[PATCH] D114357: [CodeGen][AArch64] Ensure isSExtCheaperThanZExt returns true for negative constants

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo added a comment.

In D114357#3250516 <https://reviews.llvm.org/D114357#3250516>, @david-arm wrote:

> Hi @mstorsjo, thanks for the info. I'll revert the patch again for now. It's strange because ANY_EXTEND should really mean "any", i.e. you don't care if it's sign-extend or zero-extend! I suspect there is a bug in codegen somewhere that either relies upon ANY_EXTEND actually being ZERO_EXTEND, or relies upon ANY_EXTEND being consistently the same. I'm worried because the `isSExtCheaperThanZExt` interface definitely allows for the possibility of sometimes choosing one over the other depending upon the types.

Thanks, and that does indeed seem worrying.

For the sake of finding other possible similar related cases, with the same instructions, but with `make -j$(nproc) fate` it runs all tests - which currently triggered 24 failed tests (of which I believe there's maybe a 3-6 actual individual breakages), if you want to rerun more tests when you think you've pinpointed the root cause.


Repository:
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  https://reviews.llvm.org/D114357/new/

https://reviews.llvm.org/D114357