On 07/06/2021 01.39, Rasmus Villemoes wrote:

memory". Replacing with a call to an extern function marked pure does
indeed cause gcc to cache the value of y*z, so in theory this should be
possible, if one could convince gcc to "trust me, this really is a pure
function".

Don't know why I didn't think to check before sending, but FWIW clang
doesn't need convincing, it already takes the __pure at face value and
caches y*z.

Rasmus