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bcf124c07d
This commit addresses the following shortcomings of our current, simple and elegant memset function: - REP STOSB/STOSQ has considerable startup overhead, it's impractical to use for smaller sizes. - Up until very recently, AMD CPUs didn't have support for "Enhanced REP MOVSB/STOSB", so it performed pretty poorly on them. With this commit applied, I could measure a ~5% decrease in `test-js`'s runtime when I used qemu's TCG backend. The implementation is based on the following article from Microsoft: https://msrc-blog.microsoft.com/2021/01/11/building-faster-amd64-memset-routines Two versions of the routine are implemented: one that uses the ERMS extension mentioned above, and one that performs plain SSE stores. The version appropriate for the CPU is selected at load time using an IFUNC. |
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