// If the index is larger than the pointer size of the target, truncate the
// index down like the GEP would do implicitly. We don't have to do this for
// an inbounds GEP because the index can't be out of range.
- if (!GEP->isInBounds() &&
- Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits())
- Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext()));
+ if (!GEP->isInBounds()) {
+ Type *IntPtrTy = TD->getIntPtrType(GEP->getType());
+ unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
+ if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
+ Idx = Builder->CreateTrunc(Idx, IntPtrTy);
+ }
// If the comparison is only true for one or two elements, emit direct
// comparisons.
}
}
+
+
// Okay, we know we have a single variable index, which must be a
// pointer/array/vector index. If there is no offset, life is simple, return
// the index.
- unsigned IntPtrWidth = TD.getPointerSizeInBits();
+ Type *IntPtrTy = TD.getIntPtrType(GEP->getOperand(0)->getType());
+ unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
if (Offset == 0) {
// Cast to intptrty in case a truncation occurs. If an extension is needed,
// we don't need to bother extending: the extension won't affect where the
// computation crosses zero.
if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
- Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy);
}
return VariableIdx;
return 0;
// Okay, we can do this evaluation. Start by converting the index to intptr.
- Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
if (VariableIdx->getType() != IntPtrTy)
VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy,
true /*Signed*/);
}
/// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X".
-Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI,
+Instruction *InstCombiner::FoldICmpAddOpCst(Instruction &ICI,
Value *X, ConstantInt *CI,
- ICmpInst::Predicate Pred,
- Value *TheAdd) {
+ ICmpInst::Predicate Pred) {
// If we have X+0, exit early (simplifying logic below) and let it get folded
// elsewhere. icmp X+0, X -> icmp X, X
if (CI->isZero()) {
}
break;
- case Instruction::Xor: // (icmp pred (xor X, XorCST), CI)
- if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
+ case Instruction::Xor: // (icmp pred (xor X, XorCst), CI)
+ if (ConstantInt *XorCst = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// If this is a comparison that tests the signbit (X < 0) or (x > -1),
// fold the xor.
if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) ||
(ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) {
Value *CompareVal = LHSI->getOperand(0);
- // If the sign bit of the XorCST is not set, there is no change to
+ // If the sign bit of the XorCst is not set, there is no change to
// the operation, just stop using the Xor.
- if (!XorCST->isNegative()) {
+ if (!XorCst->isNegative()) {
ICI.setOperand(0, CompareVal);
Worklist.Add(LHSI);
return &ICI;
if (LHSI->hasOneUse()) {
// (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit))
- if (!ICI.isEquality() && XorCST->getValue().isSignBit()) {
- const APInt &SignBit = XorCST->getValue();
+ if (!ICI.isEquality() && XorCst->getValue().isSignBit()) {
+ const APInt &SignBit = XorCst->getValue();
ICmpInst::Predicate Pred = ICI.isSigned()
? ICI.getUnsignedPredicate()
: ICI.getSignedPredicate();
}
// (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A)
- if (!ICI.isEquality() && XorCST->isMaxValue(true)) {
- const APInt &NotSignBit = XorCST->getValue();
+ if (!ICI.isEquality() && XorCst->isMaxValue(true)) {
+ const APInt &NotSignBit = XorCst->getValue();
ICmpInst::Predicate Pred = ICI.isSigned()
? ICI.getUnsignedPredicate()
: ICI.getSignedPredicate();
// (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
// iff -C is a power of 2
if (ICI.getPredicate() == ICmpInst::ICMP_UGT &&
- XorCST->getValue() == ~RHSV && (RHSV + 1).isPowerOf2())
- return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), XorCST);
+ XorCst->getValue() == ~RHSV && (RHSV + 1).isPowerOf2())
+ return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), XorCst);
// (icmp ult (xor X, C), -C) -> (icmp uge X, C)
// iff -C is a power of 2
if (ICI.getPredicate() == ICmpInst::ICMP_ULT &&
- XorCST->getValue() == -RHSV && RHSV.isPowerOf2())
- return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), XorCST);
+ XorCst->getValue() == -RHSV && RHSV.isPowerOf2())
+ return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), XorCst);
}
break;
- case Instruction::And: // (icmp pred (and X, AndCST), RHS)
+ case Instruction::And: // (icmp pred (and X, AndCst), RHS)
if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
LHSI->getOperand(0)->hasOneUse()) {
- ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
+ ConstantInt *AndCst = cast<ConstantInt>(LHSI->getOperand(1));
// If the LHS is an AND of a truncating cast, we can widen the
// and/compare to be the input width without changing the value
// Extending a relational comparison when we're checking the sign
// bit would not work.
