[PATCH] D158673: [SDAG][RISCV] Avoid neg instructions when lowering atomic_load_sub with a constant rhs

[Yingwei Zheng via Phabricator via llvm-commits]

dtcxzyw added a comment.

In D158673#4614846 <https://reviews.llvm.org/D158673#4614846>, @jrtc27 wrote:

> Can we not just teach SelectionDAG to handle ATOMIC_LOAD_SUB=Expand, ATOMIC_LOAD_ADD=Legal?

I think we can let `RISCVTargetLowering::shouldExpandAtomicRMWInIR(atomicrmw sub)` return `Expand` and handle it in `RISCVTargetLowering::emitExpandAtomicRMW`.


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  https://reviews.llvm.org/D158673/new/

https://reviews.llvm.org/D158673