#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
+#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/InstIterator.h"
-#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ManagedStatic.h"
#include "llvm/ADT/Statistic.h"
#include <cmath>
+#include <iostream>
#include <algorithm>
using namespace llvm;
namespace {
- RegisterAnalysis<ScalarEvolution>
+ RegisterPass<ScalarEvolution>
R("scalar-evolution", "Scalar Evolution Analysis");
Statistic<>
cl::opt<unsigned>
MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
- cl::desc("Maximum number of iterations SCEV will symbolically execute a constant derived loop"),
+ cl::desc("Maximum number of iterations SCEV will "
+ "symbolically execute a constant derived loop"),
cl::init(100));
}
// SCEVConstants - Only allow the creation of one SCEVConstant for any
// particular value. Don't use a SCEVHandle here, or else the object will
// never be deleted!
-static std::map<ConstantInt*, SCEVConstant*> SCEVConstants;
+static ManagedStatic<std::map<ConstantInt*, SCEVConstant*> > SCEVConstants;
SCEVConstant::~SCEVConstant() {
- SCEVConstants.erase(V);
+ SCEVConstants->erase(V);
}
SCEVHandle SCEVConstant::get(ConstantInt *V) {
// Make sure that SCEVConstant instances are all unsigned.
if (V->getType()->isSigned()) {
const Type *NewTy = V->getType()->getUnsignedVersion();
- V = cast<ConstantUInt>(ConstantExpr::getCast(V, NewTy));
+ V = cast<ConstantInt>(ConstantExpr::getCast(V, NewTy));
}
- SCEVConstant *&R = SCEVConstants[V];
+ SCEVConstant *&R = (*SCEVConstants)[V];
if (R == 0) R = new SCEVConstant(V);
return R;
}
// SCEVTruncates - Only allow the creation of one SCEVTruncateExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will
// never be deleted!
-static std::map<std::pair<SCEV*, const Type*>, SCEVTruncateExpr*> SCEVTruncates;
+static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
+ SCEVTruncateExpr*> > SCEVTruncates;
SCEVTruncateExpr::SCEVTruncateExpr(const SCEVHandle &op, const Type *ty)
: SCEV(scTruncate), Op(op), Ty(ty) {
}
SCEVTruncateExpr::~SCEVTruncateExpr() {
- SCEVTruncates.erase(std::make_pair(Op, Ty));
+ SCEVTruncates->erase(std::make_pair(Op, Ty));
}
ConstantRange SCEVTruncateExpr::getValueRange() const {
// SCEVZeroExtends - Only allow the creation of one SCEVZeroExtendExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
-static std::map<std::pair<SCEV*, const Type*>,
- SCEVZeroExtendExpr*> SCEVZeroExtends;
+static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
+ SCEVZeroExtendExpr*> > SCEVZeroExtends;
SCEVZeroExtendExpr::SCEVZeroExtendExpr(const SCEVHandle &op, const Type *ty)
: SCEV(scTruncate), Op(op), Ty(ty) {
}
SCEVZeroExtendExpr::~SCEVZeroExtendExpr() {
- SCEVZeroExtends.erase(std::make_pair(Op, Ty));
+ SCEVZeroExtends->erase(std::make_pair(Op, Ty));
}
ConstantRange SCEVZeroExtendExpr::getValueRange() const {
// SCEVCommExprs - Only allow the creation of one SCEVCommutativeExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
-static std::map<std::pair<unsigned, std::vector<SCEV*> >,
- SCEVCommutativeExpr*> SCEVCommExprs;
+static ManagedStatic<std::map<std::pair<unsigned, std::vector<SCEV*> >,
+ SCEVCommutativeExpr*> > SCEVCommExprs;
SCEVCommutativeExpr::~SCEVCommutativeExpr() {
- SCEVCommExprs.erase(std::make_pair(getSCEVType(),
- std::vector<SCEV*>(Operands.begin(),
- Operands.end())));
+ SCEVCommExprs->erase(std::make_pair(getSCEVType(),
+ std::vector<SCEV*>(Operands.begin(),
+ Operands.end())));
}
void SCEVCommutativeExpr::print(std::ostream &OS) const {
}
-// SCEVUDivs - Only allow the creation of one SCEVUDivExpr for any particular
+// SCEVSDivs - Only allow the creation of one SCEVSDivExpr for any particular
// input. Don't use a SCEVHandle here, or else the object will never be
// deleted!
