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Hi Justin, This is a big weakness of the current SelectionDAG infrastructure. There's not a really clean way to do this. The legalizer assumes that if a type is "legal" at all, the target can do at least basic arithmetic on that type. Theoretically, your approach of setting the operations to "TargetLowering::Promote" for i8 should work. I think it would be reasonable to

Is there a way to define a register class that is storage-only? I want to have an i8 register class that I can use for loads/stores/converts, but that does not support arithmetic. It seems addOperationAction(ISD::ADD, MVT::i8, Promote) and SetPromotedToType(ISD::ADD, MVT::i8, MVT::i16) are not sufficient, as the legalizer just looks at whether or not the underlying type is legal (which it is).

...ev at cs.uiuc.edu http://llvm.cs.uiuc.edu > > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > -- Thanks, Justin Holewinski -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130808/1c9006f0/attachment.html>