[all-commits] [llvm/llvm-project] 416474: [PowerPC] Fix an LowerADDSUBO_CARRY error when con...

[zhijian lin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 41647412c6a4091080fd47b0f554adc5c54b4b54
      https://github.com/llvm/llvm-project/commit/41647412c6a4091080fd47b0f554adc5c54b4b54
  Author: zhijian lin <zhijian at ca.ibm.com>
  Date:   2025-04-30 (Wed, 30 Apr 2025)

  Changed paths:
    M llvm/lib/Target/PowerPC/PPCISelLowering.cpp
    A llvm/test/CodeGen/PowerPC/usubo_carry.ll

  Log Message:
  -----------
  [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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