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Fix INT_MIN gotcha pointed out by Eli Friedman.

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llvm-svn: 128028
This commit is contained in:
Nick Lewycky 2011-03-21 21:40:32 +00:00
parent bf35de8849
commit e8f6eb49ee
1 changed files with 4 additions and 3 deletions
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7
lib/Analysis/ValueTracking.cpp
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@ -725,9 +725,10 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) {
isPowerOfTwo(SI->getFalseValue(), TD, Depth);
// 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.
if (match(V, m_Shr(m_Value(), m_Value())) ||
match(V, m_IDiv(m_Value(), m_Value()))) {
// is a power of two only if the first operand is a power of two and not
// copying a sign bit (sdiv int_min, 2).
if (match(V, m_LShr(m_Value(), m_Value())) ||
match(V, m_UDiv(m_Value(), m_Value()))) {
BinaryOperator *BO = cast<BinaryOperator>(V);
if (BO->isExact())
return isPowerOfTwo(BO->getOperand(0), TD, Depth);