[CodeGen] Use APInt::setLowBits/setHighBits/setBitsFrom in more places

[craig.topper]

Summary

This patch replaces ORs with getHighBits/getLowBits etc. with setLowBits/setHighBits/setBitsFrom.

In a few of the places we weren't ORing, but the KnownZero/KnownOne vectors were already initialized to zero. We exploit this in most places already there were just some that were inconsistent.

[davide]

lgtm

llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

case ISD::MUL: {
     // interesting case of alignment computation.
     KnownOne.clearAllBits();
     unsigned TrailZ = KnownZero.countTrailingOnes() +
                       KnownZero2.countTrailingOnes();
     unsigned LeadZ =  std::max(KnownZero.countLeadingOnes() +
                                KnownZero2.countLeadingOnes(),
                                BitWidth) - BitWidth;
 
-    TrailZ = std::min(TrailZ, BitWidth);
-    LeadZ = std::min(LeadZ, BitWidth);
-    KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
-                APInt::getHighBitsSet(BitWidth, LeadZ);
+    KnownZero.clearAllBits();
+    KnownZero.setLowBits(std::min(TrailZ, BitWidth));
+    KnownZero.setHighBits(std::min(LeadZ, BitWidth));
     break;
   }
   case ISD::UDIV: {
     // For the purposes of computing leading zeros we can conservatively
     // treat a udiv as a logical right shift by the power of 2 known to
     // be less than the denominator.
     computeKnownBits(Op.getOperand(0), KnownZero2, KnownOne2, DemandedElts,
                      Depth + 1);
     unsigned LeadZ = KnownZero2.countLeadingOnes();
 
     computeKnownBits(Op.getOperand(1), KnownZero2, KnownOne2, DemandedElts,
                      Depth + 1);
     unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros();
     if (RHSUnknownLeadingOnes != BitWidth)
       LeadZ = std::min(BitWidth,
                        LeadZ + BitWidth - RHSUnknownLeadingOnes - 1);
 
-    KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ);
+    KnownZero.setHighBits(LeadZ);
     break;
   }
   case ISD::SELECT:
     computeKnownBits(Op.getOperand(2), KnownZero, KnownOne, Depth+1);
     // If we don't know any bits, early out.
     if (!KnownOne && !KnownZero)
       break;
     computeKnownBits(Op.getOperand(1), KnownZero2, KnownOne2, Depth+1);
void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
   case ISD::SRA:
     if (const APInt *ShAmt = getValidShiftAmountConstant(Op)) {
       computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, DemandedElts,
                        Depth + 1);
       KnownZero = KnownZero.lshr(*ShAmt);
       KnownOne  = KnownOne.lshr(*ShAmt);
       // If we know the value of the sign bit, then we know it is copied across
       // the high bits by the shift amount.
-      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt->getZExtValue());
       APInt SignBit = APInt::getSignBit(BitWidth);
       SignBit = SignBit.lshr(*ShAmt);  // Adjust to where it is now in the mask.
       if (KnownZero.intersects(SignBit)) {
-        KnownZero |= HighBits;  // New bits are known zero.
+        KnownZero.setHighBits(ShAmt->getZExtValue());// New bits are known zero.
       } else if (KnownOne.intersects(SignBit)) {
-        KnownOne  |= HighBits;  // New bits are known one.
+        KnownOne.setHighBits(ShAmt->getZExtValue()); // New bits are known one.
       }
     }
     break;
   case ISD::SIGN_EXTEND_INREG: {
     EVT EVT = cast<VTSDNode>(Op.getOperand(1))->getVT();
     unsigned EBits = EVT.getScalarSizeInBits();
 
