On Mon, 13 Dec 2021 at 21:06:55 -0600, Steven Robbins wrote:
Is the choice of baseline a Debian-specific configuration of GCC?
Yes, it is a Debian-specific choice. For example, Ubuntu moved from i586
to i686 before we did. I believe Debian and Ubuntu are *currently* in sync
on this, but there is no particular reason why we have to be.
Technically our baseline is i686, minus one "long NOP" instruction that
wasn't supported by a generation of AMD Geode CPUs that is otherwise i686.
It's a tradeoff with no single correct answer: increasing the baseline
makes the OS work better (faster and/or fewer bugs) on CPUs newer than
the baseline, at the cost of making it completely non-functional on CPUs
older than the baseline.
Or might
another OS vendor configure differently such that "gcc" running on an i386 class
machine actually targets something newer than i686?
Yes, they might. I'm sure several vendors with a focus on relatively
modern mainstream consumer or server hardware are configuring their i386
gcc to target machines with SSE and SSE2, both for better performance
on newer CPUs and so that they don't have to deal with the historical
oddities of the i387 FPU. The Intel-sponsored Clear Linux is notably enthusiastic about raising its baseline beyond what most vendors would consider.
Conversely, some vendors with more focus on embedded systems (OpenWRT?) probably still target i586 or i486, like older Debian did.
smcv
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