxBECount != getCouldNotCompute()) {
+ if (!MayExitMaxBECount || EL.Max == getCouldNotCompute())
+ MayExitMaxBECount = EL.Max;
+ else {
+ MayExitMaxBECount =
+ getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.Max);
+ }
}
}
-
+ const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
+ (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
}
ScalarEvolution::ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
// Okay, we've chosen an exiting block. See what condition causes us to
- // exit at this block.
- //
- // FIXME: we should be able to handle switch instructions (with a single exit)
- BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
- if (ExitBr == 0) return getCouldNotCompute();
- assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
+ // exit at this block and remember the exit block and whether all other targets
+ // lead to the loop header.
+ bool MustExecuteLoopHeader = true;
+ BasicBlock *Exit = nullptr;
+ for (succ_iterator SI = succ_begin(ExitingBlock), SE = succ_end(ExitingBlock);
+ SI != SE; ++SI)
+ if (!L->contains(*SI)) {
+ if (Exit) // Multiple exit successors.
+ return getCouldNotCompute();
+ Exit = *SI;
+ } else if (*SI != L->getHeader()) {
+ MustExecuteLoopHeader = false;
+ }
// At this point, we know we have a conditional branch that determines whether
// the loop is exited. However, we don't know if the branch is executed each
//
// More extensive analysis could be done to handle more cases here.
//
- if (ExitBr->getSuccessor(0) != L->getHeader() &&
- ExitBr->getSuccessor(1) != L->getHeader() &&
- ExitBr->getParent() != L->getHeader()) {
+ if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
// The simple checks failed, try climbing the unique predecessor chain
// up to the header.
bool Ok = false;
- for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
+ for (BasicBlock *BB = ExitingBlock; BB; ) {
BasicBlock *Pred = BB->getUniquePredecessor();
if (!Pred)
return getCouldNotCompute();
return getCouldNotCompute();
}
- // Proceed to the next level to examine the exit condition expression.
- return ComputeExitLimitFromCond(L, ExitBr->getCondition(),
- ExitBr->getSuccessor(0),
- ExitBr->getSuccessor(1),
- /*IsSubExpr=*/false);
+ bool IsOnlyExit = (L->getExitingBlock() != nullptr);
+ TerminatorInst *Term = ExitingBlock->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
+ assert(BI->isConditional() && "If unconditional, it can't be in loop!");
+ // Proceed to the next level to examine the exit condition expression.
+ return ComputeExitLimitFromCond(L, BI->getCondition(), BI->getSuccessor(0),
+ BI->getSuccessor(1),
+ /*ControlsExit=*/IsOnlyExit);
+ }
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
+ return ComputeExitLimitFromSingleExitSwitch(L, SI, Exit,
+ /*ControlsExit=*/IsOnlyExit);
+
+ return getCouldNotCompute();
}
/// ComputeExitLimitFromCond - Compute the number of times the
/// backedge of the specified loop will execute if its exit condition
/// were a conditional branch of ExitCond, TBB, and FBB.
///
-/// @param IsSubExpr is true if ExitCond does not directly control the exit
-/// branch. In this case, we cannot assume that the loop only exits when the
-/// condition is true and cannot infer that failing to meet the condition prior
-/// to integer wraparound results in undefined behavior.
+/// @param ControlsExit is true if ExitCond directly controls the exit
+/// branch. In this case, we can assume that the loop exits only if the
+/// condition is true and can infer that failing to meet the condition prior to
+/// integer wraparound results in undefined behavior.
ScalarEvolution::ExitLimit
ScalarEvolution::ComputeExitLimitFromCond(const Loop *L,
Value *ExitCond,
BasicBlock *TBB,
BasicBlock *FBB,
- bool IsSubExpr) {
+ bool ControlsExit) {
// Check if the controlling expression for this loop is an And or Or.
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
if (BO->getOpcode() == Instruction::And) {
// Recurse on the operands of the and.
bool EitherMayExit = L->contains(TBB);
ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
- IsSubExpr || EitherMayExit);
+ ControlsExit && !EitherMayExit);
ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
- IsSubExpr || EitherMayExit);
+ ControlsExit && !EitherMayExit);
const SCEV *BECount = getCouldNotCompute();
const SCEV *MaxBECount = getCouldNotCompute();
if (EitherMayExit) {
// Recurse on the operands of the or.
bool EitherMayExit = L->contains(FBB);
ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
- IsSubExpr || EitherMayExit);
+ ControlsExit && !EitherMayExit);
ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
- IsSubExpr || EitherMayExit);
+ ControlsExit && !EitherMayExit);
const SCEV *BECount = getCouldNotCompute();
const SCEV *MaxBECount = getCouldNotCompute();
if (EitherMayExit) {
// With an icmp, it may be feasible to compute an exact backedge-taken count.
// Proceed to the next level to examine the icmp.
if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
- return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, IsSubExpr);
+ return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
// Check for a constant condition. These are normally stripped out by
// SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
ICmpInst *ExitCond,
BasicBlock *TBB,
BasicBlock *FBB,
- bool IsSubExpr) {
+ bool ControlsExit) {
// If the condition was exit on true, convert the condition to exit on false
ICmpInst::Predicate Cond;
switch (Cond) {
case ICmpInst::ICMP_NE: { // while (X != Y)
// Convert to: while (X-Y != 0)
- ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, IsSubExpr);
+ ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
if (EL.hasAnyInfo()) return EL;
break;
}
if (EL.hasAnyInfo()) return EL;
break;
}
- case ICmpInst::ICMP_SLT: {
- ExitLimit EL = HowManyLessThans(LHS, RHS, L, true, IsSubExpr);
- if (EL.hasAnyInfo()) return EL;
- break;
- }
- case ICmpInst::ICMP_SGT: {
- ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
- getNotSCEV(RHS), L, true, IsSubExpr);
- if (EL.hasAnyInfo()) return EL;
- break;
- }
- case ICmpInst::ICMP_ULT: {
- ExitLimit EL = HowManyLessThans(LHS, RHS, L, false, IsSubExpr);
+ case ICmpInst::ICMP_SLT:
+ case ICmpInst::ICMP_ULT: { // while (X < Y)
+ bool IsSigned = Cond == ICmpInst::ICMP_SLT;
+ ExitLimit EL = HowManyLessThans(LHS, RHS, L, IsSigned, ControlsExit);
if (EL.hasAnyInfo()) return EL;
break;
}
- case ICmpInst::ICMP_UGT: {
- ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
- getNotSCEV(RHS), L, false, IsSubExpr);
+ case ICmpInst::ICMP_SGT:
+ case ICmpInst::ICMP_UGT: { // while (X > Y)
+ bool IsSigned = Cond == ICmpInst::ICMP_SGT;
+ ExitLimit EL = HowManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit);
if (EL.hasAnyInfo()) return EL;
break;
}
return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
}
+ScalarEvolution::ExitLimit
+ScalarEvolution::ComputeExitLimitFromSingleExitSwitch(const Loop *L,
+ SwitchInst *Switch,
+ BasicBlock *ExitingBlock,
+ bool ControlsExit) {
+ assert(!L->contains(ExitingBlock) && "Not an exiting block!");
+
+ // Give up if the exit is the default dest of a switch.
