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Reapply 75252, with a fix to avoid the infinite recursion case. The

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check for avoiding re-analyzing a widening cast needed to happen
earlier, as getSCEV itself may result in a isLoopGuardedByCond query.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75511 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-07-13 21:35:55 +00:00
parent d97ea308ed
commit 85b05a2e60
3 changed files with 577 additions and 121 deletions
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62
include/llvm/Analysis/ScalarEvolution.h
View File

@ -26,6 +26,7 @@
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/DenseMap.h"
#include <iosfwd>
@ -330,12 +331,20 @@ namespace llvm {
/// found.
BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
/// isNecessaryCond - Test whether the given CondValue value is a condition
/// which is at least as strict as the one described by Pred, LHS, and RHS.
/// isNecessaryCond - Test whether the condition described by Pred, LHS,
/// and RHS is a necessary condition for the given Cond value to evaluate
/// to true.
bool isNecessaryCond(Value *Cond, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
bool Inverse);
/// isNecessaryCondOperands - Test whether the condition described by Pred,
/// LHS, and RHS is a necessary condition for the condition described by
/// Pred, FoundLHS, and FoundRHS to evaluate to true.
bool isNecessaryCondOperands(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
const SCEV *FoundLHS, const SCEV *FoundRHS);
/// 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
@ -495,10 +504,16 @@ namespace llvm {
/// isLoopGuardedByCond - Test whether entry to the loop is protected by
/// a conditional between LHS and RHS. This is used to help avoid max
/// expressions in loop trip counts.
/// expressions in loop trip counts, and to eliminate casts.
bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
/// protected by a conditional between LHS and RHS. This is used to
/// to eliminate casts.
bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// getBackedgeTakenCount - If the specified loop has a predictable
/// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
/// object. The backedge-taken count is the number of times the loop header
@ -534,13 +549,42 @@ namespace llvm {
/// bitwidth of S.
uint32_t GetMinTrailingZeros(const SCEV *S);
/// GetMinLeadingZeros - Determine the minimum number of zero bits that S is
/// guaranteed to begin with (at every loop iteration).
uint32_t GetMinLeadingZeros(const SCEV *S);
/// getUnsignedRange - Determine the unsigned range for a particular SCEV.
///
ConstantRange getUnsignedRange(const SCEV *S);
/// GetMinSignBits - Determine the minimum number of sign bits that S is
/// guaranteed to begin with.
uint32_t GetMinSignBits(const SCEV *S);
/// getSignedRange - Determine the signed range for a particular SCEV.
///
ConstantRange getSignedRange(const SCEV *S);
/// isKnownNegative - Test if the given expression is known to be negative.
///
bool isKnownNegative(const SCEV *S);
/// isKnownPositive - Test if the given expression is known to be positive.
///
bool isKnownPositive(const SCEV *S);
/// isKnownNonNegative - Test if the given expression is known to be
/// non-negative.
///
bool isKnownNonNegative(const SCEV *S);
/// isKnownNonPositive - Test if the given expression is known to be
/// non-positive.
///
bool isKnownNonPositive(const SCEV *S);
/// isKnownNonZero - Test if the given expression is known to be
/// non-zero.
///
bool isKnownNonZero(const SCEV *S);
/// isKnownNonZero - Test if the given expression is known to satisfy
/// the condition described by Pred, LHS, and RHS.
///
bool isKnownPredicate(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();

635
lib/Analysis/ScalarEvolution.cpp
View File

@ -787,6 +787,11 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
// this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
if (AR->isAffine()) {
const SCEV *Start = AR->getStart();
const SCEV *Step = AR->getStepRecurrence(*this);
unsigned BitWidth = getTypeSizeInBits(AR->getType());
const Loop *L = AR->getLoop();
// Check whether the backedge-taken count is SCEVCouldNotCompute.