-static std::map<std::pair<SCEV*, SCEV*>, SCEVUDivExpr*> SCEVUDivs;
+static ManagedStatic<std::map<std::pair<SCEV*, SCEV*>,
+ SCEVSDivExpr*> > SCEVSDivs;
-SCEVUDivExpr::~SCEVUDivExpr() {
- SCEVUDivs.erase(std::make_pair(LHS, RHS));
+SCEVSDivExpr::~SCEVSDivExpr() {
+ SCEVSDivs->erase(std::make_pair(LHS, RHS));
}
-void SCEVUDivExpr::print(std::ostream &OS) const {
- OS << "(" << *LHS << " /u " << *RHS << ")";
+void SCEVSDivExpr::print(std::ostream &OS) const {
+ OS << "(" << *LHS << " /s " << *RHS << ")";
}
-const Type *SCEVUDivExpr::getType() const {
+const Type *SCEVSDivExpr::getType() const {
const Type *Ty = LHS->getType();
- if (Ty->isSigned()) Ty = Ty->getUnsignedVersion();
+ if (Ty->isUnsigned()) Ty = Ty->getSignedVersion();
return Ty;
}
// SCEVAddRecExprs - Only allow the creation of one SCEVAddRecExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
-static std::map<std::pair<const Loop *, std::vector<SCEV*> >,
- SCEVAddRecExpr*> SCEVAddRecExprs;
+static ManagedStatic<std::map<std::pair<const Loop *, std::vector<SCEV*> >,
+ SCEVAddRecExpr*> > SCEVAddRecExprs;
SCEVAddRecExpr::~SCEVAddRecExpr() {
- SCEVAddRecExprs.erase(std::make_pair(L,
- std::vector<SCEV*>(Operands.begin(),
- Operands.end())));
+ SCEVAddRecExprs->erase(std::make_pair(L,
+ std::vector<SCEV*>(Operands.begin(),
+ Operands.end())));
}
SCEVHandle SCEVAddRecExpr::
bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
// This recurrence is invariant w.r.t to QueryLoop iff QueryLoop doesn't
- // contain L.
- return !QueryLoop->contains(L->getHeader());
+ // contain L and if the start is invariant.
+ return !QueryLoop->contains(L->getHeader()) &&
+ getOperand(0)->isLoopInvariant(QueryLoop);
}
// SCEVUnknowns - Only allow the creation of one SCEVUnknown for any particular
// value. Don't use a SCEVHandle here, or else the object will never be
// deleted!
-static std::map<Value*, SCEVUnknown*> SCEVUnknowns;
+static ManagedStatic<std::map<Value*, SCEVUnknown*> > SCEVUnknowns;
-SCEVUnknown::~SCEVUnknown() { SCEVUnknowns.erase(V); }
+SCEVUnknown::~SCEVUnknown() { SCEVUnknowns->erase(V); }
bool SCEVUnknown::isLoopInvariant(const Loop *L) const {
// All non-instruction values are loop invariant. All instructions are loop
/// SCEVComplexityCompare - Return true if the complexity of the LHS is less
/// than the complexity of the RHS. This comparator is used to canonicalize
/// expressions.
- struct SCEVComplexityCompare {
+ struct VISIBILITY_HIDDEN SCEVComplexityCompare {
bool operator()(SCEV *LHS, SCEV *RHS) {
return LHS->getSCEVType() < RHS->getSCEVType();
}
else if (Ty->isFloatingPoint())
C = ConstantFP::get(Ty, Val);
else if (Ty->isSigned())
- C = ConstantSInt::get(Ty, Val);
+ C = ConstantInt::get(Ty, Val);
else {
- C = ConstantSInt::get(Ty->getSignedVersion(), Val);
+ C = ConstantInt::get(Ty->getSignedVersion(), Val);
C = ConstantExpr::getCast(C, Ty);
}
return SCEVUnknown::get(C);
// Handle this case efficiently, it is common to have constant iteration
// counts while computing loop exit values.