+ if (Switch->getDefaultDest() == ExitingBlock)
+ return getCouldNotCompute();
+
+ assert(L->contains(Switch->getDefaultDest()) &&
+ "Default case must not exit the loop!");
+ const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
+ const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
+
+ // while (X != Y) --> while (X-Y != 0)
+ ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
+ if (EL.hasAnyInfo())
+ return EL;
+
+ return getCouldNotCompute();
+}
+
static ConstantInt *
EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
ScalarEvolution &SE) {
return getCouldNotCompute();
// Okay, we allow one non-constant index into the GEP instruction.
- Value *VarIdx = 0;
+ Value *VarIdx = nullptr;
std::vector<Constant*> Indexes;
unsigned VarIdxNum = 0;
for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
VarIdx = GEP->getOperand(i);
VarIdxNum = i-2;
- Indexes.push_back(0);
+ Indexes.push_back(nullptr);
}
// Loop-invariant loads may be a byproduct of loop optimization. Skip them.
Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
Indexes);
- if (Result == 0) break; // Cannot compute!
+ if (!Result) break; // Cannot compute!
// Evaluate the condition for this iteration.
Result = ConstantExpr::getICmp(predicate, Result, RHS);
// Otherwise, we can evaluate this instruction if all of its operands are
// constant or derived from a PHI node themselves.
- PHINode *PHI = 0;
+ PHINode *PHI = nullptr;
for (Instruction::op_iterator OpI = UseInst->op_begin(),
OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
if (isa<Constant>(*OpI)) continue;
Instruction *OpInst = dyn_cast<Instruction>(*OpI);
- if (!OpInst || !canConstantEvolve(OpInst, L)) return 0;
+ if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
PHINode *P = dyn_cast<PHINode>(OpInst);
if (!P)
P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
PHIMap[OpInst] = P;
}
- if (P == 0) return 0; // Not evolving from PHI
- if (PHI && PHI != P) return 0; // Evolving from multiple different PHIs.
+ if (!P)
+ return nullptr; // Not evolving from PHI
+ if (PHI && PHI != P)
+ return nullptr; // Evolving from multiple different PHIs.
PHI = P;
}
// This is a expression evolving from a constant PHI!
/// constraints, return null.
static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
Instruction *I = dyn_cast<Instruction>(V);
- if (I == 0 || !canConstantEvolve(I, L)) return 0;
+ if (!I || !canConstantEvolve(I, L)) return nullptr;
if (PHINode *PN = dyn_cast<PHINode>(I)) {
return PN;
/// reason, return null.
static Constant *EvaluateExpression(Value *V, const Loop *L,
DenseMap<Instruction *, Constant *> &Vals,
- const DataLayout *TD,
+ const DataLayout *DL,
const TargetLibraryInfo *TLI) {
// Convenient constant check, but redundant for recursive calls.
if (Constant *C = dyn_cast<Constant>(V)) return C;
Instruction *I = dyn_cast<Instruction>(V);
- if (!I) return 0;
+ if (!I) return nullptr;
if (Constant *C = Vals.lookup(I)) return C;
// An instruction inside the loop depends on a value outside the loop that we
// weren't given a mapping for, or a value such as a call inside the loop.
- if (!canConstantEvolve(I, L)) return 0;
+ if (!canConstantEvolve(I, L)) return nullptr;
// An unmapped PHI can be due to a branch or another loop inside this loop,
// or due to this not being the initial iteration through a loop where we
// couldn't compute the evolution of this particular PHI last time.
- if (isa<PHINode>(I)) return 0;
+ if (isa<PHINode>(I)) return nullptr;
std::vector<Constant*> Operands(I->getNumOperands());
Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
if (!Operand) {
Operands[i] = dyn_cast<Constant>(I->getOperand(i));
- if (!Operands[i]) return 0;
+ if (!Operands[i]) return nullptr;
continue;
}
- Constant *C = EvaluateExpression(Operand, L, Vals, TD, TLI);
+ Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
Vals[Operand] = C;
- if (!C) return 0;
+ if (!C) return nullptr;
Operands[i] = C;
}
if (CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
- Operands[1], TD, TLI);
+ Operands[1], DL, TLI);
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!LI->isVolatile())
- return ConstantFoldLoadFromConstPtr(Operands[0], TD);
+ return ConstantFoldLoadFromConstPtr(Operands[0], DL);
}
- return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, TD,
+ return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, DL,
TLI);
}
return I->second;
if (BEs.ugt(MaxBruteForceIterations))
- return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
+ return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
// entry must be a constant (coming in from outside of the loop), and the
// second must be derived from the same PHI.
bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
- PHINode *PHI = 0;
+ PHINode *PHI = nullptr;
for (BasicBlock::iterator I = Header->begin();
(PHI = dyn_cast<PHINode>(I)); ++I) {
Constant *StartCST =
dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
- if (StartCST == 0) continue;
+ if (!StartCST) continue;
CurrentIterVals[PHI] = StartCST;
}
if (!CurrentIterVals.count(PN))
- return RetVal = 0;
+ return RetVal = nullptr;
Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
// Execute the loop symbolically to determine the exit value.
if (BEs.getActiveBits() >= 32)
- return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
+ return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
unsigned NumIterations = BEs.getZExtValue(); // must be in range
unsigned IterationNum = 0;
// Compute the value of the PHIs for the next iteration.
// EvaluateExpression adds non-phi values to the CurrentIterVals map.
DenseMap<Instruction *, Constant *> NextIterVals;
- Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD,
+ Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL,
TLI);
- if (NextPHI == 0)
- return 0; // Couldn't evaluate!
+ if (!NextPHI)
+ return nullptr; // Couldn't evaluate!
NextIterVals[PN] = NextPHI;
bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
Constant *&NextPHI = NextIterVals[PHI];
if (!NextPHI) { // Not already computed.
Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
- NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD, TLI);
+ NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
}
if (NextPHI != I->second)
StoppedEvolving = false;
Value *Cond,
bool ExitWhen) {
PHINode *PN = getConstantEvolvingPHI(Cond, L);
- if (PN == 0) return getCouldNotCompute();
+ if (!PN) return getCouldNotCompute();
// If the loop is canonicalized, the PHI will have exactly two entries.
// That's the only form we support here.
// One entry must be a constant (coming in from outside of the loop), and the
// second must be derived from the same PHI.
bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
- PHINode *PHI = 0;
+ PHINode *PHI = nullptr;
for (BasicBlock::iterator I = Header->begin();
(PHI = dyn_cast<PHINode>(I)); ++I) {
Constant *StartCST =
dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
- if (StartCST == 0) continue;
+ if (!StartCST) continue;
CurrentIterVals[PHI] = StartCST;
}
if (!CurrentIterVals.count(PN))
for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
ConstantInt *CondVal =
dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L, CurrentIterVals,
- TD, TLI));
+ DL, TLI));
// Couldn't symbolically evaluate.
if (!CondVal) return getCouldNotCompute();
if (NextPHI) continue; // Already computed!
Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
- NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD, TLI);
+ NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
}
CurrentIterVals.swap(NextIterVals);
}
/// original value V is returned.
const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
// Check to see if we've folded this expression at this loop before.