// Note that this serves two purposes: It filters out loops that are
// simply not analyzable, and it covers the case where this code is
@ -795,12 +800,10 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
// in infinite recursion. In the later case, the analysis code will
// cope with a conservative value, and it will take care to purge
// that value once it has finished.
const SCEV *MaxBECount = getMaxBackedgeTakenCount(AR->getLoop());
const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
// Manually compute the final value for AR, checking for
// overflow.
const SCEV *Start = AR->getStart();
const SCEV *Step = AR->getStepRecurrence(*this);
// Check whether the backedge-taken count can be losslessly casted to
// the addrec's type. The count is always unsigned.
@ -809,8 +812,7 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
const SCEV *RecastedMaxBECount =
getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
if (MaxBECount == RecastedMaxBECount) {
const Type *WideTy =
IntegerType::get(getTypeSizeInBits(Start->getType()) * 2);
const Type *WideTy = IntegerType::get(BitWidth * 2);
// Check whether Start+Step*MaxBECount has no unsigned overflow.
const SCEV *ZMul =
getMulExpr(CastedMaxBECount,
@ -824,7 +826,7 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getZeroExtendExpr(Step, Ty),
AR->getLoop());
L);
// Similar to above, only this time treat the step value as signed.
// This covers loops that count down.
@ -840,7 +842,35 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
L);
}
// If the backedge is guarded by a comparison with the pre-inc value
// the addrec is safe. Also, if the entry is guarded by a comparison
// with the start value and the backedge is guarded by a comparison
// with the post-inc value, the addrec is safe.
if (isKnownPositive(Step)) {
const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
getUnsignedRange(Step).getUnsignedMax());
if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
(isLoopGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
AR->getPostIncExpr(*this), N)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getZeroExtendExpr(Step, Ty),
L);
} else if (isKnownNegative(Step)) {
const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
getSignedRange(Step).getSignedMin());
if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) &&
(isLoopGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) ||
isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
AR->getPostIncExpr(*this), N)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
L);
}
}
}
@ -889,6 +919,11 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
// this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
if (AR->isAffine()) {
const SCEV *Start = AR->getStart();
const SCEV *Step = AR->getStepRecurrence(*this);
unsigned BitWidth = getTypeSizeInBits(AR->getType());
const Loop *L = AR->getLoop();
// Check whether the backedge-taken count is SCEVCouldNotCompute.
// Note that this serves two purposes: It filters out loops that are
// simply not analyzable, and it covers the case where this code is
@ -897,12 +932,10 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
// in infinite recursion. In the later case, the analysis code will
// cope with a conservative value, and it will take care to purge
// that value once it has finished.
const SCEV *MaxBECount = getMaxBackedgeTakenCount(AR->getLoop());
const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
// Manually compute the final value for AR, checking for
// overflow.
const SCEV *Start = AR->getStart();
const SCEV *Step = AR->getStepRecurrence(*this);
// Check whether the backedge-taken count can be losslessly casted to
// the addrec's type. The count is always unsigned.
@ -911,8 +944,7 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
const SCEV *RecastedMaxBECount =
getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
if (MaxBECount == RecastedMaxBECount) {
const Type *WideTy =
IntegerType::get(getTypeSizeInBits(Start->getType()) * 2);
const Type *WideTy = IntegerType::get(BitWidth * 2);
// Check whether Start+Step*MaxBECount has no signed overflow.
const SCEV *SMul =
getMulExpr(CastedMaxBECount,
@ -926,7 +958,35 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
L);
}
// If the backedge is guarded by a comparison with the pre-inc value
// the addrec is safe. Also, if the entry is guarded by a comparison
// with the start value and the backedge is guarded by a comparison
// with the post-inc value, the addrec is safe.