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
- uint64_t Val = SC->getValue()->getRawValue();
+ uint64_t Val = SC->getValue()->getZExtValue();
uint64_t Result = 1;
for (; NumSteps; --NumSteps)
Result *= Val-(NumSteps-1);
- Constant *Res = ConstantUInt::get(Type::ULongTy, Result);
+ Constant *Res = ConstantInt::get(Type::ULongTy, Result);
return SCEVUnknown::get(ConstantExpr::getCast(Res, V->getType()));
}
for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
SCEVHandle BC = PartialFact(It, i);
Divisor *= i;
- SCEVHandle Val = SCEVUDivExpr::get(SCEVMulExpr::get(BC, getOperand(i)),
+ SCEVHandle Val = SCEVSDivExpr::get(SCEVMulExpr::get(BC, getOperand(i)),
SCEVUnknown::getIntegerSCEV(Divisor,Ty));
Result = SCEVAddExpr::get(Result, Val);
}
return SCEVAddRecExpr::get(Operands, AddRec->getLoop());
}
- SCEVTruncateExpr *&Result = SCEVTruncates[std::make_pair(Op, Ty)];
+ SCEVTruncateExpr *&Result = (*SCEVTruncates)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVTruncateExpr(Op, Ty);
return Result;
}
// operands (often constants). This would allow analysis of something like
// this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
- SCEVZeroExtendExpr *&Result = SCEVZeroExtends[std::make_pair(Op, Ty)];
+ SCEVZeroExtendExpr *&Result = (*SCEVZeroExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVZeroExtendExpr(Op, Ty);
return Result;
}
// Okay, it looks like we really DO need an add expr. Check to see if we
// already have one, otherwise create a new one.
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
- SCEVCommutativeExpr *&Result = SCEVCommExprs[std::make_pair(scAddExpr,
- SCEVOps)];
+ SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scAddExpr,
+ SCEVOps)];
if (Result == 0) Result = new SCEVAddExpr(Ops);
return Result;
}
// Okay, it looks like we really DO need an mul expr. Check to see if we
// already have one, otherwise create a new one.
std::vector<SCEV*> SCEVOps(Ops.begin(), Ops.end());
- SCEVCommutativeExpr *&Result = SCEVCommExprs[std::make_pair(scMulExpr,
- SCEVOps)];
+ SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scMulExpr,
+ SCEVOps)];
if (Result == 0)
Result = new SCEVMulExpr(Ops);
return Result;
}
-SCEVHandle SCEVUDivExpr::get(const SCEVHandle &LHS, const SCEVHandle &RHS) {
+SCEVHandle SCEVSDivExpr::get(const SCEVHandle &LHS, const SCEVHandle &RHS) {
if (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
if (RHSC->getValue()->equalsInt(1))
- return LHS; // X /u 1 --> x
+ return LHS; // X /s 1 --> x
if (RHSC->getValue()->isAllOnesValue())
- return SCEV::getNegativeSCEV(LHS); // X /u -1 --> -x
+ return SCEV::getNegativeSCEV(LHS); // X /s -1 --> -x
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
Constant *LHSCV = LHSC->getValue();
Constant *RHSCV = RHSC->getValue();
- if (LHSCV->getType()->isSigned())
+ if (LHSCV->getType()->isUnsigned())
LHSCV = ConstantExpr::getCast(LHSCV,
- LHSCV->getType()->getUnsignedVersion());
- if (RHSCV->getType()->isSigned())
+ LHSCV->getType()->getSignedVersion());
+ if (RHSCV->getType()->isUnsigned())
RHSCV = ConstantExpr::getCast(RHSCV, LHSCV->getType());
return SCEVUnknown::get(ConstantExpr::getDiv(LHSCV, RHSCV));
}
// FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
- SCEVUDivExpr *&Result = SCEVUDivs[std::make_pair(LHS, RHS)];
- if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
+ SCEVSDivExpr *&Result = (*SCEVSDivs)[std::make_pair(LHS, RHS)];
+ if (Result == 0) Result = new SCEVSDivExpr(LHS, RHS);
return Result;
}
}
SCEVAddRecExpr *&Result =
- SCEVAddRecExprs[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
- Operands.end()))];
+ (*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
+ Operands.end()))];
if (Result == 0) Result = new SCEVAddRecExpr(Operands, L);
return Result;
}
SCEVHandle SCEVUnknown::get(Value *V) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
return SCEVConstant::get(CI);
- SCEVUnknown *&Result = SCEVUnknowns[V];
+ SCEVUnknown *&Result = (*SCEVUnknowns)[V];
if (Result == 0) Result = new SCEVUnknown(V);
return Result;
}
/// evolution code.
///
namespace {
- struct ScalarEvolutionsImpl {
+ struct VISIBILITY_HIDDEN ScalarEvolutionsImpl {
/// F - The function we are analyzing.
///
Function &F;
/// HowFarToZero - Return the number of times a backedge comparing the
/// specified value to zero will execute. If not computable, return
- /// UnknownValue
+ /// UnknownValue.
