Re: [PATCH] audo-detect and use -moutline-atomics compilation flag for aarch64 - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [PATCH] audo-detect and use -moutline-atomics compilation flag for aarch64
Date
Msg-id 1713568.1599516054@sss.pgh.pa.us
Whole thread Raw
In response to [PATCH] audo-detect and use -moutline-atomics compilation flag for aarch64  ("Zidenberg, Tsahi" <tsahee@amazon.com>)
Responses Re: [PATCH] audo-detect and use -moutline-atomics compilation flag for aarch64  ("Zidenberg, Tsahi" <tsahee@amazon.com>)
List pgsql-hackers
"Zidenberg, Tsahi" <tsahee@amazon.com> writes:
> Outline-atomics is a gcc compilation flag that adds runtime detection of weather or not the cpu supports atomic
instructions.CPUs that don't support atomic instructions will use the old load-exclusive/store-exclusive instructions.
Ifa different compilation flag defined an architecture that unconditionally supports atomic instructions (e.g.
-march=armv8.2),the outline-atomic flag will have no effect. 

I wonder what version of gcc you intend this for.  AFAICS, older
gcc versions lack this flag at all, while newer ones have it on
by default.  Docs I can find on the net suggest that it would only
help to supply the flag when using gcc 10.0.x.  Is there a sufficient
population of production systems using such gcc releases to make it
worth expending configure cycles on?  (That's sort of a trick question,
because the GCC docs make it look like 10.0.x was never considered
to be production ready.)

            regards, tom lane



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