     // Sign extension.  Compute the demanded bits in the result that are not
case ISD::SIGN_EXTEND_INREG: {
     }
     break;
   }
   case ISD::CTTZ:
   case ISD::CTTZ_ZERO_UNDEF:
   case ISD::CTLZ:
   case ISD::CTLZ_ZERO_UNDEF:
   case ISD::CTPOP: {
-    unsigned LowBits = Log2_32(BitWidth)+1;
-    KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
-    KnownOne.clearAllBits();
+    KnownZero.setBitsFrom(Log2_32(BitWidth)+1);
     break;
   }
   case ISD::LOAD: {
     LoadSDNode *LD = cast<LoadSDNode>(Op);
     // If this is a ZEXTLoad and we are looking at the loaded value.
     if (ISD::isZEXTLoad(Op.getNode()) && Op.getResNo() == 0) {
       EVT VT = LD->getMemoryVT();
       unsigned MemBits = VT.getScalarSizeInBits();
-      KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
+      KnownZero.setBitsFrom(MemBits);
     } else if (const MDNode *Ranges = LD->getRanges()) {
       if (LD->getExtensionType() == ISD::NON_EXTLOAD)
         computeKnownBitsFromRangeMetadata(*Ranges, KnownZero, KnownOne);
     }
     break;
   }
   case ISD::ZERO_EXTEND_VECTOR_INREG: {
     EVT InVT = Op.getOperand(0).getValueType();
     unsigned InBits = InVT.getScalarSizeInBits();
-    APInt NewBits   = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);
     KnownZero = KnownZero.trunc(InBits);
     KnownOne = KnownOne.trunc(InBits);
     computeKnownBits(Op.getOperand(0), KnownZero, KnownOne,
                      DemandedElts.zext(InVT.getVectorNumElements()),
                      Depth + 1);
     KnownZero = KnownZero.zext(BitWidth);
     KnownOne = KnownOne.zext(BitWidth);
-    KnownZero |= NewBits;
+    KnownZero.setBitsFrom(InBits);
     break;
   }
   case ISD::ZERO_EXTEND: {
     EVT InVT = Op.getOperand(0).getValueType();
     unsigned InBits = InVT.getScalarSizeInBits();
-    APInt NewBits   = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);
     KnownZero = KnownZero.trunc(InBits);
     KnownOne = KnownOne.trunc(InBits);
     computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, DemandedElts,
                      Depth + 1);
     KnownZero = KnownZero.zext(BitWidth);
     KnownOne = KnownOne.zext(BitWidth);
-    KnownZero |= NewBits;
+    KnownZero.setBitsFrom(InBits);
     break;
   }
   // TODO ISD::SIGN_EXTEND_VECTOR_INREG
   case ISD::SIGN_EXTEND: {
     EVT InVT = Op.getOperand(0).getValueType();
     unsigned InBits = InVT.getScalarSizeInBits();
 
     KnownZero = KnownZero.trunc(InBits);
case ISD::AssertZext: {
     APInt InMask = APInt::getLowBitsSet(BitWidth, VT.getSizeInBits());
     computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
     KnownZero |= (~InMask);
     KnownOne  &= (~KnownZero);
     break;
   }
   case ISD::FGETSIGN:
     // All bits are zero except the low bit.
-    KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - 1);
+    KnownZero.setBitsFrom(1);
     break;
   case ISD::USUBO:
   case ISD::SSUBO:
     if (Op.getResNo() == 1) {
       // If we know the result of a setcc has the top bits zero, use this info.
       if (TLI->getBooleanContents(Op.getOperand(0).getValueType()) ==
               TargetLowering::ZeroOrOneBooleanContent &&
           BitWidth > 1)
if (ConstantSDNode *CLHS = isConstOrConstSplat(Op.getOperand(0))) {
                          Depth + 1);
 
         // If all of the MaskV bits are known to be zero, then we know the
         // output top bits are zero, because we now know that the output is
         // from [0-C].
         if ((KnownZero2 & MaskV) == MaskV) {
           unsigned NLZ2 = CLHS->getAPIntValue().countLeadingZeros();
           // Top bits known zero.
-          KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2);
+          KnownZero.setHighBits(NLZ2);
         }
       }
     }
 
     // If low bits are know to be zero in both operands, then we know they are
     // going to be 0 in the result. Both addition and complement operations
     // preserve the low zero bits.
     computeKnownBits(Op.getOperand(0), KnownZero2, KnownOne2, DemandedElts,
case ISD::UREM: {
     computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, DemandedElts,
                      Depth + 1);
     computeKnownBits(Op.getOperand(1), KnownZero2, KnownOne2, DemandedElts,
                      Depth + 1);
 
     uint32_t Leaders = std::max(KnownZero.countLeadingOnes(),
                                 KnownZero2.countLeadingOnes());
     KnownOne.clearAllBits();
-    KnownZero = APInt::getHighBitsSet(BitWidth, Leaders);
+    KnownZero.clearAllBits();
+    KnownZero.setHighBits(Leaders);
     break;
   }
   case ISD::EXTRACT_ELEMENT: {
     computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
     const unsigned Index = Op.getConstantOperandVal(1);
     const unsigned BitWidth = Op.getValueSizeInBits();
 
