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In function ComputeMaskedBits():

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1. Replace getSignedMinValue() with getSignBit() for better code readability.
  2. Replace APIntOps::shl() with operator<<= for convenience.
  3. Make APInt construction more effective.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35060 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-12 05:44:52 +00:00
parent 8db6a445e6
commit 430f626937
1 changed files with 6 additions and 6 deletions
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12
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -695,7 +695,7 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
APInt InSignBit(APInt::getSignedMinValue(SrcTy->getBitWidth()));
APInt InSignBit(APInt::getSignBit(SrcTy->getBitWidth()));
InSignBit.zextOrTrunc(BitWidth);
if ((KnownZero & InSignBit) != 0) { // Input sign bit known zero
KnownZero |= NewBits;
@ -716,8 +716,8 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
Mask = APIntOps::lshr(Mask, ShiftAmt);
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero = APIntOps::shl(KnownZero, ShiftAmt);
KnownOne = APIntOps::shl(KnownOne, ShiftAmt);
KnownZero <<= ShiftAmt;
KnownOne <<= ShiftAmt;
KnownZero |= APInt(BitWidth, 1ULL).shl(ShiftAmt)-1; // low bits known zero.
return;
}
@ -730,7 +730,7 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth-ShiftAmt));
// Unsigned shift right.
Mask = APIntOps::shl(Mask, ShiftAmt);
Mask <<= ShiftAmt;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
@ -747,14 +747,14 @@ static void ComputeMaskedBits(Value *V, APInt Mask, APInt& KnownZero,
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth-ShiftAmt));
// Signed shift right.
Mask = APIntOps::shl(Mask, ShiftAmt);
Mask <<= ShiftAmt;
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero,KnownOne,Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
// Handle the sign bits and adjust to where it is now in the mask.
APInt SignBit = APInt::getSignedMinValue(BitWidth).lshr(ShiftAmt);
APInt SignBit(APInt::getSignBit(BitWidth).lshr(ShiftAmt));
if ((KnownZero & SignBit) != 0) { // New bits are known zero.
KnownZero |= HighBits;