[PATCH] D149946: [LoongArch] Define `ual` feature and override `allowsMisalignedMemoryAccesses`

[WÁNG Xuěruì via Phabricator via cfe-commits]

xen0n accepted this revision.
xen0n added a comment.
This revision is now accepted and ready to land.

I've thought about this a bit harder; it now seems better longer-term to enable unaligned accesses by default (making the UAL-less models the special case).

But most importantly, there's new information suggesting that UAL support is to become ubiquitous in the future. A sample `/proc/cpuinfo` output on a Loongson 2K2000 (LA364 uarch) recently is circulated in various user groups (unfortunately there doesn't seem to be a public link), that clearly shows LA364 has UAL. So this very likely means all future Loongson-2 series will feature UAL, and that the non-UAL case is to gradually become less relevant.

Also, in some cases (distro packaging, mesa llvmpipe, etc.) it may not be as easy to specify `march` flags, but we may want to assume a more popular model nevertheless. Again the UAL-less models should be seen as special cases and get adapted individually later.

With the reasoning becoming clear, the LoongArch target part of the change LGTM; thanks for taking care of this!


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