- std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
- std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
- Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
- if (!Pair.second)
- return Pair.first->second ? Pair.first->second : V;
-
+ SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = ValuesAtScopes[V];
+ for (unsigned u = 0; u < Values.size(); u++) {
+ if (Values[u].first == L)
+ return Values[u].second ? Values[u].second : V;
+ }
+ Values.push_back(std::make_pair(L, static_cast<const SCEV *>(nullptr)));
// Otherwise compute it.
const SCEV *C = computeSCEVAtScope(V, L);
- ValuesAtScopes[V][L] = C;
+ SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values2 = ValuesAtScopes[V];
+ for (unsigned u = Values2.size(); u > 0; u--) {
+ if (Values2[u - 1].first == L) {
+ Values2[u - 1].second = C;
+ break;
+ }
+ }
return C;
}
/// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
/// Returns NULL if the SCEV isn't representable as a Constant.
static Constant *BuildConstantFromSCEV(const SCEV *V) {
- switch (V->getSCEVType()) {
- default: // TODO: smax, umax.
+ switch (static_cast<SCEVTypes>(V->getSCEVType())) {
case scCouldNotCompute:
case scAddRecExpr:
break;
case scAddExpr: {
const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
- if (C->getType()->isPointerTy())
- C = ConstantExpr::getBitCast(C, Type::getInt8PtrTy(C->getContext()));
+ if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
+ unsigned AS = PTy->getAddressSpace();
+ Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
+ C = ConstantExpr::getBitCast(C, DestPtrTy);
+ }
for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
- if (!C2) return 0;
+ if (!C2) return nullptr;
// First pointer!
if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
+ unsigned AS = C2->getType()->getPointerAddressSpace();
std::swap(C, C2);
+ Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
// The offsets have been converted to bytes. We can add bytes to an
// i8* by GEP with the byte count in the first index.
- C = ConstantExpr::getBitCast(C,Type::getInt8PtrTy(C->getContext()));
+ C = ConstantExpr::getBitCast(C, DestPtrTy);
}
// Don't bother trying to sum two pointers. We probably can't
// statically compute a load that results from it anyway.
if (C2->getType()->isPointerTy())
- return 0;
+ return nullptr;
- if (C->getType()->isPointerTy()) {
- if (cast<PointerType>(C->getType())->getElementType()->isStructTy())
+ if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
+ if (PTy->getElementType()->isStructTy())
C2 = ConstantExpr::getIntegerCast(
C2, Type::getInt32Ty(C->getContext()), true);
C = ConstantExpr::getGetElementPtr(C, C2);
const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
// Don't bother with pointers at all.
- if (C->getType()->isPointerTy()) return 0;
+ if (C->getType()->isPointerTy()) return nullptr;
for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
- if (!C2 || C2->getType()->isPointerTy()) return 0;
+ if (!C2 || C2->getType()->isPointerTy()) return nullptr;
C = ConstantExpr::getMul(C, C2);
}
return C;
return ConstantExpr::getUDiv(LHS, RHS);
break;
}
+ case scSMaxExpr:
+ case scUMaxExpr:
+ break; // TODO: smax, umax.
}
- return 0;
+ return nullptr;
}
const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
// Check to see if getSCEVAtScope actually made an improvement.
if (MadeImprovement) {
- Constant *C = 0;
+ Constant *C = nullptr;
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
C = ConstantFoldCompareInstOperands(CI->getPredicate(),
- Operands[0], Operands[1], TD,
+ Operands[0], Operands[1], DL,
TLI);
else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!LI->isVolatile())
- C = ConstantFoldLoadFromConstPtr(Operands[0], TD);
+ C = ConstantFoldLoadFromConstPtr(Operands[0], DL);
} else
C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
- Operands, TD, TLI);
+ Operands, DL, TLI);
if (!C) return V;
return getSCEV(C);
}
/// effectively V != 0. We know and take advantage of the fact that this
/// expression only being used in a comparison by zero context.
ScalarEvolution::ExitLimit
-ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool IsSubExpr) {
+ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool ControlsExit) {
// If the value is a constant
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
// If the value is already zero, the branch will execute zero times.
// to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
// We have not yet seen any such cases.
const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
- if (StepC == 0 || StepC->getValue()->equalsInt(0))
+ if (!StepC || StepC->getValue()->equalsInt(0))
return getCouldNotCompute();
// For positive steps (counting up until unsigned overflow):
return ExitLimit(Distance, MaxBECount);
}
- // If the recurrence is known not to wraparound, unsigned divide computes the
- // back edge count. (Ideally we would have an "isexact" bit for udiv). We know
- // that the value will either become zero (and thus the loop terminates), that
- // the loop will terminate through some other exit condition first, or that
- // the loop has undefined behavior. This means we can't "miss" the exit
- // value, even with nonunit stride.
- //
- // This is only valid for expressions that directly compute the loop exit. It
- // is invalid for subexpressions in which the loop may exit through this
- // branch even if this subexpression is false. In that case, the trip count
- // computed by this udiv could be smaller than the number of well-defined
- // iterations.
- if (!IsSubExpr && AddRec->getNoWrapFlags(SCEV::FlagNW))
- return getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
+ // If the step exactly divides the distance then unsigned divide computes the
+ // backedge count.
+ const SCEV *Q, *R;
+ ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
+ SCEVUDivision::divide(SE, Distance, Step, &Q, &R);
+ if (R->isZero()) {
+ const SCEV *Exact =
+ getUDivExactExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
+ return ExitLimit(Exact, Exact);
+ }
+
+ // If the condition controls loop exit (the loop exits only if the expression
+ // is true) and the addition is no-wrap we can use unsigned divide to
+ // compute the backedge count. In this case, the step may not divide the
+ // distance, but we don't care because if the condition is "missed" the loop
+ // will have undefined behavior due to wrapping.
+ if (ControlsExit && AddRec->getNoWrapFlags(SCEV::FlagNW)) {
+ const SCEV *Exact =
+ getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
+ return ExitLimit(Exact, Exact);
+ }
// Then, try to solve the above equation provided that Start is constant.
if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
// If LHS or RHS is an addrec, check to see if the condition is true in
// every iteration of the loop.
- if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
- if (isLoopEntryGuardedByCond(
- AR->getLoop(), Pred, AR->getStart(), RHS) &&
- isLoopBackedgeGuardedByCond(
- AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
- return true;
- if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
- if (isLoopEntryGuardedByCond(
- AR->getLoop(), Pred, LHS, AR->getStart()) &&
- isLoopBackedgeGuardedByCond(
- AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
- return true;
+ // If LHS and RHS are both addrec, both conditions must be true in
+ // every iteration of the loop.
+ const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
+ const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
+ bool LeftGuarded = false;
+ bool RightGuarded = false;
+ if (LAR) {
+ const Loop *L = LAR->getLoop();
+ if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
+ isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
+ if (!RAR) return true;
+ LeftGuarded = true;
+ }
+ }
+ if (RAR) {
+ const Loop *L = RAR->getLoop();
+ if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
+ isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
+ if (!LAR) return true;
+ RightGuarded = true;
+ }
+ }
+ if (LeftGuarded && RightGuarded)
+ return true;
// Otherwise see what can be done with known constant ranges.
return isKnownPredicateWithRanges(Pred, LHS, RHS);
default:
llvm_unreachable("Unexpected ICmpInst::Predicate value!");
case ICmpInst::ICMP_SGT:
- Pred = ICmpInst::ICMP_SLT;
std::swap(LHS, RHS);
case ICmpInst::ICMP_SLT: {
ConstantRange LHSRange = getSignedRange(LHS);
break;
}
case ICmpInst::ICMP_SGE:
- Pred = ICmpInst::ICMP_SLE;
std::swap(LHS, RHS);
case ICmpInst::ICMP_SLE: {
ConstantRange LHSRange = getSignedRange(LHS);
break;
}
case ICmpInst::ICMP_UGT:
- Pred = ICmpInst::ICMP_ULT;
std::swap(LHS, RHS);
case ICmpInst::ICMP_ULT: {
ConstantRange LHSRange = getUnsignedRange(LHS);
break;
}
case ICmpInst::ICMP_UGE:
- Pred = ICmpInst::ICMP_ULE;
std::swap(LHS, RHS);
case ICmpInst::ICMP_ULE: {
ConstantRange LHSRange = getUnsignedRange(LHS);
// (interprocedural conditions notwithstanding).
