In compiler.h we define the likely(), unlikely() macros which wrap
GCC's __builtin_expect(). But we only use them in a handful of places.
It seems to me that an obvious place to possibly use these would be
for GL error testing. For example, in glDrawArrays():
if (unlikely(count <= 0)) {
_mesa_error();
}
Plus, in some of the glBegin/End per-vertex calls such as
glVertexAttrib3fARB() where we error test the index parameter.
I guess the key question is how much might we gain from this. I don't
really have a good feel for the value at this level. In a tight inner
loop, sure, but the GL error checking is pretty high-level code.
I haven't found much on the web about performance gains from
__builtin_expect(). Anyone?
-Brian
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