if (isKnownPositive(Step)) {
const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
getSignedRange(Step).getSignedMax());
if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
(isLoopGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
AR->getPostIncExpr(*this), N)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
L);
} else if (isKnownNegative(Step)) {
const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
getSignedRange(Step).getSignedMin());
if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
(isLoopGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
AR->getPostIncExpr(*this), N)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
L);
}
}
}
@ -2368,19 +2428,16 @@ const SCEV *ScalarEvolution::createNodeForGEP(User *GEP) {
const StructLayout &SL = *TD->getStructLayout(STy);
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
uint64_t Offset = SL.getElementOffset(FieldNo);
TotalOffset = getAddExpr(TotalOffset,
getIntegerSCEV(Offset, IntPtrTy));
TotalOffset = getAddExpr(TotalOffset, getIntegerSCEV(Offset, IntPtrTy));
} else {
// For an array, add the element offset, explicitly scaled.
const SCEV *LocalOffset = getSCEV(Index);
if (!isa<PointerType>(LocalOffset->getType()))
// Getelementptr indicies are signed.
LocalOffset = getTruncateOrSignExtend(LocalOffset,
IntPtrTy);
LocalOffset = getTruncateOrSignExtend(LocalOffset, IntPtrTy);
LocalOffset =
getMulExpr(LocalOffset,
getIntegerSCEV(TD->getTypeAllocSize(*GTI),
IntPtrTy));
getIntegerSCEV(TD->getTypeAllocSize(*GTI), IntPtrTy));
TotalOffset = getAddExpr(TotalOffset, LocalOffset);
}
}
@ -2468,18 +2525,95 @@ ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
return 0;
}
uint32_t
ScalarEvolution::GetMinLeadingZeros(const SCEV *S) {
// TODO: Handle other SCEV expression types here.
/// getUnsignedRange - Determine the unsigned range for a particular SCEV.
///
ConstantRange
ScalarEvolution::getUnsignedRange(const SCEV *S) {
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
return C->getValue()->getValue().countLeadingZeros();
return ConstantRange(C->getValue()->getValue());
if (const SCEVZeroExtendExpr *C = dyn_cast<SCEVZeroExtendExpr>(S)) {
// A zero-extension cast adds zero bits.
return GetMinLeadingZeros(C->getOperand()) +
(getTypeSizeInBits(C->getType()) -
getTypeSizeInBits(C->getOperand()->getType()));
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
ConstantRange X = getUnsignedRange(Add->getOperand(0));
for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
X = X.add(getUnsignedRange(Add->getOperand(i)));
return X;
}
if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
ConstantRange X = getUnsignedRange(Mul->getOperand(0));
for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
return X;
}
if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
ConstantRange X = getUnsignedRange(SMax->getOperand(0));
for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
X = X.smax(getUnsignedRange(SMax->getOperand(i)));
return X;
}
if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
ConstantRange X = getUnsignedRange(UMax->getOperand(0));
for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
X = X.umax(getUnsignedRange(UMax->getOperand(i)));
return X;
}
if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
ConstantRange X = getUnsignedRange(UDiv->getLHS());
ConstantRange Y = getUnsignedRange(UDiv->getRHS());
return X.udiv(Y);
}
if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
ConstantRange X = getUnsignedRange(ZExt->getOperand());
return X.zeroExtend(cast<IntegerType>(ZExt->getType())->getBitWidth());
}
if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
ConstantRange X = getUnsignedRange(SExt->getOperand());
return X.signExtend(cast<IntegerType>(SExt->getType())->getBitWidth());
}
if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
ConstantRange X = getUnsignedRange(Trunc->getOperand());
return X.truncate(cast<IntegerType>(Trunc->getType())->getBitWidth());
}
ConstantRange FullSet(getTypeSizeInBits(S->getType()), true);
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
const SCEV *T = getBackedgeTakenCount(AddRec->getLoop());
const SCEVConstant *Trip = dyn_cast<SCEVConstant>(T);
if (!Trip) return FullSet;
// TODO: non-affine addrec
if (AddRec->isAffine()) {
const Type *Ty = AddRec->getType();
const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
if (getTypeSizeInBits(MaxBECount->getType()) <= getTypeSizeInBits(Ty)) {
MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
const SCEV *Start = AddRec->getStart();
const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this);
// Check for overflow.
