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[SelectionDAG] Early out from computeKnownBits when we know we will have no common bits.

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Avoid extra (recursive) calls to computeKnownBits if we already know that there are no common known bits.

llvm-svn: 290490
This commit is contained in:
Simon Pilgrim 2016-12-24 12:59:35 +00:00
parent 4369adcbc1
commit 3d00c1e5ad
1 changed files with 26 additions and 8 deletions
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34
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -2087,7 +2087,10 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
if (M < 0) {
// For UNDEF elements, we don't know anything about the common state of
// the shuffle result.
KnownZero = KnownOne = APInt(BitWidth, 0);
KnownOne.clearAllBits();
KnownZero.clearAllBits();
DemandedLHS.clearAllBits();
DemandedRHS.clearAllBits();
break;
}
@ -2103,6 +2106,9 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
}
// If we don't know any bits, early out.
if (!KnownOne && !KnownZero)
break;
if (!!DemandedRHS) {
SDValue RHS = Op.getOperand(1);
computeKnownBits(RHS, KnownZero2, KnownOne2, DemandedRHS, Depth + 1);
@ -2126,6 +2132,9 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
}
// If we don't know any bits, early out.
if (!KnownOne && !KnownZero)
break;
}
break;
}
@ -2207,6 +2216,9 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
unsigned Offset = (i % SubScale) * BitWidth;
KnownOne &= KnownOne2.lshr(Offset).trunc(BitWidth);
KnownZero &= KnownZero2.lshr(Offset).trunc(BitWidth);
// If we don't know any bits, early out.
if (!KnownOne && !KnownZero)
break;
}
}
break;
@ -2290,6 +2302,9 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
}
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);
// Only known if known in both the LHS and RHS.
@ -2298,6 +2313,9 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
break;
case ISD::SELECT_CC:
computeKnownBits(Op.getOperand(3), KnownZero, KnownOne, Depth+1);
// If we don't know any bits, early out.
if (!KnownOne && !KnownZero)
break;
computeKnownBits(Op.getOperand(2), KnownZero2, KnownOne2, Depth+1);
// Only known if known in both the LHS and RHS.
@ -2691,15 +2709,15 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
case ISD::SMAX:
case ISD::UMIN:
case ISD::UMAX: {
APInt Op0Zero, Op0One;
APInt Op1Zero, Op1One;
computeKnownBits(Op.getOperand(0), Op0Zero, Op0One, DemandedElts,
computeKnownBits(Op.getOperand(0), KnownZero, KnownOne, DemandedElts,
Depth + 1);
computeKnownBits(Op.getOperand(1), Op1Zero, Op1One, DemandedElts,
// If we don't know any bits, early out.
if (!KnownOne && !KnownZero)
break;
computeKnownBits(Op.getOperand(1), KnownZero2, KnownOne2, DemandedElts,
Depth + 1);
KnownZero = Op0Zero & Op1Zero;
KnownOne = Op0One & Op1One;
KnownZero &= KnownZero2;
KnownOne &= KnownOne2;
break;
}
case ISD::FrameIndex: