[APInt] Use isSubsetOf, intersects, and bit counting methods to reduce temporary APInts

[craig.topper]

Summary

This patch uses various APInt methods to reduce temporary APInt creation.

This should be all of the unrelated cleanups that got buried in D32376(creating a KnownBits struct) as well as some pointed out by Simon during the review of that. Plus a few improvements to use counting instead of masking.

I've left out any places where we do something like (KnownZero & KnownOne) != 0 as I plan to add a helper method to KnownBits to ask that question and didn't want to thrash that code an additional time.

[RKSimon]

LGTM - thanks Craig

lib/Analysis/InstructionSimplify.cpp

static Value *SimplifyShift(Instruction::BinaryOps Opcode, Value *Op0,
   APInt KnownOne(BitWidth, 0);
   computeKnownBits(Op1, KnownZero, KnownOne, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
   if (KnownOne.getLimitedValue() >= BitWidth)
     return UndefValue::get(Op0->getType());
 
   // If all valid bits in the shift amount are known zero, the first operand is
   // unchanged.
   unsigned NumValidShiftBits = Log2_32_Ceil(BitWidth);
-  APInt ShiftAmountMask = APInt::getLowBitsSet(BitWidth, NumValidShiftBits);
-  if ((KnownZero & ShiftAmountMask) == ShiftAmountMask)
+  if (KnownZero.countTrailingOnes() >= NumValidShiftBits)
     return Op0;
 
   return nullptr;
 }
 
 /// \brief Given operands for an Shl, LShr or AShr, see if we can
 /// fold the result.  If not, this returns null.
 static Value *SimplifyRightShift(Instruction::BinaryOps Opcode, Value *Op0,
static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   if (ICmpInst::isEquality(Pred)) {
     const APInt *RHSVal;
     if (match(RHS, m_APInt(RHSVal))) {
       unsigned BitWidth = RHSVal->getBitWidth();
       APInt LHSKnownZero(BitWidth, 0);
       APInt LHSKnownOne(BitWidth, 0);
       computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, Q.DL, /*Depth=*/0, Q.AC,
                        Q.CxtI, Q.DT);
-      if (((LHSKnownZero & *RHSVal) != 0) || ((LHSKnownOne & ~(*RHSVal)) != 0))
+      if (LHSKnownZero.intersects(*RHSVal) || !LHSKnownOne.isSubsetOf(*RHSVal))
         return Pred == ICmpInst::ICMP_EQ ? ConstantInt::getFalse(ITy)
                                          : ConstantInt::getTrue(ITy);
     }
   }
 
   // If the comparison is with the result of a select instruction, check whether
   // comparing with either branch of the select always yields the same value.
   if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))

lib/Analysis/ValueTracking.cpp

else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
     // zero unless both X and Y equal INT_MIN.
     if (BitWidth && XKnownNegative && YKnownNegative) {
       APInt KnownZero(BitWidth, 0);
       APInt KnownOne(BitWidth, 0);
       APInt Mask = APInt::getSignedMaxValue(BitWidth);
       // The sign bit of X is set.  If some other bit is set then X is not equal
       // to INT_MIN.
       computeKnownBits(X, KnownZero, KnownOne, Depth, Q);
-      if ((KnownOne & Mask) != 0)
+      if (KnownOne.intersects(Mask))
         return true;
       // The sign bit of Y is set.  If some other bit is set then Y is not equal
       // to INT_MIN.
       computeKnownBits(Y, KnownZero, KnownOne, Depth, Q);
-      if ((KnownOne & Mask) != 0)
+      if (KnownOne.intersects(Mask))
         return true;
     }
 
     // The sum of a non-negative number and a power of two is not zero.
     if (XKnownNonNegative &&
         isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
       return true;
     if (YKnownNonNegative &&

 /// type, and vectors of integers.  In the case
 /// where V is a vector, the mask, known zero, and known one values are the
 /// same width as the vector element, and the bit is set only if it is true
 /// for all of the elements in the vector.
 bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
                        const Query &Q) {
   APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0);
   computeKnownBits(V, KnownZero, KnownOne, Depth, Q);
-  return (KnownZero & Mask) == Mask;
+  return Mask.isSubsetOf(KnownZero);
 }
 
 /// For vector constants, loop over the elements and find the constant with the
 /// minimum number of sign bits. Return 0 if the value is not a vector constant
 /// or if any element was not analyzed; otherwise, return the count for the
 /// element with the minimum number of sign bits.
 static unsigned computeNumSignBitsVectorConstant(const Value *V,
                                                  unsigned TyBits) {
auto MatchNUWAddsToSameValue = [&](const Value *A, const Value *B,
 
