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Add an APInt version of ShrinkDemandedConstant.
Patch by Zhou Sheng. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35063 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1004,6 +1004,30 @@ static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
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return true;
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}
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/// ShrinkDemandedConstant - Check to see if the specified operand of the
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/// specified instruction is a constant integer. If so, check to see if there
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/// are any bits set in the constant that are not demanded. If so, shrink the
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/// constant and return true.
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static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
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APInt Demanded) {
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assert(I && "No instruction?");
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assert(OpNo < I->getNumOperands() && "Operand index too large");
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// If the operand is not a constant integer, nothing to do.
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ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
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if (!OpC) return false;
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// If there are no bits set that aren't demanded, nothing to do.
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Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
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if ((~Demanded & OpC->getValue()) == 0)
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return false;
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// This instruction is producing bits that are not demanded. Shrink the RHS.
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Demanded &= OpC->getValue();
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I->setOperand(OpNo, ConstantInt::get(Demanded));
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return true;
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}
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// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
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// set of known zero and one bits, compute the maximum and minimum values that
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// could have the specified known zero and known one bits, returning them in
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