[PATCH] D143880: [LoongArch] Emit bytepick for picking from concatenation of two values

Mon Feb 13 04:53:27 PST 2023

xry111 added a comment.

In D143880#4122602 <https://reviews.llvm.org/D143880#4122602>, @xen0n wrote:

> In D143880#4121913 <https://reviews.llvm.org/D143880#4121913>, @xen0n wrote:
>
>> @xry111: BTW your GCC implementation of this pattern looks for *arithmetic* right shifts; do you mean logical instead? Because obviously the higher bits would be full of ones after shifting if `rj` happen to have its MSB set. The sign extension shall happen *after* the pick.
>
> My bad, I'm not familiar with GCC RTL patterns so I've mistakenly thought "`lshiftrt` could be some 'left' shift, so `ashift` must be an arithmetic right shift". Actually your pattern is correct as you have perfect test coverage. Please ignore my comment...

Yes, the naming in GCC confused me as well :).

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https://reviews.llvm.org/D143880