if (!L) return true;
+ if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
+
BasicBlock *Latch = L->getLoopLatch();
if (!Latch)
return false;
BranchInst *LoopContinuePredicate =
dyn_cast<BranchInst>(Latch->getTerminator());
- if (!LoopContinuePredicate ||
- LoopContinuePredicate->isUnconditional())
- return false;
+ if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
+ isImpliedCond(Pred, LHS, RHS,
+ LoopContinuePredicate->getCondition(),
+ LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
+ return true;
- return isImpliedCond(Pred, LHS, RHS,
- LoopContinuePredicate->getCondition(),
- LoopContinuePredicate->getSuccessor(0) != L->getHeader());
+ // Check conditions due to any @llvm.assume intrinsics.
+ for (auto &CI : AT->assumptions(F)) {
+ if (!DT->dominates(CI, Latch->getTerminator()))
+ continue;
+
+ if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
+ return true;
+ }
+
+ return false;
}
/// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
// (interprocedural conditions notwithstanding).
if (!L) return false;
+ if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
+
// Starting at the loop predecessor, climb up the predecessor chain, as long
// as there are predecessors that can be found that have unique successors
// leading to the original header.
return true;
}
+ // Check conditions due to any @llvm.assume intrinsics.
+ for (auto &CI : AT->assumptions(F)) {
+ if (!DT->dominates(CI, L->getHeader()))
+ continue;
+
+ if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
+ return true;
+ }
+
return false;
}
// LHS' type is checked for above.
if (getTypeSizeInBits(LHS->getType()) >
getTypeSizeInBits(FoundLHS->getType())) {
- if (CmpInst::isSigned(Pred)) {
+ if (CmpInst::isSigned(FoundPred)) {
FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
} else {
RHS, LHS, FoundLHS, FoundRHS);
}
+ // Check if we can make progress by sharpening ranges.
+ if (FoundPred == ICmpInst::ICMP_NE &&
+ (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
+
+ const SCEVConstant *C = nullptr;
+ const SCEV *V = nullptr;
+
+ if (isa<SCEVConstant>(FoundLHS)) {
+ C = cast<SCEVConstant>(FoundLHS);
+ V = FoundRHS;
+ } else {
+ C = cast<SCEVConstant>(FoundRHS);
+ V = FoundLHS;
+ }
+
+ // The guarding predicate tells us that C != V. If the known range
+ // of V is [C, t), we can sharpen the range to [C + 1, t). The
+ // range we consider has to correspond to same signedness as the
+ // predicate we're interested in folding.
+
+ APInt Min = ICmpInst::isSigned(Pred) ?
+ getSignedRange(V).getSignedMin() : getUnsignedRange(V).getUnsignedMin();
+
+ if (Min == C->getValue()->getValue()) {
+ // Given (V >= Min && V != Min) we conclude V >= (Min + 1).
+ // This is true even if (Min + 1) wraps around -- in case of
+ // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)).
+
+ APInt SharperMin = Min + 1;
+
+ switch (Pred) {
+ case ICmpInst::ICMP_SGE:
+ case ICmpInst::ICMP_UGE:
+ // We know V `Pred` SharperMin. If this implies LHS `Pred`
+ // RHS, we're done.
+ if (isImpliedCondOperands(Pred, LHS, RHS, V,
+ getConstant(SharperMin)))
+ return true;
+
+ case ICmpInst::ICMP_SGT:
+ case ICmpInst::ICMP_UGT:
+ // We know from the range information that (V `Pred` Min ||
+ // V == Min). We know from the guarding condition that !(V
+ // == Min). This gives us
+ //
+ // V `Pred` Min || V == Min && !(V == Min)
+ // => V `Pred` Min
+ //
+ // If V `Pred` Min implies LHS `Pred` RHS, we're done.
+
+ if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
+ return true;
+
+ default:
+ // No change
+ break;
+ }
+ }
+ }
+
// Check whether the actual condition is beyond sufficient.
if (FoundPred == ICmpInst::ICMP_EQ)
if (ICmpInst::isTrueWhenEqual(Pred))
return false;
}
-/// getBECount - Subtract the end and start values and divide by the step,
-/// rounding up, to get the number of times the backedge is executed. Return
-/// CouldNotCompute if an intermediate computation overflows.
-const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
- const SCEV *End,
- const SCEV *Step,
- bool NoWrap) {
- assert(!isKnownNegative(Step) &&
- "This code doesn't handle negative strides yet!");
-
- Type *Ty = Start->getType();
-
- // When Start == End, we have an exact BECount == 0. Short-circuit this case
- // here because SCEV may not be able to determine that the unsigned division
- // after rounding is zero.
- if (Start == End)
- return getConstant(Ty, 0);
-
- const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
- const SCEV *Diff = getMinusSCEV(End, Start);
- const SCEV *RoundUp = getAddExpr(Step, NegOne);
-
- // Add an adjustment to the difference between End and Start so that
- // the division will effectively round up.
- const SCEV *Add = getAddExpr(Diff, RoundUp);
-
- if (!NoWrap) {
- // Check Add for unsigned overflow.
- // TODO: More sophisticated things could be done here.
- Type *WideTy = IntegerType::get(getContext(),
- getTypeSizeInBits(Ty) + 1);
- const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
- const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
- const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
- if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
- return getCouldNotCompute();
+// Verify if an linear IV with positive stride can overflow when in a
+// less-than comparison, knowing the invariant term of the comparison, the
+// stride and the knowledge of NSW/NUW flags on the recurrence.
+bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
+ bool IsSigned, bool NoWrap) {
+ if (NoWrap) return false;
+
+ unsigned BitWidth = getTypeSizeInBits(RHS->getType());
+ const SCEV *One = getConstant(Stride->getType(), 1);
+
+ if (IsSigned) {
+ APInt MaxRHS = getSignedRange(RHS).getSignedMax();
+ APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
+ APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
+ .getSignedMax();
+
+ // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
+ return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
}
- return getUDivExpr(Add, Step);
+ APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
+ APInt MaxValue = APInt::getMaxValue(BitWidth);
+ APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
+ .getUnsignedMax();
+
+ // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
+ return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
+}
+
+// Verify if an linear IV with negative stride can overflow when in a
+// greater-than comparison, knowing the invariant term of the comparison,
+// the stride and the knowledge of NSW/NUW flags on the recurrence.
+bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
+ bool IsSigned, bool NoWrap) {
+ if (NoWrap) return false;
+
+ unsigned BitWidth = getTypeSizeInBits(RHS->getType());
+ const SCEV *One = getConstant(Stride->getType(), 1);
+
+ if (IsSigned) {
+ APInt MinRHS = getSignedRange(RHS).getSignedMin();
+ APInt MinValue = APInt::getSignedMinValue(BitWidth);
+ APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
+ .getSignedMax();
+
+ // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
+ return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
+ }
+
+ APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
+ APInt MinValue = APInt::getMinValue(BitWidth);
+ APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
+ .getUnsignedMax();
+
+ // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
+ return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
+}
+
+// Compute the backedge taken count knowing the interval difference, the
+// stride and presence of the equality in the comparison.
