TR::Node *
OMR::Simplifier::unaryCancelOutWithChild(TR::Node * node, TR::Node * firstChild, TR::TreeTop *anchorTree, TR::ILOpCodes opcode, bool anchorChildren)
{
if (!isLegalToUnaryCancel(node, firstChild, opcode))
return NULL;
if (firstChild->getOpCodeValue() == opcode &&
(node->getType().isAggregate() || firstChild->getType().isAggregate()) &&
(node->getSize() > firstChild->getSize() || node->getSize() != firstChild->getFirstChild()->getSize()))
{
// ensure a truncation side-effect of a conversion is not lost
// o2a size=3
// a2o size=3 // conversion truncates in addition to type cast so cannot be removed
// loadaddr size=4
// This restriction could be loosened to only disallow intermediate truncations (see BCD case above) but then would require a node
// op that would just correct for size (e.g. addrSizeMod size=3 to replace the o2a/a2o pair)
//
// Do allow cases when all three sizes are the same and when the middle node widens but the top and bottom node have the same size, e.g.
//
// i2o size=3
// o2i size=4
// oload size=3
//
// Also allow the special case where the grandchild is not really truncated as the 'truncated' bytes are known to be zero
// (i.e. there really isn't an intermediate truncation of 4->3 even though it appears that way from looking at the sizes alone)
// o2i
// i2o size=3
// iushr
// x
// iconst 8
bool disallow = true;
TR::Node *grandChild = firstChild->getFirstChild();
size_t nodeSize = node->getSize();
if (node->getType().isIntegral() &&
nodeSize == grandChild->getSize() &&
nodeSize > firstChild->getSize())
{
size_t truncatedBits = (nodeSize - firstChild->getSize()) * 8;
if (grandChild->getOpCode().isRightShift() && grandChild->getOpCode().isShiftLogical() &&
grandChild->getSecondChild()->getOpCode().isLoadConst() &&
(grandChild->getSecondChild()->get64bitIntegralValue() == truncatedBits))
{
disallow = false;
if (trace())
traceMsg(comp(),"do allow unaryCancel of node %s (%p) and firstChild %s (%p) as grandChild %s (%p) zeros the %d truncated bytes\n",
node->getOpCode().getName(),node,firstChild->getOpCode().getName(),firstChild,
grandChild->getOpCode().getName(),grandChild,truncatedBits/8);
}
}
if (disallow)
{
if (trace())
traceMsg(comp(),"disallow unaryCancel of node %s (%p) and firstChild %s (%p) due to unequal sizes (nodeSize %d, firstChildSize %d, firstChild->childSize %d)\n",
node->getOpCode().getName(),node,firstChild->getOpCode().getName(),firstChild,
node->getSize(),firstChild->getSize(),firstChild->getFirstChild()->getSize());
return NULL;
}
}
if (firstChild->getOpCodeValue() == opcode &&
performTransformation(comp(), "%sRemoving node [" POINTER_PRINTF_FORMAT "] %s and its child [" POINTER_PRINTF_FORMAT "] %s\n",
optDetailString(), node, node->getOpCode().getName(), firstChild, firstChild->getOpCode().getName()))
{
TR::Node *grandChild = firstChild->getFirstChild();
grandChild->incReferenceCount();
bool anchorChildrenNeeded = anchorChildren &&
(node->getNumChildren() > 1 ||
firstChild->getNumChildren() > 1 ||
node->getOpCode().hasSymbolReference() ||
firstChild->getOpCode().hasSymbolReference());
prepareToStopUsingNode(node, anchorTree, anchorChildrenNeeded);
node->recursivelyDecReferenceCount();
node->setVisitCount(0);
return grandChild;
}
return NULL;
}
