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Add fix for tryToReplaceShiftLandWithRotateInstruction #4427

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Oct 10, 2019
Merged

Add fix for tryToReplaceShiftLandWithRotateInstruction #4427

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8 changes: 7 additions & 1 deletion compiler/z/codegen/BinaryEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1816,7 +1816,6 @@ OMR::Z::TreeEvaluator::tryToReplaceShiftLandWithRotateInstruction(TR::Node * nod
// RISBG instructions perform unsigned rotation, so if we are selecting the sign bit via the logical AND we cannot
// perform a signed shift because we must preserve the sign bit. In general we cannot handle this case because we are
// not certain our input will be non-negative, hence we must conservatively disallow the optimization in such a case.

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Formatting fix

if (longConstValue >= 0x8000000000000000LL && shiftAmount != 0 && isSignedShift)
{
return NULL;
Expand All @@ -1826,6 +1825,13 @@ OMR::Z::TreeEvaluator::tryToReplaceShiftLandWithRotateInstruction(TR::Node * nod
{
return NULL;
}
// If the node entered is a common node, then there is no guarantee that the child of the common node will still be alive.
// And when we try to access the value in that node, we might receive values from a node that might've been killed already.
// Thus, the optimization will not work.
if (node->getRegister() != NULL)
{
return NULL;
}
int32_t tZeros = trailingZeroes(longConstValue);
int32_t lZeros = leadingZeroes(longConstValue);
int32_t tOnes = trailingZeroes(~longConstValue);
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