+const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
+ bool Equality) {
+ const SCEV *One = getConstant(Step->getType(), 1);
+ Delta = Equality ? getAddExpr(Delta, Step)
+ : getAddExpr(Delta, getMinusSCEV(Step, One));
+ return getUDivExpr(Delta, Step);
}
/// HowManyLessThans - Return the number of times a backedge containing the
/// specified less-than comparison will execute. If not computable, return
/// CouldNotCompute.
///
-/// @param IsSubExpr is true when the LHS < RHS condition does not directly
-/// control the branch. In this case, we can only compute an iteration count for
-/// a subexpression that cannot overflow before evaluating true.
+/// @param ControlsExit is true when the LHS < RHS condition directly controls
+/// the branch (loops exits only if condition is true). In this case, we can use
+/// NoWrapFlags to skip overflow checks.
ScalarEvolution::ExitLimit
ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
- const Loop *L, bool isSigned,
- bool IsSubExpr) {
- // Only handle: "ADDREC < LoopInvariant".
- if (!isLoopInvariant(RHS, L)) return getCouldNotCompute();
+ const Loop *L, bool IsSigned,
+ bool ControlsExit) {
+ // We handle only IV < Invariant
+ if (!isLoopInvariant(RHS, L))
+ return getCouldNotCompute();
- const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
- if (!AddRec || AddRec->getLoop() != L)
+ const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
+
+ // Avoid weird loops
+ if (!IV || IV->getLoop() != L || !IV->isAffine())
return getCouldNotCompute();
- // Check to see if we have a flag which makes analysis easy.
- bool NoWrap = false;
- if (!IsSubExpr) {
- NoWrap = AddRec->getNoWrapFlags(
- (SCEV::NoWrapFlags)(((isSigned ? SCEV::FlagNSW : SCEV::FlagNUW))
- | SCEV::FlagNW));
- }
- if (AddRec->isAffine()) {
- unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
- const SCEV *Step = AddRec->getStepRecurrence(*this);
+ bool NoWrap = ControlsExit &&
+ IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
- if (Step->isZero())
- return getCouldNotCompute();
- if (Step->isOne()) {
- // With unit stride, the iteration never steps past the limit value.
- } else if (isKnownPositive(Step)) {
- // Test whether a positive iteration can step past the limit
- // value and past the maximum value for its type in a single step.
- // Note that it's not sufficient to check NoWrap here, because even
- // though the value after a wrap is undefined, it's not undefined
- // behavior, so if wrap does occur, the loop could either terminate or
- // loop infinitely, but in either case, the loop is guaranteed to
- // iterate at least until the iteration where the wrapping occurs.
- const SCEV *One = getConstant(Step->getType(), 1);
- if (isSigned) {
- APInt Max = APInt::getSignedMaxValue(BitWidth);
- if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
- .slt(getSignedRange(RHS).getSignedMax()))
- return getCouldNotCompute();
- } else {
- APInt Max = APInt::getMaxValue(BitWidth);
- if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
- .ult(getUnsignedRange(RHS).getUnsignedMax()))
- return getCouldNotCompute();
- }
- } else
- // TODO: Handle negative strides here and below.
- return getCouldNotCompute();
+ const SCEV *Stride = IV->getStepRecurrence(*this);
+
+ // Avoid negative or zero stride values
+ if (!isKnownPositive(Stride))
+ return getCouldNotCompute();
+
+ // Avoid proven overflow cases: this will ensure that the backedge taken count
+ // will not generate any unsigned overflow. Relaxed no-overflow conditions
+ // exploit NoWrapFlags, allowing to optimize in presence of undefined
+ // behaviors like the case of C language.
+ if (!Stride->isOne() && doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
+ return getCouldNotCompute();
- // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
- // m. So, we count the number of iterations in which {n,+,s} < m is true.
- // Note that we cannot simply return max(m-n,0)/s because it's not safe to
- // treat m-n as signed nor unsigned due to overflow possibility.
-
- // First, we get the value of the LHS in the first iteration: n
- const SCEV *Start = AddRec->getOperand(0);
-
- // Determine the minimum constant start value.
- const SCEV *MinStart = getConstant(isSigned ?
- getSignedRange(Start).getSignedMin() :
- getUnsignedRange(Start).getUnsignedMin());
-
- // If we know that the condition is true in order to enter the loop,
- // then we know that it will run exactly (m-n)/s times. Otherwise, we
- // only know that it will execute (max(m,n)-n)/s times. In both cases,
- // the division must round up.
- const SCEV *End = RHS;
- if (!isLoopEntryGuardedByCond(L,
- isSigned ? ICmpInst::ICMP_SLT :
- ICmpInst::ICMP_ULT,
- getMinusSCEV(Start, Step), RHS))
- End = isSigned ? getSMaxExpr(RHS, Start)
+ ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
+ : ICmpInst::ICMP_ULT;
+ const SCEV *Start = IV->getStart();
+ const SCEV *End = RHS;
+ if (!isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS)) {
+ const SCEV *Diff = getMinusSCEV(RHS, Start);
+ // If we have NoWrap set, then we can assume that the increment won't
+ // overflow, in which case if RHS - Start is a constant, we don't need to
+ // do a max operation since we can just figure it out statically
+ if (NoWrap && isa<SCEVConstant>(Diff)) {
+ APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
+ if (D.isNegative())
+ End = Start;
+ } else
+ End = IsSigned ? getSMaxExpr(RHS, Start)
: getUMaxExpr(RHS, Start);
+ }
+
+ const SCEV *BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
+
+ APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
+ : getUnsignedRange(Start).getUnsignedMin();
- // Determine the maximum constant end value.
- const SCEV *MaxEnd = getConstant(isSigned ?
- getSignedRange(End).getSignedMax() :
- getUnsignedRange(End).getUnsignedMax());
-
- // If MaxEnd is within a step of the maximum integer value in its type,
- // adjust it down to the minimum value which would produce the same effect.
- // This allows the subsequent ceiling division of (N+(step-1))/step to
- // compute the correct value.
- const SCEV *StepMinusOne = getMinusSCEV(Step,
- getConstant(Step->getType(), 1));
- MaxEnd = isSigned ?
- getSMinExpr(MaxEnd,
- getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
- StepMinusOne)) :
- getUMinExpr(MaxEnd,
- getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
- StepMinusOne));
-
- // Finally, we subtract these two values and divide, rounding up, to get
- // the number of times the backedge is executed.
- const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
-
- // The maximum backedge count is similar, except using the minimum start
- // value and the maximum end value.
- // If we already have an exact constant BECount, use it instead.
- const SCEV *MaxBECount = isa<SCEVConstant>(BECount) ? BECount
- : getBECount(MinStart, MaxEnd, Step, NoWrap);
-
- // If the stride is nonconstant, and NoWrap == true, then
- // getBECount(MinStart, MaxEnd) may not compute. This would result in an
- // exact BECount and invalid MaxBECount, which should be avoided to catch
- // more optimization opportunities.
