diff options
Diffstat (limited to 'lib/Analysis')
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 46 |
1 files changed, 30 insertions, 16 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 84a6346..4591af8 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -855,22 +855,36 @@ bool llvm::isKnownToBeAPowerOfTwo(Value *V, bool OrZero, unsigned Depth) { return false; } - if (match(V, m_Add(m_Value(X), m_Value(Y)))) - if (OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V)) - if (OrZero || VOBO->hasNoUnsignedWrap() || VOBO->hasNoSignedWrap()) { - // Adding a power of two to the same power of two is a power of two or - // zero. - if (BinaryOperator *XBO = dyn_cast<BinaryOperator>(X)) - if (XBO->getOpcode() == Instruction::And) - if (XBO->getOperand(0) == Y || XBO->getOperand(1) == Y) - if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth)) - return true; - if (BinaryOperator *YBO = dyn_cast<BinaryOperator>(Y)) - if (YBO->getOpcode() == Instruction::And) - if (YBO->getOperand(0) == X || YBO->getOperand(1) == X) - if (isKnownToBeAPowerOfTwo(X, OrZero, Depth)) - return true; - } + // Adding a power-of-two or zero to the same power-of-two or zero yields + // either the original power-of-two, a larger power-of-two or zero. + if (match(V, m_Add(m_Value(X), m_Value(Y)))) { + OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V); + if (OrZero || VOBO->hasNoUnsignedWrap() || VOBO->hasNoSignedWrap()) { + if (match(X, m_And(m_Specific(Y), m_Value())) || + match(X, m_And(m_Value(), m_Specific(Y)))) + if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth)) + return true; + if (match(Y, m_And(m_Specific(X), m_Value())) || + match(Y, m_And(m_Value(), m_Specific(X)))) + if (isKnownToBeAPowerOfTwo(X, OrZero, Depth)) + return true; + + unsigned BitWidth = V->getType()->getScalarSizeInBits(); + APInt LHSZeroBits(BitWidth, 0), LHSOneBits(BitWidth, 0); + ComputeMaskedBits(X, LHSZeroBits, LHSOneBits, 0, Depth); + + APInt RHSZeroBits(BitWidth, 0), RHSOneBits(BitWidth, 0); + ComputeMaskedBits(Y, RHSZeroBits, RHSOneBits, 0, Depth); + // If i8 V is a power of two or zero: + // ZeroBits: 1 1 1 0 1 1 1 1 + // ~ZeroBits: 0 0 0 1 0 0 0 0 + if ((~(LHSZeroBits & RHSZeroBits)).isPowerOf2()) + // If OrZero isn't set, we cannot give back a zero result. + // Make sure either the LHS or RHS has a bit set. + if (OrZero || RHSOneBits.getBoolValue() || LHSOneBits.getBoolValue()) + return true; + } + } // An exact divide or right shift can only shift off zero bits, so the result // is a power of two only if the first operand is a power of two and not |