SCEVHandle HowFarToZero(SCEV *V, const Loop *L);
/// HowFarToNonZero - Return the number of times a backedge checking the
/// specified value for nonzero will execute. If not computable, return
- /// UnknownValue
+ /// UnknownValue.
SCEVHandle HowFarToNonZero(SCEV *V, const Loop *L);
+ /// HowManyLessThans - Return the number of times a backedge containing the
+ /// specified less-than comparison will execute. If not computable, return
+ /// UnknownValue.
+ SCEVHandle HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L);
+
/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
/// in the header of its containing loop, we know the loop executes a
/// constant number of times, and the PHI node is just a recurrence
SCEVHandle StartVal = getSCEV(PN->getIncomingValue(IncomingEdge));
SCEVHandle PHISCEV = SCEVAddRecExpr::get(StartVal, Accum, L);
+ // Okay, for the entire analysis of this edge we assumed the PHI
+ // to be symbolic. We now need to go back and update all of the
+ // entries for the scalars that use the PHI (except for the PHI
+ // itself) to use the new analyzed value instead of the "symbolic"
+ // value.
+ ReplaceSymbolicValueWithConcrete(PN, SymbolicName, PHISCEV);
+ return PHISCEV;
+ }
+ }
+ } else if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(BEValue)) {
+ // Otherwise, this could be a loop like this:
+ // i = 0; for (j = 1; ..; ++j) { .... i = j; }
+ // In this case, j = {1,+,1} and BEValue is j.
+ // Because the other in-value of i (0) fits the evolution of BEValue
+ // i really is an addrec evolution.
+ if (AddRec->getLoop() == L && AddRec->isAffine()) {
+ SCEVHandle StartVal = getSCEV(PN->getIncomingValue(IncomingEdge));
+
+ // If StartVal = j.start - j.stride, we can use StartVal as the
+ // initial step of the addrec evolution.
+ if (StartVal == SCEV::getMinusSCEV(AddRec->getOperand(0),
+ AddRec->getOperand(1))) {
+ SCEVHandle PHISCEV =
+ SCEVAddRecExpr::get(StartVal, AddRec->getOperand(1), L);
+
// Okay, for the entire analysis of this edge we assumed the PHI
// to be symbolic. We now need to go back and update all of the
// entries for the scalars that use the PHI (except for the PHI
return SCEVMulExpr::get(getSCEV(I->getOperand(0)),
getSCEV(I->getOperand(1)));
case Instruction::Div:
- if (V->getType()->isInteger() && V->getType()->isUnsigned())
- return SCEVUDivExpr::get(getSCEV(I->getOperand(0)),
+ if (V->getType()->isInteger() && V->getType()->isSigned())
+ return SCEVSDivExpr::get(getSCEV(I->getOperand(0)),
getSCEV(I->getOperand(1)));
break;
}
break;
- case Instruction::Shr:
- if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
- if (V->getType()->isUnsigned()) {
- Constant *X = ConstantInt::get(V->getType(), 1);
- X = ConstantExpr::getShl(X, SA);
- return SCEVUDivExpr::get(getSCEV(I->getOperand(0)), getSCEV(X));
- }
- break;
-
case Instruction::Cast:
return createNodeForCast(cast<CastInst>(I));
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
}
break;
+ case Instruction::SetLT:
+ if (LHS->getType()->isInteger() &&
+ ExitCond->getOperand(0)->getType()->isSigned()) {
+ SCEVHandle TC = HowManyLessThans(LHS, RHS, L);
+ if (!isa<SCEVCouldNotCompute>(TC)) return TC;
+ }
+ break;
+ case Instruction::SetGT:
+ if (LHS->getType()->isInteger() &&
+ ExitCond->getOperand(0)->getType()->isSigned()) {
+ SCEVHandle TC = HowManyLessThans(RHS, LHS, L);
+ if (!isa<SCEVCouldNotCompute>(TC)) return TC;
+ }
+ break;
default:
#if 0
std::cerr << "ComputeIterationCount ";
const std::vector<ConstantInt*> &Indices) {
Constant *Init = GV->getInitializer();
for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
- uint64_t Idx = Indices[i]->getRawValue();
+ uint64_t Idx = Indices[i]->getZExtValue();
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
assert(Idx < CS->getNumOperands() && "Bad struct index!");
Init = cast<Constant>(CS->getOperand(Idx));
unsigned MaxSteps = MaxBruteForceIterations;
for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
- ConstantUInt *ItCst =
- ConstantUInt::get(IdxExpr->getType()->getUnsignedVersion(), IterationNum);
+ ConstantInt *ItCst =
+ ConstantInt::get(IdxExpr->getType()->getUnsignedVersion(), IterationNum);
ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst);
// Form the GEP offset.