if (!isKnownPredicate(ICmpInst::ICMP_ULE, Start, End))
return FullSet;
ConstantRange StartRange = getUnsignedRange(Start);
ConstantRange EndRange = getUnsignedRange(End);
APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
EndRange.getUnsignedMin());
APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
EndRange.getUnsignedMax());
if (Min.isMinValue() && Max.isMaxValue())
return ConstantRange(Min.getBitWidth(), /*isFullSet=*/true);
return ConstantRange(Min, Max+1);
}
}
}
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
@ -2488,67 +2622,119 @@ ScalarEvolution::GetMinLeadingZeros(const SCEV *S) {
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
return Zeros.countLeadingOnes();
return ConstantRange(Ones, ~Zeros);
}
return 1;
return FullSet;
}
uint32_t
ScalarEvolution::GetMinSignBits(const SCEV *S) {
// TODO: Handle other SCEV expression types here.
/// getSignedRange - Determine the signed range for a particular SCEV.
///
ConstantRange
ScalarEvolution::getSignedRange(const SCEV *S) {
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
const APInt &A = C->getValue()->getValue();
return A.isNegative() ? A.countLeadingOnes() :
A.countLeadingZeros();
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
return ConstantRange(C->getValue()->getValue());
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
ConstantRange X = getSignedRange(Add->getOperand(0));
for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
X = X.add(getSignedRange(Add->getOperand(i)));
return X;
}
if (const SCEVSignExtendExpr *C = dyn_cast<SCEVSignExtendExpr>(S)) {
// A sign-extension cast adds sign bits.
return GetMinSignBits(C->getOperand()) +
(getTypeSizeInBits(C->getType()) -
getTypeSizeInBits(C->getOperand()->getType()));
if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
ConstantRange X = getSignedRange(Mul->getOperand(0));
for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
X = X.multiply(getSignedRange(Mul->getOperand(i)));
return X;
}
if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
unsigned BitWidth = getTypeSizeInBits(A->getType());
if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
ConstantRange X = getSignedRange(SMax->getOperand(0));
for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
X = X.smax(getSignedRange(SMax->getOperand(i)));
return X;
}
// Special case decrementing a value (ADD X, -1):
if (const SCEVConstant *CRHS = dyn_cast<SCEVConstant>(A->getOperand(0)))
if (CRHS->isAllOnesValue()) {
SmallVector<const SCEV *, 4> OtherOps(A->op_begin() + 1, A->op_end());
const SCEV *OtherOpsAdd = getAddExpr(OtherOps);
unsigned LZ = GetMinLeadingZeros(OtherOpsAdd);
if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
ConstantRange X = getSignedRange(UMax->getOperand(0));
for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
X = X.umax(getSignedRange(UMax->getOperand(i)));
return X;
}
// If the input is known to be 0 or 1, the output is 0/-1, which is all
// sign bits set.
if (LZ == BitWidth - 1)
return BitWidth;
if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
ConstantRange X = getSignedRange(UDiv->getLHS());
ConstantRange Y = getSignedRange(UDiv->getRHS());
return X.udiv(Y);
}
// If we are subtracting one from a positive number, there is no carry
// out of the result.
if (LZ > 0)
return GetMinSignBits(OtherOpsAdd);
if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
ConstantRange X = getSignedRange(ZExt->getOperand());
return X.zeroExtend(cast<IntegerType>(ZExt->getType())->getBitWidth());
}
if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
ConstantRange X = getSignedRange(SExt->getOperand());
return X.signExtend(cast<IntegerType>(SExt->getType())->getBitWidth());
}
if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
ConstantRange X = getSignedRange(Trunc->getOperand());
return X.truncate(cast<IntegerType>(Trunc->getType())->getBitWidth());
}
ConstantRange FullSet(getTypeSizeInBits(S->getType()), true);
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
const SCEV *T = getBackedgeTakenCount(AddRec->getLoop());
const SCEVConstant *Trip = dyn_cast<SCEVConstant>(T);
if (!Trip) return FullSet;
// TODO: non-affine addrec
if (AddRec->isAffine()) {
const Type *Ty = AddRec->getType();
const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
if (getTypeSizeInBits(MaxBECount->getType()) <= getTypeSizeInBits(Ty)) {
MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
const SCEV *Start = AddRec->getStart();
const SCEV *Step = AddRec->getStepRecurrence(*this);
const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this);
// Check for overflow.
