[llvm-dev] how to implement an instruction that does not exist in instruction set

[林政宗 via llvm-dev]

Hi, there


I am writing an new backend. And I don't have vsge(vector set when larger than or equal to) instruction in the instruction set.
How could I implement the instruction? I have vslt(vector set when less than) instruction, vseq(vector set when equal to), vneg(vector negate), vand(vector and), vor(vector or) and vxor(vector xor) in the instruction set.
Should I consider the situation when one of the operand of vsge is nan(not a number)?
Where should I implement the vsge operation? Should it be implemented in the SelectionDAG lowering step or the pseudo instruction expansion step?


Thanks!




Best regards,
Jerry 
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