- if (isa<SCEVCouldNotCompute>(MaxBECount))
- MaxBECount = BECount;
-
- return ExitLimit(BECount, MaxBECount);
+ APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
+ : getUnsignedRange(Stride).getUnsignedMin();
+
+ unsigned BitWidth = getTypeSizeInBits(LHS->getType());
+ APInt Limit = IsSigned ? APInt::getSignedMaxValue(BitWidth) - (MinStride - 1)
+ : APInt::getMaxValue(BitWidth) - (MinStride - 1);
+
+ // Although End can be a MAX expression we estimate MaxEnd considering only
+ // the case End = RHS. This is safe because in the other case (End - Start)
+ // is zero, leading to a zero maximum backedge taken count.
+ APInt MaxEnd =
+ IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
+ : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
+
+ const SCEV *MaxBECount;
+ if (isa<SCEVConstant>(BECount))
+ MaxBECount = BECount;
+ else
+ MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
+ getConstant(MinStride), false);
+
+ if (isa<SCEVCouldNotCompute>(MaxBECount))
+ MaxBECount = BECount;
+
+ return ExitLimit(BECount, MaxBECount);
+}
+
+ScalarEvolution::ExitLimit
+ScalarEvolution::HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
+ const Loop *L, bool IsSigned,
+ bool ControlsExit) {
+ // We handle only IV > Invariant
+ if (!isLoopInvariant(RHS, L))
+ return getCouldNotCompute();
+
+ const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
+
+ // Avoid weird loops
+ if (!IV || IV->getLoop() != L || !IV->isAffine())
+ return getCouldNotCompute();
+
+ bool NoWrap = ControlsExit &&
+ IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
+
+ const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
+
+ // Avoid negative or zero stride values
+ if (!isKnownPositive(Stride))
+ return getCouldNotCompute();
+
+ // Avoid proven overflow cases: this will ensure that the backedge taken count
+ // will not generate any unsigned overflow. Relaxed no-overflow conditions
+ // exploit NoWrapFlags, allowing to optimize in presence of undefined
+ // behaviors like the case of C language.
+ if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
+ return getCouldNotCompute();
+
+ ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
+ : ICmpInst::ICMP_UGT;
+
+ const SCEV *Start = IV->getStart();
+ const SCEV *End = RHS;
+ if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS)) {
+ const SCEV *Diff = getMinusSCEV(RHS, Start);
+ // If we have NoWrap set, then we can assume that the increment won't
+ // overflow, in which case if RHS - Start is a constant, we don't need to
+ // do a max operation since we can just figure it out statically
+ if (NoWrap && isa<SCEVConstant>(Diff)) {
+ APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
+ if (!D.isNegative())
+ End = Start;
+ } else
+ End = IsSigned ? getSMinExpr(RHS, Start)
+ : getUMinExpr(RHS, Start);
}
- return getCouldNotCompute();
+ const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
+
+ APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
+ : getUnsignedRange(Start).getUnsignedMax();
+
+ APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
+ : getUnsignedRange(Stride).getUnsignedMin();
+
+ unsigned BitWidth = getTypeSizeInBits(LHS->getType());
+ APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
+ : APInt::getMinValue(BitWidth) + (MinStride - 1);
+
+ // Although End can be a MIN expression we estimate MinEnd considering only
+ // the case End = RHS. This is safe because in the other case (Start - End)
+ // is zero, leading to a zero maximum backedge taken count.
+ APInt MinEnd =
+ IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
+ : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
+
+
+ const SCEV *MaxBECount = getCouldNotCompute();
+ if (isa<SCEVConstant>(BECount))
+ MaxBECount = BECount;
+ else
+ MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
+ getConstant(MinStride), false);
+
+ if (isa<SCEVCouldNotCompute>(MaxBECount))
+ MaxBECount = BECount;
+
+ return ExitLimit(BECount, MaxBECount);
}
/// getNumIterationsInRange - Return the number of iterations of this loop that
return SE.getCouldNotCompute();
}
+namespace {
+struct FindUndefs {
+ bool Found;
+ FindUndefs() : Found(false) {}
+
+ bool follow(const SCEV *S) {
+ if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
+ if (isa<UndefValue>(C->getValue()))
+ Found = true;
+ } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
+ if (isa<UndefValue>(C->getValue()))
+ Found = true;
+ }
+
+ // Keep looking if we haven't found it yet.
+ return !Found;
+ }
+ bool isDone() const {
+ // Stop recursion if we have found an undef.
+ return Found;
+ }
+};
+}
+
+// Return true when S contains at least an undef value.
+static inline bool
+containsUndefs(const SCEV *S) {
+ FindUndefs F;
+ SCEVTraversal<FindUndefs> ST(F);
+ ST.visitAll(S);
+
+ return F.Found;
+}
+
+namespace {
+// Collect all steps of SCEV expressions.
+struct SCEVCollectStrides {
+ ScalarEvolution &SE;
+ SmallVectorImpl<const SCEV *> &Strides;
+
+ SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
+ : SE(SE), Strides(S) {}
+
+ bool follow(const SCEV *S) {
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
+ Strides.push_back(AR->getStepRecurrence(SE));
+ return true;
+ }
+ bool isDone() const { return false; }
+};
+
+// Collect all SCEVUnknown and SCEVMulExpr expressions.
+struct SCEVCollectTerms {
+ SmallVectorImpl<const SCEV *> &Terms;
+
+ SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
+ : Terms(T) {}
+
+ bool follow(const SCEV *S) {
+ if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S)) {
+ if (!containsUndefs(S))
+ Terms.push_back(S);
+
+ // Stop recursion: once we collected a term, do not walk its operands.
+ return false;
+ }
+
+ // Keep looking.
+ return true;
+ }
+ bool isDone() const { return false; }
+};
+}
+
+/// Find parametric terms in this SCEVAddRecExpr.
+void SCEVAddRecExpr::collectParametricTerms(
+ ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Terms) const {
+ SmallVector<const SCEV *, 4> Strides;
+ SCEVCollectStrides StrideCollector(SE, Strides);
+ visitAll(this, StrideCollector);
+
+ DEBUG({
+ dbgs() << "Strides:\n";
+ for (const SCEV *S : Strides)
+ dbgs() << *S << "\n";
+ });
+
+ for (const SCEV *S : Strides) {
+ SCEVCollectTerms TermCollector(Terms);
+ visitAll(S, TermCollector);
+ }
+
+ DEBUG({
+ dbgs() << "Terms:\n";
+ for (const SCEV *T : Terms)
+ dbgs() << *T << "\n";
+ });
+}
+
+static bool findArrayDimensionsRec(ScalarEvolution &SE,
+ SmallVectorImpl<const SCEV *> &Terms,
+ SmallVectorImpl<const SCEV *> &Sizes) {
+ int Last = Terms.size() - 1;
+ const SCEV *Step = Terms[Last];
+
+ // End of recursion.
+ if (Last == 0) {
+ if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
+ SmallVector<const SCEV *, 2> Qs;
+ for (const SCEV *Op : M->operands())
+ if (!isa<SCEVConstant>(Op))
+ Qs.push_back(Op);
+
+ Step = SE.getMulExpr(Qs);
+ }
+
+ Sizes.push_back(Step);
+ return true;
+ }
+
+ for (const SCEV *&Term : Terms) {
+ // Normalize the terms before the next call to findArrayDimensionsRec.
+ const SCEV *Q, *R;
+ SCEVSDivision::divide(SE, Term, Step, &Q, &R);
+
+ // Bail out when GCD does not evenly divide one of the terms.
