Re: Add RISC-V Zbb popcount optimization - Mailing list pgsql-hackers

From Andres Freund
Subject Re: Add RISC-V Zbb popcount optimization
Date
Msg-id fnrwgvtglac54qgzkjquppcuxj4kjhxcroiemgnlsdick6cehy@l7bnbja7mn4b
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In response to Add RISC-V Zbb popcount optimization  ("Greg Burd" <greg@burd.me>)
Responses Re: Add RISC-V Zbb popcount optimization
List pgsql-hackers
Hi,

On 2026-03-21 12:54:10 -0400, Greg Burd wrote:
> Attached is a small patch that enables hardware popcount on RISC-V when
> available and also sets the arch flag to 'rv64gc_zbb' flag when appropriate.

Maybe I'm missing something: How is the latter approach safe without a runtime
check?  Just because it compiled on the build machine with -march=rv64gc_zbb
added doesn't mean it runs on either the build machine or any other machine?

If this worked, the compiler could just always specify -march=rv64gc_zbb, no?

Greetings,

Andres Freund



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