[PATCH] D155328: [RISCV] Add a DAG combine for (czero_eq X, (xor Y, 1)) -> (czero_ne X, Y) if Y is 0 or 1.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

In D155328#4502274 <https://reviews.llvm.org/D155328#4502274>, @mgudim wrote:

> LGTM, but it seems weird to me that we have to re-implement such basic optimisations instead of generic code doing this.  @craig.topper @asb I know I asked this is the call, but I still don't understand why we emit target-specific node for SELECT so early?

There isn’t a generic combine for this on select after type legalization. It depends on getBooleanContents to know the value for true. So I think it only exists for i1.


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https://reviews.llvm.org/D155328