if (!(isKnownPositive(Step) &&
isKnownPredicate(ICmpInst::ICMP_SLT, Start, End)) &&
!(isKnownNegative(Step) &&
isKnownPredicate(ICmpInst::ICMP_SGT, Start, End)))
return FullSet;
ConstantRange StartRange = getSignedRange(Start);
ConstantRange EndRange = getSignedRange(End);
APInt Min = APIntOps::smin(StartRange.getSignedMin(),
EndRange.getSignedMin());
APInt Max = APIntOps::smax(StartRange.getSignedMax(),
EndRange.getSignedMax());
if (Min.isMinSignedValue() && Max.isMaxSignedValue())
return ConstantRange(Min.getBitWidth(), /*isFullSet=*/true);
return ConstantRange(Min, Max+1);
}
// Add can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
unsigned Min = BitWidth;
for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
unsigned N = GetMinSignBits(A->getOperand(i));
Min = std::min(Min, N) - 1;
if (Min == 0) return 1;
}
return 1;
}
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
// For a SCEVUnknown, ask ValueTracking.
return ComputeNumSignBits(U->getValue(), TD);
unsigned BitWidth = getTypeSizeInBits(U->getType());
unsigned NS = ComputeNumSignBits(U->getValue(), TD);
if (NS == 1)
return FullSet;
return
ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1);
}
return 1;
return FullSet;
}
/// createSCEV - We know that there is no SCEV for the specified value.
@ -3628,7 +3814,7 @@ const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
if (!isSCEVable(Op->getType()))
return V;
const SCEV *OpV = getSCEVAtScope(getSCEV(Op), L);
const SCEV* OpV = getSCEVAtScope(Op, L);
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV)) {
Constant *C = SC->getValue();
if (C->getType() != Op->getType())
@ -4029,12 +4215,176 @@ static bool HasSameValue(const SCEV *A, const SCEV *B) {
return false;
}
/// isLoopGuardedByCond - Test whether entry to the loop is protected by
/// a conditional between LHS and RHS. This is used to help avoid max
/// expressions in loop trip counts.
bool ScalarEvolution::isLoopGuardedByCond(const Loop *L,
ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS) {
bool ScalarEvolution::isKnownNegative(const SCEV *S) {
return getSignedRange(S).getSignedMax().isNegative();
}
bool ScalarEvolution::isKnownPositive(const SCEV *S) {
return getSignedRange(S).getSignedMin().isStrictlyPositive();
}
bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
return !getSignedRange(S).getSignedMin().isNegative();
}
bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
return !getSignedRange(S).getSignedMax().isStrictlyPositive();
}
bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
return isKnownNegative(S) || isKnownPositive(S);
}
bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS) {
if (HasSameValue(LHS, RHS))
return ICmpInst::isTrueWhenEqual(Pred);
switch (Pred) {
default:
assert(0 && "Unexpected ICmpInst::Predicate value!");
break;
case ICmpInst::ICMP_SGT:
Pred = ICmpInst::ICMP_SLT;
std::swap(LHS, RHS);
case ICmpInst::ICMP_SLT: {
ConstantRange LHSRange = getSignedRange(LHS);
ConstantRange RHSRange = getSignedRange(RHS);
if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
return true;
if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
return false;
const SCEV *Diff = getMinusSCEV(LHS, RHS);
ConstantRange DiffRange = getUnsignedRange(Diff);
if (isKnownNegative(Diff)) {
if (DiffRange.getUnsignedMax().ult(LHSRange.getUnsignedMin()))
return true;
if (DiffRange.getUnsignedMin().uge(LHSRange.getUnsignedMax()))
return false;
} else if (isKnownPositive(Diff)) {
if (LHSRange.getUnsignedMax().ult(DiffRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().uge(DiffRange.getUnsignedMax()))
return false;
}