// Evaluate the condition for this iteration.
Result = ConstantExpr::get(SetCCOpcode, Result, RHS);
if (!isa<ConstantBool>(Result)) break; // Couldn't decide for sure
- if (Result == ConstantBool::False) {
+ if (cast<ConstantBool>(Result)->getValue() == false) {
#if 0
std::cerr << "\n***\n*** Computed loop count " << *ItCst
<< "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
if (CondVal->getValue() == ExitWhen) {
ConstantEvolutionLoopExitValue[PN] = PHIVal;
++NumBruteForceTripCountsComputed;
- return SCEVConstant::get(ConstantUInt::get(Type::UIntTy, IterationNum));
+ return SCEVConstant::get(ConstantInt::get(Type::UIntTy, IterationNum));
}
// Compute the value of the PHI node for the next iteration.
// this is a constant evolving PHI node, get the final value at
// the specified iteration number.
Constant *RV = getConstantEvolutionLoopExitValue(PN,
- ICC->getValue()->getRawValue(),
+ ICC->getValue()->getZExtValue(),
LI);
if (RV) return SCEVUnknown::get(RV);
}
return Comm;
}
- if (SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(V)) {
- SCEVHandle LHS = getSCEVAtScope(UDiv->getLHS(), L);
+ if (SCEVSDivExpr *Div = dyn_cast<SCEVSDivExpr>(V)) {
+ SCEVHandle LHS = getSCEVAtScope(Div->getLHS(), L);
if (LHS == UnknownValue) return LHS;
- SCEVHandle RHS = getSCEVAtScope(UDiv->getRHS(), L);
+ SCEVHandle RHS = getSCEVAtScope(Div->getRHS(), L);
if (RHS == UnknownValue) return RHS;
- if (LHS == UDiv->getLHS() && RHS == UDiv->getRHS())
- return UDiv; // must be loop invariant
- return SCEVUDivExpr::get(LHS, RHS);
+ if (LHS == Div->getLHS() && RHS == Div->getRHS())
+ return Div; // must be loop invariant
+ return SCEVSDivExpr::get(LHS, RHS);
}
// If this is a loop recurrence for a loop that does not contain L, then we
SqrtTerm = ConstantExpr::getSub(ConstantExpr::getMul(B, B), SqrtTerm);
// Compute floor(sqrt(B^2-4ac))
- ConstantUInt *SqrtVal =
- cast<ConstantUInt>(ConstantExpr::getCast(SqrtTerm,
+ ConstantInt *SqrtVal =
+ cast<ConstantInt>(ConstantExpr::getCast(SqrtTerm,
SqrtTerm->getType()->getUnsignedVersion()));
- uint64_t SqrtValV = SqrtVal->getValue();
+ uint64_t SqrtValV = SqrtVal->getZExtValue();
uint64_t SqrtValV2 = (uint64_t)sqrt((double)SqrtValV);
// The square root might not be precise for arbitrary 64-bit integer
// values. Do some sanity checks to ensure it's correct.
return std::make_pair(CNC, CNC);
}
- SqrtVal = ConstantUInt::get(Type::ULongTy, SqrtValV2);
+ SqrtVal = ConstantInt::get(Type::ULongTy, SqrtValV2);
SqrtTerm = ConstantExpr::getCast(SqrtVal, SqrtTerm->getType());
Constant *NegB = ConstantExpr::getNeg(B);
if (ConstantBool *CB =
dyn_cast<ConstantBool>(ConstantExpr::getSetLT(R1->getValue(),
R2->getValue()))) {
- if (CB != ConstantBool::True)
+ if (CB->getValue() == false)
std::swap(R1, R2); // R1 is the minimum root now.
// We can only use this value if the chrec ends up with an exact zero
if (SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
Constant *Zero = Constant::getNullValue(C->getValue()->getType());
Constant *NonZero = ConstantExpr::getSetNE(C->getValue(), Zero);
- if (NonZero == ConstantBool::True)
+ if (NonZero == ConstantBool::getTrue())
return getSCEV(Zero);
return UnknownValue; // Otherwise it will loop infinitely.
