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[SelectionDAG] Simplify the ISD::SIGN_EXTEND/ZERO_EXTEND handling to use less temporary APInts by counting bits instead. NFCI 

llvm-svn: 315628
This commit is contained in:
Craig Topper 2017-10-12 21:58:25 +00:00
parent ad5997e87a
commit d52cf99f53
1 changed files with 11 additions and 25 deletions
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36
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -1079,61 +1079,47 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
} }
case ISD::ZERO_EXTEND: { case ISD::ZERO_EXTEND: {
unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits(); unsigned OperandBitWidth = Op.getOperand(0).getScalarValueSizeInBits();
APInt InMask = NewMask.trunc(OperandBitWidth);
// If none of the top bits are demanded, convert this into an any_extend. // If none of the top bits are demanded, convert this into an any_extend.
APInt NewBits = if (NewMask.getActiveBits() <= OperandBitWidth)
APInt::getHighBitsSet(BitWidth, BitWidth - OperandBitWidth) & NewMask;
if (!NewBits.intersects(NewMask))
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND, dl, return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND, dl,
Op.getValueType(), Op.getValueType(),
Op.getOperand(0))); Op.getOperand(0)));
APInt InMask = NewMask.trunc(OperandBitWidth);
if (SimplifyDemandedBits(Op.getOperand(0), InMask, Known, TLO, Depth+1)) if (SimplifyDemandedBits(Op.getOperand(0), InMask, Known, TLO, Depth+1))
return true; return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?"); assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known = Known.zext(BitWidth); Known = Known.zext(BitWidth);
Known.Zero |= NewBits; Known.Zero.setBitsFrom(OperandBitWidth);
break; break;
} }
case ISD::SIGN_EXTEND: { case ISD::SIGN_EXTEND: {
EVT InVT = Op.getOperand(0).getValueType(); unsigned InBits = Op.getOperand(0).getValueType().getScalarSizeInBits();
unsigned InBits = InVT.getScalarSizeInBits();
APInt InMask = APInt::getLowBitsSet(BitWidth, InBits);
APInt InSignBit = APInt::getOneBitSet(BitWidth, InBits - 1);
APInt NewBits = ~InMask & NewMask;
// If none of the top bits are demanded, convert this into an any_extend. // If none of the top bits are demanded, convert this into an any_extend.
if (NewBits == 0) if (NewMask.getActiveBits() <= InBits)
return TLO.CombineTo(Op,TLO.DAG.getNode(ISD::ANY_EXTEND, dl, return TLO.CombineTo(Op,TLO.DAG.getNode(ISD::ANY_EXTEND, dl,
Op.getValueType(), Op.getValueType(),
Op.getOperand(0))); Op.getOperand(0)));
// Since some of the sign extended bits are demanded, we know that the sign // Since some of the sign extended bits are demanded, we know that the sign
// bit is demanded. // bit is demanded.
APInt InDemandedBits = InMask & NewMask; APInt InDemandedBits = NewMask.trunc(InBits);
InDemandedBits |= InSignBit; InDemandedBits.setBit(InBits - 1);
InDemandedBits = InDemandedBits.trunc(InBits);
if (SimplifyDemandedBits(Op.getOperand(0), InDemandedBits, Known, TLO, if (SimplifyDemandedBits(Op.getOperand(0), InDemandedBits, Known, TLO,
Depth+1)) Depth+1))
return true; return true;
Known = Known.zext(BitWidth); assert(!Known.hasConflict() && "Bits known to be one AND zero?");
// If the sign bit is known one, the top bits match.
Known = Known.sext(BitWidth);
// If the sign bit is known zero, convert this to a zero extend. // If the sign bit is known zero, convert this to a zero extend.
if (Known.Zero.intersects(InSignBit)) if (Known.isNonNegative())
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ZERO_EXTEND, dl, return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ZERO_EXTEND, dl,
Op.getValueType(), Op.getValueType(),
Op.getOperand(0))); Op.getOperand(0)));
// If the sign bit is known one, the top bits match.
if (Known.One.intersects(InSignBit)) {
Known.One |= NewBits;
assert((Known.Zero & NewBits) == 0);
} else { // Otherwise, top bits aren't known.
assert((Known.One & NewBits) == 0);
assert((Known.Zero & NewBits) == 0);
}
break; break;
} }
case ISD::ANY_EXTEND: { case ISD::ANY_EXTEND: {