On Wednesday 19 March 2003 03:21, David Walser wrote: > Could the application itself just have runtime detection of CPU > features, so you can compile SSE/MMX support in the one package, but it > won't try to use it on CPUs that don't support it? I think mplayer does > this, and didn't use to.
This would be fine if every application did this, but many don't--and won't. To make runtime-selected SSE/MMX work as efficiently as compile-time is a lot of work (you obviously can't switch on a runtime flag in the middle of a tight loop). There are a variety of ways to do this, but none are as #ifdef'ing around the code, so that's what most developers do. Also, there are cases where the there's no explicit code in the application to take advantage of SSE/MMX, but the optimizer can find some use for it anyway. There's obviously no way to switch around this at runtime.
