zhijian lin 41647412c6 [PowerPC] Fix an LowerADDSUBO_CARRY error when converting carry bit for usubo_carry (#137809) ...

In PowerPC, if a borrow occurs during a subtraction, the carry bit is
zero (unset). The carry bit is set if no borrow occurs.

For ISD::USUBO_CARRY, the nodes produce two results: the normal result
of the addition or subtraction, and a boolean value that is 1 if and
only if there is an outgoing carry or borrow.

Therefore, we need to convert a 1 (which indicates a borrow in
ISD::USUBO_CARRY) to 0 to match PowerPC's definition of borrow.
Similarly, we need to convert a 0 (no borrow in ISD::USUBO_CARRY) to 1
for PowerPC.

To perform this conversion, we use XOR 1 instead of XOR
DAG.getAllOnesConstant(DL, CarryOp.getValueType()).

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2025-04-30 10:39:09 -04:00

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