if (ICI.isEquality() ||
- (!AndCST->isNegative() && RHSV.isNonNegative())) {
+ (!AndCst->isNegative() && RHSV.isNonNegative())) {
Value *NewAnd =
Builder->CreateAnd(Cast->getOperand(0),
- ConstantExpr::getZExt(AndCST, Cast->getSrcTy()));
+ ConstantExpr::getZExt(AndCst, Cast->getSrcTy()));
NewAnd->takeName(LHSI);
return new ICmpInst(ICI.getPredicate(), NewAnd,
ConstantExpr::getZExt(RHS, Cast->getSrcTy()));
if (ICI.isEquality() && RHSV.getActiveBits() <= Ty->getBitWidth()) {
Value *NewAnd =
Builder->CreateAnd(Cast->getOperand(0),
- ConstantExpr::getTrunc(AndCST, Ty));
+ ConstantExpr::getTrunc(AndCst, Ty));
NewAnd->takeName(LHSI);
return new ICmpInst(ICI.getPredicate(), NewAnd,
ConstantExpr::getTrunc(RHS, Ty));
ConstantInt *ShAmt;
ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0;
- Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift.
- Type *AndTy = AndCST->getType(); // Type of the and.
- // We can fold this as long as we can't shift unknown bits
- // into the mask. This can only happen with signed shift
- // rights, as they sign-extend.
+ // This seemingly simple opportunity to fold away a shift turns out to
+ // be rather complicated. See PR17827
+ // ( http://llvm.org/bugs/show_bug.cgi?id=17827 ) for details.
if (ShAmt) {
- bool CanFold = Shift->isLogicalShift();
- if (!CanFold) {
- // To test for the bad case of the signed shr, see if any
- // of the bits shifted in could be tested after the mask.
- uint32_t TyBits = Ty->getPrimitiveSizeInBits();
- int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits);
-
- uint32_t BitWidth = AndTy->getPrimitiveSizeInBits();
- if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) &
- AndCST->getValue()) == 0)
+ bool CanFold = false;
+ unsigned ShiftOpcode = Shift->getOpcode();
+ if (ShiftOpcode == Instruction::AShr) {
+ // There may be some constraints that make this possible,
+ // but nothing simple has been discovered yet.
+ CanFold = false;
+ } else if (ShiftOpcode == Instruction::Shl) {
+ // For a left shift, we can fold if the comparison is not signed.
+ // We can also fold a signed comparison if the mask value and
+ // comparison value are not negative. These constraints may not be
+ // obvious, but we can prove that they are correct using an SMT
+ // solver such as "Z3" :
+ // http://rise4fun.com/Z3/DyMp
+ if (!ICI.isSigned() || (!AndCst->isNegative() && !RHS->isNegative()))
CanFold = true;
+ } else if (ShiftOpcode == Instruction::LShr) {
+ // For a logical right shift, we can fold if the comparison is not
+ // signed. We can also fold a signed comparison if the shifted mask
+ // value and the shifted comparison value are not negative.