     // Remove low part of known bits mask
case ISD::SMAX: {
     KnownZero &= KnownZero2;
     KnownOne &= KnownOne2;
     break;
   }
   case ISD::FrameIndex:
   case ISD::TargetFrameIndex:
     if (unsigned Align = InferPtrAlignment(Op)) {
       // The low bits are known zero if the pointer is aligned.
-      KnownZero = APInt::getLowBitsSet(BitWidth, Log2_32(Align));
+      KnownZero.setLowBits(Log2_32(Align));
       break;
     }
     break;
 
   default:
     if (Opcode < ISD::BUILTIN_OP_END)
       break;
     LLVM_FALLTHROUGH;

llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
                                                      NewExt, NewSA));
           }
         }
       }
 
       KnownZero <<= SA->getZExtValue();
       KnownOne  <<= SA->getZExtValue();
       // low bits known zero.
-      KnownZero |= APInt::getLowBitsSet(BitWidth, SA->getZExtValue());
+      KnownZero.setLowBits(SA->getZExtValue());
     }
     break;
   case ISD::SRL:
     if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
       EVT VT = Op.getValueType();
       unsigned ShAmt = SA->getZExtValue();
       unsigned VTSize = VT.getSizeInBits();
       SDValue InOp = Op.getOperand(0);
 
       // If the shift count is an invalid immediate, don't do anything.
       if (ShAmt >= BitWidth)
         break;
 
       APInt InDemandedMask = (NewMask << ShAmt);
 
       // If the shift is exact, then it does demand the low bits (and knows that
       // they are zero).
       if (cast<BinaryWithFlagsSDNode>(Op)->Flags.hasExact())
-        InDemandedMask |= APInt::getLowBitsSet(BitWidth, ShAmt);
+        InDemandedMask.setLowBits(ShAmt);
 
       // If this is ((X << C1) >>u ShAmt), see if we can simplify this into a
       // single shift.  We can do this if the top bits (which are shifted out)
       // are never demanded.
       if (InOp.getOpcode() == ISD::SHL &&
           isa<ConstantSDNode>(InOp.getOperand(1))) {
         if (ShAmt && (NewMask & APInt::getHighBitsSet(VTSize, ShAmt)) == 0) {
           unsigned C1= cast<ConstantSDNode>(InOp.getOperand(1))->getZExtValue();
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
       // Compute the new bits that are at the top now.
       if (SimplifyDemandedBits(InOp, InDemandedMask,
                                KnownZero, KnownOne, TLO, Depth+1))
         return true;
       assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
       KnownZero = KnownZero.lshr(ShAmt);
       KnownOne  = KnownOne.lshr(ShAmt);
 
-      APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);
-      KnownZero |= HighBits;  // High bits known zero.
+      KnownZero.setHighBits(ShAmt);  // High bits known zero.
     }
     break;
   case ISD::SRA:
     // If this is an arithmetic shift right and only the low-bit is set, we can
     // always convert this into a logical shr, even if the shift amount is
     // variable.  The low bit of the shift cannot be an input sign bit unless
     // the shift amount is >= the size of the datatype, which is undefined.
     if (NewMask == 1)
if (ConstantSDNode *SA = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
       if (ShAmt >= BitWidth)
         break;
 
       APInt InDemandedMask = (NewMask << ShAmt);
 
       // If the shift is exact, then it does demand the low bits (and knows that
       // they are zero).
       if (cast<BinaryWithFlagsSDNode>(Op)->Flags.hasExact())
-        InDemandedMask |= APInt::getLowBitsSet(BitWidth, ShAmt);
+        InDemandedMask.setLowBits(ShAmt);
 
       // If any of the demanded bits are produced by the sign extension, we also
       // demand the input sign bit.
       APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt);
       if (HighBits.intersects(NewMask))
         InDemandedMask |= APInt::getSignBit(VT.getScalarSizeInBits());
 
       if (SimplifyDemandedBits(Op.getOperand(0), InDemandedMask,