Re: __atomic_test_and_set() and mips o32 - help wanted

[David Holland <dholland-tech%netbsd.org@localhost>]

On Mon, Nov 17, 2025 at 02:51:56PM +1100, Simon Burge wrote:
 > > i'm not sure what the right thing to do here is.  it's not clear
 > > to me that the actual old 32-bit hardware can do this at all, but
 > > there are now explicit calls to this builtin.  GCC configury tries
 > > to find and notice it's missing, but libstdc++ still has a couple
 > > of calls to it directly in it's "test_and_set()".
 > >
 > >
 > > anyone have a good idea?
 > 
 > MIPS1 has no ll/sc or any other atomic primatives.  SMP R3000
 > boxes (eg DECsystem 54x0) used external hardware for this.
 > 
 > Seems like RAS (see rasctl(2)) might be the only (simple?)
 > option for MIPS1/o32 ?

mips1 and o32 aren't the same thing. All 32-bit MIPS hardware, which
includes 32-bit builds on otherwise 64-bit macines, will necessarily
be using o32.

Anyway, despite what the rest of the thread seems to think, surely
it's not necessary to hack the compiler, just to provide a mips1
implementation of the missing symbol on mips1 ports? Which can then be
an ll/sc sequence to be emulated, or a RAS, or whatever else...

-- 
David A. Holland
dholland%netbsd.org@localhost