Should the build system use ar rcs instead of ranlib + ar rc?

[Andreas Schwab]

Andrew Pinski <pinskia@gmail.com> writes:

> On Fri, Jul 15, 2016 at 6:46 PM, Patrick Palka <patrick@parcs.ath.cx> wrote:
>> The build step that invokes "ranlib libbackend.a" (which immediately
>> follows the invocation of "ar rc libbackend.a ...") takes over 7 seconds
>> on my machine and causes the entire 450MB archive to be rewritten.  By
>> instead making the build system use ar rcs -- so that the archive and
>> its index are built at once -- the time it takes for the compiler to get
>> rebuilt gets reduced by 25%, from 27s to 20s (in a --disable-bootstrap
>> tree after touching a random source file).  This is a pretty significant
>> reduction in compile time and disk io.
>>
>> Is this a good idea?
>
> Yes and no.  Do we know if all ar support rcs now?

It is easy to find out: run a configure check.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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