       // If X & C == 0 then (X | C) == X +_{nuw} C
       if (match(A, m_Or(m_Value(X), m_APInt(CA))) &&
           match(B, m_Or(m_Specific(X), m_APInt(CB)))) {
         unsigned BitWidth = CA->getBitWidth();
         APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
         computeKnownBits(X, KnownZero, KnownOne, DL, Depth + 1, AC, CxtI, DT);
 
-        if ((KnownZero & *CA) == *CA && (KnownZero & *CB) == *CB)
+        if (CA->isSubsetOf(KnownZero) && CB->isSubsetOf(KnownZero))
           return true;
       }
 
       return false;
     };
 
     const Value *X;
     const APInt *CLHS, *CRHS;

lib/Transforms/InstCombine/InstCombineCalls.cpp

unsigned NumMaskBits = IsTZ ? KnownOne.countTrailingZeros()
                               : KnownOne.countLeadingZeros();
   APInt Mask = IsTZ ? APInt::getLowBitsSet(BitWidth, NumMaskBits)
                     : APInt::getHighBitsSet(BitWidth, NumMaskBits);
 
   // If all bits above (ctlz) or below (cttz) the first known one are known
   // zero, this value is constant.
   // FIXME: This should be in InstSimplify because we're replacing an
   // instruction with a constant.
-  if ((Mask & KnownZero) == Mask) {
+  if (Mask.isSubsetOf(KnownZero)) {
     auto *C = ConstantInt::get(IT, APInt(BitWidth, NumMaskBits));
     return IC.replaceInstUsesWith(II, C);
   }
 
   // If the input to cttz/ctlz is known to be non-zero,
   // then change the 'ZeroIsUndef' parameter to 'true'
   // because we know the zero behavior can't affect the result.
   if (KnownOne != 0 || isKnownNonZero(Op0, IC.getDataLayout())) {

lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

if (NLZ > 0) {
         BinaryOperator &BinOP = *cast<BinaryOperator>(I);
         BinOP.setHasNoSignedWrap(false);
         BinOP.setHasNoUnsignedWrap(false);
         return I;
       }
 
       // If we are known to be adding/subtracting zeros to every bit below
       // the highest demanded bit, we just return the other side.
-      if ((DemandedFromOps & RHSKnownZero) == DemandedFromOps)
+      if (DemandedFromOps.isSubsetOf(RHSKnownZero))
         return I->getOperand(0);
       // We can't do this with the LHS for subtraction.
       if (I->getOpcode() == Instruction::Add &&
-          (DemandedFromOps & LHSKnownZero) == DemandedFromOps)
+          DemandedFromOps.isSubsetOf(LHSKnownZero))
         return I->getOperand(1);
     }
 
     // Otherwise just hand the add/sub off to computeKnownBits to fill in
     // the known zeros and ones.
     computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI);
     break;
   }

lib/Transforms/Utils/SimplifyCFG.cpp

static bool EliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC,
   // bits are in the condition value.
   unsigned ExtraSignBits = ComputeNumSignBits(Cond, DL, 0, AC, SI) - 1;
   unsigned MaxSignificantBitsInCond = Bits - ExtraSignBits;
 
   // Gather dead cases.
   SmallVector<ConstantInt *, 8> DeadCases;
   for (auto &Case : SI->cases()) {
     APInt CaseVal = Case.getCaseValue()->getValue();
-    if ((CaseVal & KnownZero) != 0 || (CaseVal & KnownOne) != KnownOne ||
+    if (KnownZero.intersects(CaseVal) || !KnownOne.isSubsetOf(CaseVal) ||
         (CaseVal.getMinSignedBits() > MaxSignificantBitsInCond)) {
       DeadCases.push_back(Case.getCaseValue());
       DEBUG(dbgs() << "SimplifyCFG: switch case " << CaseVal << " is dead.\n");
     }
   }
 
   // If we can prove that the cases must cover all possible values, the
   // default destination becomes dead and we can remove it.  If we know some

lib/Transforms/Vectorize/LoadStoreVectorizer.cpp

bool Vectorizer::isConsecutiveAccess(Value *A, Value *B) {
 
   // Second attempt:
   // If any bits are known to be zero other than the sign bit in OpA, we can
   // add 1 to it while guaranteeing no overflow of any sort.
   if (!Safe) {
     APInt KnownZero(BitWidth, 0);
     APInt KnownOne(BitWidth, 0);
     computeKnownBits(OpA, KnownZero, KnownOne, DL, 0, nullptr, OpA, &DT);
-    KnownZero &= ~APInt::getHighBitsSet(BitWidth, 1);
-    if (KnownZero != 0)
+    if (KnownZero.countTrailingZeros() < (BitWidth - 1))
       Safe = true;
   }
 
   if (!Safe)
     return false;
 
   const SCEV *OffsetSCEVA = SE.getSCEV(OpA);
   const SCEV *OffsetSCEVB = SE.getSCEV(OpB);