+ if (!R->isZero())
+ return false;
+
+ Term = Q;
+ }
+
+ // Remove all SCEVConstants.
+ Terms.erase(std::remove_if(Terms.begin(), Terms.end(), [](const SCEV *E) {
+ return isa<SCEVConstant>(E);
+ }),
+ Terms.end());
+
+ if (Terms.size() > 0)
+ if (!findArrayDimensionsRec(SE, Terms, Sizes))
+ return false;
+
+ Sizes.push_back(Step);
+ return true;
+}
+
+namespace {
+struct FindParameter {
+ bool FoundParameter;
+ FindParameter() : FoundParameter(false) {}
+
+ bool follow(const SCEV *S) {
+ if (isa<SCEVUnknown>(S)) {
+ FoundParameter = true;
+ // Stop recursion: we found a parameter.
+ return false;
+ }
+ // Keep looking.
+ return true;
+ }
+ bool isDone() const {
+ // Stop recursion if we have found a parameter.
+ return FoundParameter;
+ }
+};
+}
+
+// Returns true when S contains at least a SCEVUnknown parameter.
+static inline bool
+containsParameters(const SCEV *S) {
+ FindParameter F;
+ SCEVTraversal<FindParameter> ST(F);
+ ST.visitAll(S);
+
+ return F.FoundParameter;
+}
+
+// Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
+static inline bool
+containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
+ for (const SCEV *T : Terms)
+ if (containsParameters(T))
+ return true;
+ return false;
+}
+
+// Return the number of product terms in S.
+static inline int numberOfTerms(const SCEV *S) {
+ if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
+ return Expr->getNumOperands();
+ return 1;
+}
+
+static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
+ if (isa<SCEVConstant>(T))
+ return nullptr;
+
+ if (isa<SCEVUnknown>(T))
+ return T;
+
+ if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
+ SmallVector<const SCEV *, 2> Factors;
+ for (const SCEV *Op : M->operands())
+ if (!isa<SCEVConstant>(Op))
+ Factors.push_back(Op);
+
+ return SE.getMulExpr(Factors);
+ }
+
+ return T;
+}
+
+/// Return the size of an element read or written by Inst.
+const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
+ Type *Ty;
+ if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
+ Ty = Store->getValueOperand()->getType();
+ else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
+ Ty = Load->getType();
+ else
+ return nullptr;
+
+ Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
+ return getSizeOfExpr(ETy, Ty);
+}
+
+/// Second step of delinearization: compute the array dimensions Sizes from the
+/// set of Terms extracted from the memory access function of this SCEVAddRec.
+void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
+ SmallVectorImpl<const SCEV *> &Sizes,
+ const SCEV *ElementSize) const {
+
+ if (Terms.size() < 1 || !ElementSize)
+ return;
+
+ // Early return when Terms do not contain parameters: we do not delinearize
+ // non parametric SCEVs.
+ if (!containsParameters(Terms))
+ return;
+
+ DEBUG({
+ dbgs() << "Terms:\n";
+ for (const SCEV *T : Terms)
+ dbgs() << *T << "\n";
+ });
+
+ // Remove duplicates.
+ std::sort(Terms.begin(), Terms.end());
+ Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
+
+ // Put larger terms first.
+ std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
+ return numberOfTerms(LHS) > numberOfTerms(RHS);
+ });
+
+ ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
+
+ // Divide all terms by the element size.
+ for (const SCEV *&Term : Terms) {
+ const SCEV *Q, *R;
+ SCEVSDivision::divide(SE, Term, ElementSize, &Q, &R);
+ Term = Q;
+ }
+
+ SmallVector<const SCEV *, 4> NewTerms;
+
+ // Remove constant factors.
+ for (const SCEV *T : Terms)
+ if (const SCEV *NewT = removeConstantFactors(SE, T))
+ NewTerms.push_back(NewT);
+
+ DEBUG({
+ dbgs() << "Terms after sorting:\n";
+ for (const SCEV *T : NewTerms)
+ dbgs() << *T << "\n";
+ });
+
+ if (NewTerms.empty() ||
+ !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
+ Sizes.clear();
+ return;
+ }
+
+ // The last element to be pushed into Sizes is the size of an element.
+ Sizes.push_back(ElementSize);
+
+ DEBUG({
+ dbgs() << "Sizes:\n";
+ for (const SCEV *S : Sizes)
+ dbgs() << *S << "\n";
+ });
+}
+
+/// Third step of delinearization: compute the access functions for the
+/// Subscripts based on the dimensions in Sizes.
+void SCEVAddRecExpr::computeAccessFunctions(
+ ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Subscripts,
+ SmallVectorImpl<const SCEV *> &Sizes) const {
+
+ // Early exit in case this SCEV is not an affine multivariate function.
+ if (Sizes.empty() || !this->isAffine())
+ return;
+
+ const SCEV *Res = this;
+ int Last = Sizes.size() - 1;
+ for (int i = Last; i >= 0; i--) {
+ const SCEV *Q, *R;
+ SCEVSDivision::divide(SE, Res, Sizes[i], &Q, &R);
+
+ DEBUG({
+ dbgs() << "Res: " << *Res << "\n";
+ dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
+ dbgs() << "Res divided by Sizes[i]:\n";
+ dbgs() << "Quotient: " << *Q << "\n";
+ dbgs() << "Remainder: " << *R << "\n";
+ });
+
+ Res = Q;
+
+ // Do not record the last subscript corresponding to the size of elements in
+ // the array.
+ if (i == Last) {
+
+ // Bail out if the remainder is too complex.
+ if (isa<SCEVAddRecExpr>(R)) {
+ Subscripts.clear();
+ Sizes.clear();
+ return;
+ }
+
+ continue;
+ }
+
+ // Record the access function for the current subscript.
+ Subscripts.push_back(R);
+ }
+
+ // Also push in last position the remainder of the last division: it will be
+ // the access function of the innermost dimension.
+ Subscripts.push_back(Res);
+
+ std::reverse(Subscripts.begin(), Subscripts.end());
+
+ DEBUG({
+ dbgs() << "Subscripts:\n";
+ for (const SCEV *S : Subscripts)
+ dbgs() << *S << "\n";
+ });
+}
+
+/// Splits the SCEV into two vectors of SCEVs representing the subscripts and
+/// sizes of an array access. Returns the remainder of the delinearization that
+/// is the offset start of the array. The SCEV->delinearize algorithm computes
+/// the multiples of SCEV coefficients: that is a pattern matching of sub
+/// expressions in the stride and base of a SCEV corresponding to the
+/// computation of a GCD (greatest common divisor) of base and stride. When
+/// SCEV->delinearize fails, it returns the SCEV unchanged.
+///
+/// For example: when analyzing the memory access A[i][j][k] in this loop nest
+///
+/// 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][j][k] = 1.0;
+/// }
+///
+/// the delinearization input is the following AddRec SCEV:
+///
+/// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
+///
+/// From this SCEV, we are able to say that the base offset of the access is %A
+/// because it appears as an offset that does not divide any of the strides in
+/// the loops:
+///
+/// CHECK: Base offset: %A
+///
+/// and then SCEV->delinearize determines the size of some of the dimensions of
+/// the array as these are the multiples by which the strides are happening:
+///
+/// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
+///
+/// Note that the outermost dimension remains of UnknownSize because there are
+/// no strides that would help identifying the size of the last dimension: when
+/// the array has been statically allocated, one could compute the size of that
+/// dimension by dividing the overall size of the array by the size of the known
+/// dimensions: %m * %o * 8.
