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Check RHS simplification before LHS simplification to avoid infinitely looping
on PowerPC/small-arguments.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26389 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -201,7 +201,23 @@ bool TargetLowering::SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask,
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KnownZero = ~KnownOne & DemandedMask;
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return false; // Don't fall through, will infinitely loop.
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case ISD::AND:
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// If either the LHS or the RHS are Zero, the result is zero.
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// If the RHS is a constant, check to see if the LHS would be zero without
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// using the bits from the RHS. Below, we use knowledge about the RHS to
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// simplify the LHS, here we're using information from the LHS to simplify
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// the RHS.
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if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
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uint64_t LHSZero, LHSOne;
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ComputeMaskedBits(Op.getOperand(0), DemandedMask,
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LHSZero, LHSOne, Depth+1);
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// If the LHS already has zeros where RHSC does, this and is dead.
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if ((LHSZero & DemandedMask) == (~RHSC->getValue() & DemandedMask))
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return TLO.CombineTo(Op, Op.getOperand(0));
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// If any of the set bits in the RHS are known zero on the LHS, shrink
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// the constant.
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if (TLO.ShrinkDemandedConstant(Op, ~LHSZero & DemandedMask))
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return true;
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}
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if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero,
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KnownOne, TLO, Depth+1))
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return true;
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@ -224,23 +240,6 @@ bool TargetLowering::SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask,
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if (TLO.ShrinkDemandedConstant(Op, DemandedMask & ~KnownZero2))
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return true;
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// If the RHS is a constant, check to see if the LHS would be zero without
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// using the bits from the RHS. Above, we used knowledge about the RHS to
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// simplify the LHS, here we're using information from the LHS to simplify
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// the RHS.
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if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
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uint64_t LHSZero, LHSOne;
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ComputeMaskedBits(Op.getOperand(0), DemandedMask,
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LHSZero, LHSOne, Depth+1);
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// If the LHS already has zeros where RHSC does, this and is dead.
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if ((LHSZero & DemandedMask) == (~RHSC->getValue() & DemandedMask))
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return TLO.CombineTo(Op, Op.getOperand(0));
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// If any of the set bits in the RHS are known zero on the LHS, shrink
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// the constant.
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if (TLO.ShrinkDemandedConstant(Op, ~LHSZero & DemandedMask))
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return true;
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}
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// Output known-1 bits are only known if set in both the LHS & RHS.
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KnownOne &= KnownOne2;
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// Output known-0 are known to be clear if zero in either the LHS | RHS.
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