[DAG] PromoteIntRes_ADDSUBSHLSAT - use promoted ISD::USUBSAT directly
As discussed on D96413, as long as the promoted bits of the args are zero we can use the basic ISD::USUBSAT pattern directly, without the shifting like we do for other ops.
I think something similar should be possible for ISD::UADDSAT as well, which I'll look at later.
Also, create a ISD::USUBSAT node directly - this will be expanded back by the legalizer later on if necessary.
Differential Revision: https://reviews.llvm.org/D96622
GitOrigin-RevId: 60ba5397dfbf28ffe6ec670f0cb29cf892591106
6 files changed
