RFR: 8265768 [aarch64] Use glibc libm impl for dlog, dlog10, dexp iff 2.29 or greater on AArch64.

[gregcawthorne]

On Tue, 27 Apr 2021 09:57:21 GMT, Andrew Haley <aph at openjdk.org> wrote:

> One other thing: I can't find any reference to monotonicity in the libc 2.29 documentation. In fact, I can't find any references at all to the glibc 2.29 changes in this area. Please provide some pointers, thanks.

Hi Aph.

I have added a link:
https://sourceware.org/legacy-ml/libc-announce/2019/msg00000.html

As a comment in os_linux_aarch64.cpp, in the patch.

This mentions the improvements for exp and log in glib version 2.29 (log10 calls down to log I believe).

My understanding was also driven by speaking to Szabolcs Nagy inside arm, who maintains our (AOR) Arm Optimised Routines library. It is from this library from which these improvements have been included into glibc.

We have talked about the possibility of including AOR in OpenJDK. But that seems to be more of a legality question at this point in time, as I am informed the Free Software Foundation currently holds the copyright to AOR.

Thanks,
Greg.

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PR: https://git.openjdk.java.net/jdk/pull/3510