+///
+/// Finally delinearize provides the access functions for the array reference
+/// that does correspond to A[i][j][k] of the above C testcase:
+///
+/// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
+///
+/// The testcases are checking the output of a function pass:
+/// DelinearizationPass that walks through all loads and stores of a function
+/// asking for the SCEV of the memory access with respect to all enclosing
+/// loops, calling SCEV->delinearize on that and printing the results.
+
+void SCEVAddRecExpr::delinearize(ScalarEvolution &SE,
+ SmallVectorImpl<const SCEV *> &Subscripts,
+ SmallVectorImpl<const SCEV *> &Sizes,
+ const SCEV *ElementSize) const {
+ // First step: collect parametric terms.
+ SmallVector<const SCEV *, 4> Terms;
+ collectParametricTerms(SE, Terms);
+
+ if (Terms.empty())
+ return;
+
+ // Second step: find subscript sizes.
+ SE.findArrayDimensions(Terms, Sizes, ElementSize);
+
+ if (Sizes.empty())
+ return;
+
+ // Third step: compute the access functions for each subscript.
+ computeAccessFunctions(SE, Subscripts, Sizes);
+ if (Subscripts.empty())
+ return;
+
+ DEBUG({
+ dbgs() << "succeeded to delinearize " << *this << "\n";
+ dbgs() << "ArrayDecl[UnknownSize]";
+ for (const SCEV *S : Sizes)
+ dbgs() << "[" << *S << "]";
+
+ dbgs() << "\nArrayRef";
+ for (const SCEV *S : Subscripts)
+ dbgs() << "[" << *S << "]";
+ dbgs() << "\n";
+ });
+}
//===----------------------------------------------------------------------===//
// SCEVCallbackVH Class Implementation
// so that future queries will recompute the expressions using the new
// value.
Value *Old = getValPtr();
- SmallVector<User *, 16> Worklist;
+ SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
SmallPtrSet<User *, 8> Visited;
- for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
- UI != UE; ++UI)
- Worklist.push_back(*UI);
while (!Worklist.empty()) {
User *U = Worklist.pop_back_val();
// Deleting the Old value will cause this to dangle. Postpone
// that until everything else is done.
if (U == Old)
continue;
- if (!Visited.insert(U))
+ if (!Visited.insert(U).second)
continue;
if (PHINode *PN = dyn_cast<PHINode>(U))
SE->ConstantEvolutionLoopExitValue.erase(PN);
SE->ValueExprMap.erase(U);
- for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
- UI != UE; ++UI)
- Worklist.push_back(*UI);
+ Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
}
// Delete the Old value.
if (PHINode *PN = dyn_cast<PHINode>(Old))
//===----------------------------------------------------------------------===//
ScalarEvolution::ScalarEvolution()
- : FunctionPass(ID), FirstUnknown(0) {
+ : FunctionPass(ID), ValuesAtScopes(64), LoopDispositions(64),
+ BlockDispositions(64), FirstUnknown(nullptr) {
initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
}
bool ScalarEvolution::runOnFunction(Function &F) {
this->F = &F;
+ AT = &getAnalysis<AssumptionTracker>();
LI = &getAnalysis<LoopInfo>();
- TD = getAnalysisIfAvailable<DataLayout>();
+ DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : nullptr;
TLI = &getAnalysis<TargetLibraryInfo>();
- DT = &getAnalysis<DominatorTree>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
return false;
}
// destructors, so that they release their references to their values.
for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
U->~SCEVUnknown();
- FirstUnknown = 0;
+ FirstUnknown = nullptr;
ValueExprMap.clear();
void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
+ AU.addRequired<AssumptionTracker>();
AU.addRequiredTransitive<LoopInfo>();
- AU.addRequiredTransitive<DominatorTree>();
+ AU.addRequiredTransitive<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfo>();
}
PrintLoopInfo(OS, SE, *I);
OS << "Loop ";
- WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
+ L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
OS << ": ";
SmallVector<BasicBlock *, 8> ExitBlocks;
OS << "\n"
"Loop ";
- WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
+ L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
OS << ": ";
if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
OS << "Classifying expressions for: ";
- WriteAsOperand(OS, F, /*PrintType=*/false);
+ F->printAsOperand(OS, /*PrintType=*/false);
OS << "\n";
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
}
OS << "Determining loop execution counts for: ";
- WriteAsOperand(OS, F, /*PrintType=*/false);
+ F->printAsOperand(OS, /*PrintType=*/false);
OS << "\n";
for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
PrintLoopInfo(OS, &SE, *I);
ScalarEvolution::LoopDisposition
ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
- std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
- std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
- Values.insert(std::make_pair(L, LoopVariant));
- if (!Pair.second)
- return Pair.first->second;
-
+ SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values = LoopDispositions[S];
+ for (unsigned u = 0; u < Values.size(); u++) {
+ if (Values[u].first == L)
+ return Values[u].second;
+ }
+ Values.push_back(std::make_pair(L, LoopVariant));
LoopDisposition D = computeLoopDisposition(S, L);
- return LoopDispositions[S][L] = D;
+ SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values2 = LoopDispositions[S];
+ for (unsigned u = Values2.size(); u > 0; u--) {
+ if (Values2[u - 1].first == L) {
+ Values2[u - 1].second = D;
+ break;
+ }
+ }
+ return D;
}
ScalarEvolution::LoopDisposition
ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
- switch (S->getSCEVType()) {
+ switch (static_cast<SCEVTypes>(S->getSCEVType())) {
case scConstant:
return LoopInvariant;
case scTruncate:
return LoopInvariant;
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
- default: llvm_unreachable("Unknown SCEV kind!");
}
+ llvm_unreachable("Unknown SCEV kind!");
}
bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
ScalarEvolution::BlockDisposition
ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
- std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
- std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
- Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
- if (!Pair.second)
- return Pair.first->second;
-
+ SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values = BlockDispositions[S];
+ for (unsigned u = 0; u < Values.size(); u++) {
+ if (Values[u].first == BB)
+ return Values[u].second;
+ }
+ Values.push_back(std::make_pair(BB, DoesNotDominateBlock));
BlockDisposition D = computeBlockDisposition(S, BB);
- return BlockDispositions[S][BB] = D;
+ SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values2 = BlockDispositions[S];
+ for (unsigned u = Values2.size(); u > 0; u--) {
+ if (Values2[u - 1].first == BB) {
+ Values2[u - 1].second = D;
+ break;
+ }
+ }
+ return D;
}
ScalarEvolution::BlockDisposition
ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
- switch (S->getSCEVType()) {
+ switch (static_cast<SCEVTypes>(S->getSCEVType())) {
case scConstant:
return ProperlyDominatesBlock;
case scTruncate:
return ProperlyDominatesBlock;
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
- default:
- llvm_unreachable("Unknown SCEV kind!");
}
+ llvm_unreachable("Unknown SCEV kind!");
}
bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
typedef DenseMap<const Loop *, std::string> VerifyMap;
-/// replaceSubString - Replaces all occurences of From in Str with To.
+/// replaceSubString - Replaces all occurrences of From in Str with To.
static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
size_t Pos = 0;
while ((Pos = Str.find(From, Pos)) != std::string::npos) {
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