[PATCH] D59535: [SelectionDAG] Compute known bits of CopyFromReg

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Hello. I added a constant address case in rL358114 <https://reviews.llvm.org/rL358114>, and a couple of other tests for minsize in rL358128 <https://reviews.llvm.org/rL358128>. I was trying to look into X86 tests, but the addressing modes being so extensive makes it difficult. There will possibly be some RISCV testcases out of D60294 <https://reviews.llvm.org/D60294> too.

One of the problems is that I think, because this was working on demand bits, it was actually converting something from aaaaaaxx + xxxxxxbb -> aaaaaaxx | xxxxxxbb and from there computing aaaaaabb directly (if you understand my meaning, x's are unknowns). If there wasn't the right seperation of bits, this may not have come up. Hence the existing test cases not catching things, but it coming up quite a few times in practice.

Hopefully the new tests are at least enough to show some problem cases. Let me know if not, or if there's any other way I can help.


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https://reviews.llvm.org/D59535