break;
}
case ICmpInst::ICMP_SGE:
Pred = ICmpInst::ICMP_SLE;
std::swap(LHS, RHS);
case ICmpInst::ICMP_SLE: {
ConstantRange LHSRange = getSignedRange(LHS);
ConstantRange RHSRange = getSignedRange(RHS);
if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
return true;
if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
return false;
const SCEV *Diff = getMinusSCEV(LHS, RHS);
ConstantRange DiffRange = getUnsignedRange(Diff);
if (isKnownNonPositive(Diff)) {
if (DiffRange.getUnsignedMax().ule(LHSRange.getUnsignedMin()))
return true;
if (DiffRange.getUnsignedMin().ugt(LHSRange.getUnsignedMax()))
return false;
} else if (isKnownNonNegative(Diff)) {
if (LHSRange.getUnsignedMax().ule(DiffRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().ugt(DiffRange.getUnsignedMax()))
return false;
}
break;
}
case ICmpInst::ICMP_UGT:
Pred = ICmpInst::ICMP_ULT;
std::swap(LHS, RHS);
case ICmpInst::ICMP_ULT: {
ConstantRange LHSRange = getUnsignedRange(LHS);
ConstantRange RHSRange = getUnsignedRange(RHS);
if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
return false;
const SCEV *Diff = getMinusSCEV(LHS, RHS);
ConstantRange DiffRange = getUnsignedRange(Diff);
if (LHSRange.getUnsignedMax().ult(DiffRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().uge(DiffRange.getUnsignedMax()))
return false;
break;
}
case ICmpInst::ICMP_UGE:
Pred = ICmpInst::ICMP_ULE;
std::swap(LHS, RHS);
case ICmpInst::ICMP_ULE: {
ConstantRange LHSRange = getUnsignedRange(LHS);
ConstantRange RHSRange = getUnsignedRange(RHS);
if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
return false;
const SCEV *Diff = getMinusSCEV(LHS, RHS);
ConstantRange DiffRange = getUnsignedRange(Diff);
if (LHSRange.getUnsignedMax().ule(DiffRange.getUnsignedMin()))
return true;
if (LHSRange.getUnsignedMin().ugt(DiffRange.getUnsignedMax()))
return false;
break;
}
case ICmpInst::ICMP_NE: {
if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
return true;
if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
return true;
const SCEV *Diff = getMinusSCEV(LHS, RHS);
if (isKnownNonZero(Diff))
return true;
break;
}
case ICmpInst::ICMP_EQ:
break;
}
return false;
}
/// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
/// protected by a conditional between LHS and RHS. This is used to
/// to eliminate casts.
bool
ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS) {
// Interpret a null as meaning no loop, where there is obviously no guard
// (interprocedural conditions notwithstanding).
if (!L) return true;
BasicBlock *Latch = L->getLoopLatch();
if (!Latch)
return false;
BranchInst *LoopContinuePredicate =
dyn_cast<BranchInst>(Latch->getTerminator());
if (!LoopContinuePredicate ||
LoopContinuePredicate->isUnconditional())
return false;
return
isNecessaryCond(LoopContinuePredicate->getCondition(), Pred, LHS, RHS,
LoopContinuePredicate->getSuccessor(0) != L->getHeader());
}
/// isLoopGuardedByCond - Test whether entry to the loop is protected
/// by a conditional between LHS and RHS. This is used to help avoid max
/// expressions in loop trip counts, and to eliminate casts.
bool
ScalarEvolution::isLoopGuardedByCond(const Loop *L,
ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS) {
// Interpret a null as meaning no loop, where there is obviously no guard
// (interprocedural conditions notwithstanding).
if (!L) return false;
@ -4063,8 +4413,9 @@ bool ScalarEvolution::isLoopGuardedByCond(const Loop *L,
return false;
}
/// isNecessaryCond - Test whether the given CondValue value is a condition
/// which is at least as strict as the one described by Pred, LHS, and RHS.