}
return UnknownValue;
}
+/// HowManyLessThans - Return the number of times a backedge containing the
+/// specified less-than comparison will execute. If not computable, return
+/// UnknownValue.
+SCEVHandle ScalarEvolutionsImpl::
+HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L) {
+ // Only handle: "ADDREC < LoopInvariant".
+ if (!RHS->isLoopInvariant(L)) return UnknownValue;
+
+ SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
+ if (!AddRec || AddRec->getLoop() != L)
+ return UnknownValue;
+
+ if (AddRec->isAffine()) {
+ // FORNOW: We only support unit strides.
+ SCEVHandle One = SCEVUnknown::getIntegerSCEV(1, RHS->getType());
+ if (AddRec->getOperand(1) != One)
+ return UnknownValue;
+
+ // The number of iterations for "[n,+,1] < m", is m-n. However, we don't
+ // know that m is >= n on input to the loop. If it is, the condition return
+ // true zero times. What we really should return, for full generality, is
+ // SMAX(0, m-n). Since we cannot check this, we will instead check for a
+ // canonical loop form: most do-loops will have a check that dominates the
+ // loop, that only enters the loop if [n-1]<m. If we can find this check,
+ // we know that the SMAX will evaluate to m-n, because we know that m >= n.
+
+ // Search for the check.
+ BasicBlock *Preheader = L->getLoopPreheader();
+ BasicBlock *PreheaderDest = L->getHeader();
+ if (Preheader == 0) return UnknownValue;
+
+ BranchInst *LoopEntryPredicate =
+ dyn_cast<BranchInst>(Preheader->getTerminator());
+ if (!LoopEntryPredicate) return UnknownValue;
+
+ // This might be a critical edge broken out. If the loop preheader ends in
+ // an unconditional branch to the loop, check to see if the preheader has a
+ // single predecessor, and if so, look for its terminator.
+ while (LoopEntryPredicate->isUnconditional()) {
+ PreheaderDest = Preheader;
+ Preheader = Preheader->getSinglePredecessor();
+ if (!Preheader) return UnknownValue; // Multiple preds.
+
+ LoopEntryPredicate =
+ dyn_cast<BranchInst>(Preheader->getTerminator());
+ if (!LoopEntryPredicate) return UnknownValue;
+ }
+
+ // Now that we found a conditional branch that dominates the loop, check to
+ // see if it is the comparison we are looking for.
+ SetCondInst *SCI =dyn_cast<SetCondInst>(LoopEntryPredicate->getCondition());
+ if (!SCI) return UnknownValue;
+ Value *PreCondLHS = SCI->getOperand(0);
+ Value *PreCondRHS = SCI->getOperand(1);
+ Instruction::BinaryOps Cond;
+ if (LoopEntryPredicate->getSuccessor(0) == PreheaderDest)
+ Cond = SCI->getOpcode();
+ else
+ Cond = SCI->getInverseCondition();
+
+ switch (Cond) {
+ case Instruction::SetGT:
+ std::swap(PreCondLHS, PreCondRHS);
+ Cond = Instruction::SetLT;
+ // Fall Through.
+ case Instruction::SetLT:
+ if (PreCondLHS->getType()->isInteger() &&
+ PreCondLHS->getType()->isSigned()) {
+ if (RHS != getSCEV(PreCondRHS))
+ return UnknownValue; // Not a comparison against 'm'.
+
+ if (SCEV::getMinusSCEV(AddRec->getOperand(0), One)
+ != getSCEV(PreCondLHS))
+ return UnknownValue; // Not a comparison against 'n-1'.
+ break;
+ } else {
+ return UnknownValue;
+ }
+ default: break;
+ }
+
+ //std::cerr << "Computed Loop Trip Count as: " <<
+ // *SCEV::getMinusSCEV(RHS, AddRec->getOperand(0)) << "\n";
+ return SCEV::getMinusSCEV(RHS, AddRec->getOperand(0));
+ }
+
+ return UnknownValue;
+}
+
/// getNumIterationsInRange - Return the number of iterations of this loop that
/// produce values in the specified constant range. Another way of looking at
/// this is that it returns the first iteration number where the value is not in
if (ConstantBool *CB =
dyn_cast<ConstantBool>(ConstantExpr::getSetLT(R1->getValue(),
R2->getValue()))) {
- if (CB != ConstantBool::True)
+ if (CB->getValue() == false)
std::swap(R1, R2); // R1 is the minimum root now.
// Make sure the root is not off by one. The returned iteration should
projects / oota-llvm.git / blobdiff