[PATCH] D135078: [AArch64][GlobalISel] Fold away lowered vector sign-extend of vector compares

Mon Oct 3 14:29:45 PDT 2022

arsenm added a comment.

In D135078#3830895 <https://reviews.llvm.org/D135078#3830895>, @aemerson wrote:

> In D135078#3830892 <https://reviews.llvm.org/D135078#3830892>, @arsenm wrote:
>
>> This should have been caught and combined into g_sext_inreg, which should have folded out based on computeNumSignBits
>
> The only place we have an opportunity to catch the extend before it gets legalized into shifts is in the artifact combiner, and this is just a code quality optimization so it shouldn't go there.

The shifts themselves combine into g_sext_inreg

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https://reviews.llvm.org/D135078