/// isNecessaryCond - Test whether the condition described by Pred, LHS,
/// and RHS is a necessary condition for the given Cond value to evaluate
/// to true.
bool ScalarEvolution::isNecessaryCond(Value *CondValue,
ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
@ -4089,30 +4440,35 @@ bool ScalarEvolution::isNecessaryCond(Value *CondValue,
// see if it is the comparison we are looking for.
Value *PreCondLHS = ICI->getOperand(0);
Value *PreCondRHS = ICI->getOperand(1);
ICmpInst::Predicate Cond;
ICmpInst::Predicate FoundPred;
if (Inverse)
Cond = ICI->getInversePredicate();
FoundPred = ICI->getInversePredicate();
else
Cond = ICI->getPredicate();
FoundPred = ICI->getPredicate();
if (Cond == Pred)
if (FoundPred == Pred)
; // An exact match.
else if (!ICmpInst::isTrueWhenEqual(Cond) && Pred == ICmpInst::ICMP_NE)
; // The actual condition is beyond sufficient.
else
else if (!ICmpInst::isTrueWhenEqual(FoundPred) && Pred == ICmpInst::ICMP_NE) {
// The actual condition is beyond sufficient.
FoundPred = ICmpInst::ICMP_NE;
// NE is symmetric but the original comparison may not be. Swap
// the operands if necessary so that they match below.
if (isa<SCEVConstant>(LHS))
std::swap(PreCondLHS, PreCondRHS);
} else
// Check a few special cases.
switch (Cond) {
switch (FoundPred) {
case ICmpInst::ICMP_UGT:
if (Pred == ICmpInst::ICMP_ULT) {
std::swap(PreCondLHS, PreCondRHS);
Cond = ICmpInst::ICMP_ULT;
FoundPred = ICmpInst::ICMP_ULT;
break;
}
return false;
case ICmpInst::ICMP_SGT:
if (Pred == ICmpInst::ICMP_SLT) {
std::swap(PreCondLHS, PreCondRHS);
Cond = ICmpInst::ICMP_SLT;
FoundPred = ICmpInst::ICMP_SLT;
break;
}
return false;
@ -4121,8 +4477,8 @@ bool ScalarEvolution::isNecessaryCond(Value *CondValue,
// so check for this case by checking if the NE is comparing against
// a minimum or maximum constant.
if (!ICmpInst::isTrueWhenEqual(Pred))
if (ConstantInt *CI = dyn_cast<ConstantInt>(PreCondRHS)) {
const APInt &A = CI->getValue();
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(RHS)) {
const APInt &A = C->getValue()->getValue();
switch (Pred) {
case ICmpInst::ICMP_SLT:
if (A.isMaxSignedValue()) break;
@ -4139,7 +4495,7 @@ bool ScalarEvolution::isNecessaryCond(Value *CondValue,
default:
return false;
}
Cond = ICmpInst::ICMP_NE;
FoundPred = Pred;
// NE is symmetric but the original comparison may not be. Swap
// the operands if necessary so that they match below.
if (isa<SCEVConstant>(LHS))
@ -4152,14 +4508,73 @@ bool ScalarEvolution::isNecessaryCond(Value *CondValue,
return false;
}
if (!PreCondLHS->getType()->isInteger()) return false;
assert(Pred == FoundPred && "Conditions were not reconciled!");
const SCEV *PreCondLHSSCEV = getSCEV(PreCondLHS);
const SCEV *PreCondRHSSCEV = getSCEV(PreCondRHS);
return (HasSameValue(LHS, PreCondLHSSCEV) &&
HasSameValue(RHS, PreCondRHSSCEV)) ||
(HasSameValue(LHS, getNotSCEV(PreCondRHSSCEV)) &&
HasSameValue(RHS, getNotSCEV(PreCondLHSSCEV)));
// Bail if the ICmp's operands' types are wider than the needed type
// before attempting to call getSCEV on them. This avoids infinite
// recursion, since the analysis of widening casts can require loop
// exit condition information for overflow checking, which would
// lead back here.
