On 4/28/23 15:42, Hans Boehm wrote:
The concern with making the new behavior non-default is of course that
the generated code will eventually end up on an A.7-capable platform.
Yea, certainly a significant concern in general, though probably not for
Ventana. I expect we'll have folks rebuilding as they go from V1 to V2
due to the ventanacondops -> condops change.
An A.6-classic option for compiling code that will never run on a newer
machine seems OK. But I'm not sure that seq_cst stores are dynamically
frequent enough in C++ code for this to be worth the trouble.
Unlike loads, they are also costly on x86, programmers may also have
been somewhat trained to avoid them where possible. (And probably where
not possible, too :-( )
I was more worried about the kernel, perhaps because I'm less familiar
with it these days than ever. WRT C++, I can ping Jon@RedHat, he's got
a great sense what's in the standard library obviously, but also a
reasonable sense of what folks are doing in the wild.
Jeff