+ // These constraints may not be obvious, but we can prove that they
+ // are correct using an SMT solver such as "Z3" :
+ // http://rise4fun.com/Z3/Tslfh
+ if (!ICI.isSigned())
+ CanFold = true;
+ else {
+ ConstantInt *ShiftedAndCst =
+ cast<ConstantInt>(ConstantExpr::getShl(AndCst, ShAmt));
+ ConstantInt *ShiftedRHSCst =
+ cast<ConstantInt>(ConstantExpr::getShl(RHS, ShAmt));
+
+ if (!ShiftedAndCst->isNegative() && !ShiftedRHSCst->isNegative())
+ CanFold = true;
+ }
}
if (CanFold) {
Constant *NewCst;
- if (Shift->getOpcode() == Instruction::Shl)
+ if (ShiftOpcode == Instruction::Shl)
NewCst = ConstantExpr::getLShr(RHS, ShAmt);
else
NewCst = ConstantExpr::getShl(RHS, ShAmt);
// Check to see if we are shifting out any of the bits being
// compared.
- if (ConstantExpr::get(Shift->getOpcode(),
- NewCst, ShAmt) != RHS) {
+ if (ConstantExpr::get(ShiftOpcode, NewCst, ShAmt) != RHS) {
// If we shifted bits out, the fold is not going to work out.
// As a special case, check to see if this means that the
// result is always true or false now.
return ReplaceInstUsesWith(ICI, Builder->getTrue());
} else {
ICI.setOperand(1, NewCst);
- Constant *NewAndCST;
- if (Shift->getOpcode() == Instruction::Shl)
- NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt);
+ Constant *NewAndCst;
+ if (ShiftOpcode == Instruction::Shl)
+ NewAndCst = ConstantExpr::getLShr(AndCst, ShAmt);
else
- NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
- LHSI->setOperand(1, NewAndCST);
+ NewAndCst = ConstantExpr::getShl(AndCst, ShAmt);
+ LHSI->setOperand(1, NewAndCst);
LHSI->setOperand(0, Shift->getOperand(0));
Worklist.Add(Shift); // Shift is dead.
return &ICI;
// Compute C << Y.
Value *NS;
if (Shift->getOpcode() == Instruction::LShr) {
- NS = Builder->CreateShl(AndCST, Shift->getOperand(1));
+ NS = Builder->CreateShl(AndCst, Shift->getOperand(1));
} else {
// Insert a logical shift.
- NS = Builder->CreateLShr(AndCST, Shift->getOperand(1));
+ NS = Builder->CreateLShr(AndCst, Shift->getOperand(1));
}
// Compute X & (C << Y).
return &ICI;
}
- // Replace ((X & AndCST) > RHSV) with ((X & AndCST) != 0), if any
- // bit set in (X & AndCST) will produce a result greater than RHSV.
+ // Replace ((X & AndCst) > RHSV) with ((X & AndCst) != 0), if any
+ // bit set in (X & AndCst) will produce a result greater than RHSV.
if (ICI.getPredicate() == ICmpInst::ICMP_UGT) {
- unsigned NTZ = AndCST->getValue().countTrailingZeros();
- if ((NTZ < AndCST->getBitWidth()) &&
- APInt::getOneBitSet(AndCST->getBitWidth(), NTZ).ugt(RHSV))
+ unsigned NTZ = AndCst->getValue().countTrailingZeros();
+ if ((NTZ < AndCst->getBitWidth()) &&
+ APInt::getOneBitSet(AndCst->getBitWidth(), NTZ).ugt(RHSV))
return new ICmpInst(ICmpInst::ICMP_NE, LHSI,
Constant::getNullValue(RHS->getType()));
}
// Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
// integer type is the same size as the pointer type.
if (TD && LHSCI->getOpcode() == Instruction::PtrToInt &&
- TD->getPointerSizeInBits() ==
- cast<IntegerType>(DestTy)->getBitWidth()) {
+ TD->getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
Value *RHSOp = 0;
if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
}
+/// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
+/// should be swapped.
+/// The descision is based on how many times these two operands are reused
+/// as subtract operands and their positions in those instructions.