if (getTypeSizeInBits(LHS->getType()) <
getTypeSizeInBits(PreCondLHS->getType()))
return false;
const SCEV *FoundLHS = getSCEV(PreCondLHS);
const SCEV *FoundRHS = getSCEV(PreCondRHS);
// Balance the types. The case where FoundLHS' type is wider than
// LHS' type is checked for above.
if (getTypeSizeInBits(LHS->getType()) >
getTypeSizeInBits(FoundLHS->getType())) {
if (CmpInst::isSigned(Pred)) {
FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
} else {
FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
}
}
return isNecessaryCondOperands(Pred, LHS, RHS,
FoundLHS, FoundRHS) ||
// ~x < ~y --> x > y
isNecessaryCondOperands(Pred, LHS, RHS,
getNotSCEV(FoundRHS), getNotSCEV(FoundLHS));
}
/// isNecessaryCondOperands - Test whether the condition described by Pred,
/// LHS, and RHS is a necessary condition for the condition described by
/// Pred, FoundLHS, and FoundRHS to evaluate to true.
bool
ScalarEvolution::isNecessaryCondOperands(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
const SCEV *FoundLHS,
const SCEV *FoundRHS) {
switch (Pred) {
default: break;
case ICmpInst::ICMP_SLT:
if (isKnownPredicate(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_SGE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_SGT:
if (isKnownPredicate(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_SLE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_ULT:
if (isKnownPredicate(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_UGE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_UGT:
if (isKnownPredicate(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_ULE, RHS, FoundRHS))
return true;
break;
}
return false;
}
/// getBECount - Subtract the end and start values and divide by the step,
@ -4180,9 +4595,9 @@ const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
// Check Add for unsigned overflow.
// TODO: More sophisticated things could be done here.
const Type *WideTy = Context->getIntegerType(getTypeSizeInBits(Ty) + 1);
const SCEV *OperandExtendedAdd =
getAddExpr(getZeroExtendExpr(Diff, WideTy),
getZeroExtendExpr(RoundUp, WideTy));
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();
@ -4244,9 +4659,9 @@ ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
const SCEV *Start = AddRec->getOperand(0);
// Determine the minimum constant start value.
const SCEV *MinStart = isa<SCEVConstant>(Start) ? Start :
getConstant(isSigned ? APInt::getSignedMinValue(BitWidth) :
APInt::getMinValue(BitWidth));
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
@ -4254,18 +4669,16 @@ ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
// the division must round up.
const SCEV *End = RHS;
if (!isLoopGuardedByCond(L,
isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
isSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT,
getMinusSCEV(Start, Step), RHS))
End = isSigned ? getSMaxExpr(RHS, Start)
: getUMaxExpr(RHS, Start);
// Determine the maximum constant end value.
const SCEV *MaxEnd =
isa<SCEVConstant>(End) ? End :
getConstant(isSigned ? APInt::getSignedMaxValue(BitWidth)
.ashr(GetMinSignBits(End) - 1) :
APInt::getMaxValue(BitWidth)
.lshr(GetMinLeadingZeros(End)));
const SCEV *MaxEnd = getConstant(isSigned ?
getSignedRange(End).getSignedMax() :
getUnsignedRange(End).getUnsignedMax());
// Finally, we subtract these two values and divide, rounding up, to get
// the number of times the backedge is executed.

1
test/Transforms/IndVarSimplify/iv-sext.ll
View File

@ -1,7 +1,6 @@
; RUN: llvm-as < %s | opt -indvars | llvm-dis > %t
; RUN: grep {= sext} %t | count 4
; RUN: grep {phi i64} %t | count 2
; XFAIL: *
; Indvars should be able to promote the hiPart induction variable in the
; inner loop to i64.