+/// The rational is that several architectures use the same instruction for
+/// both subtract and cmp, thus it is better if the order of those operands
+/// match.
+/// \return true if Op0 and Op1 should be swapped.
+static bool swapMayExposeCSEOpportunities(const Value * Op0,
+ const Value * Op1) {
+ // Filter out pointer value as those cannot appears directly in subtract.
+ // FIXME: we may want to go through inttoptrs or bitcasts.
+ if (Op0->getType()->isPointerTy())
+ return false;
+ // Count every uses of both Op0 and Op1 in a subtract.
+ // Each time Op0 is the first operand, count -1: swapping is bad, the
+ // subtract has already the same layout as the compare.
+ // Each time Op0 is the second operand, count +1: swapping is good, the
+ // subtract has a diffrent layout as the compare.
+ // At the end, if the benefit is greater than 0, Op0 should come second to
+ // expose more CSE opportunities.
+ int GlobalSwapBenefits = 0;
+ for (Value::const_use_iterator UI = Op0->use_begin(), UIEnd = Op0->use_end(); UI != UIEnd; ++UI) {
+ const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(*UI);
+ if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
+ continue;
+ // If Op0 is the first argument, this is not beneficial to swap the
+ // arguments.
+ int LocalSwapBenefits = -1;
+ unsigned Op1Idx = 1;
+ if (BinOp->getOperand(Op1Idx) == Op0) {
+ Op1Idx = 0;
+ LocalSwapBenefits = 1;
+ }
+ if (BinOp->getOperand(Op1Idx) != Op1)
+ continue;
+ GlobalSwapBenefits += LocalSwapBenefits;
+ }
+ return GlobalSwapBenefits > 0;
+}
+
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool Changed = false;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ unsigned Op0Cplxity = getComplexity(Op0);
+ unsigned Op1Cplxity = getComplexity(Op1);
/// Orders the operands of the compare so that they are listed from most
/// complex to least complex. This puts constants before unary operators,
/// before binary operators.
- if (getComplexity(Op0) < getComplexity(Op1)) {
+ if (Op0Cplxity < Op1Cplxity ||
+ (Op0Cplxity == Op1Cplxity &&
+ swapMayExposeCSEOpportunities(Op0, Op1))) {
I.swapOperands();
std::swap(Op0, Op1);
Changed = true;
case Instruction::IntToPtr:
// icmp pred inttoptr(X), null -> icmp pred X, 0
if (RHSC->isNullValue() && TD &&
- TD->getIntPtrType(RHSC->getContext()) ==
+ TD->getIntPtrType(RHSC->getType()) ==
LHSI->getOperand(0)->getType())
return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
Constant::getNullValue(LHSI->getOperand(0)->getType()));
Builder->CreateTrunc(B, A->getType()));
}
+ // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
+ // For lshr and ashr pairs.
+ if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
+ match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
+ (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
+ match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
+ unsigned TypeBits = Cst1->getBitWidth();
+ unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
+ if (ShAmt < TypeBits && ShAmt != 0) {
+ ICmpInst::Predicate Pred = I.getPredicate() == ICmpInst::ICMP_NE
+ ? ICmpInst::ICMP_UGE
+ : ICmpInst::ICMP_ULT;
+ Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted");
+ APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
+ return new ICmpInst(Pred, Xor, Builder->getInt(CmpVal));
+ }
+ }
+
// Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
// "icmp (and X, mask), cst"
uint64_t ShAmt = 0;
Value *X; ConstantInt *Cst;
// icmp X+Cst, X
if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
- return FoldICmpAddOpCst(I, X, Cst, I.getPredicate(), Op0);
+ return FoldICmpAddOpCst(I, X, Cst, I.getPredicate());
// icmp X, X+Cst
if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
- return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1);
+ return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate());
}
return Changed ? &I : 0;
}
-
-
-
-
-
/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
///
Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,