__builtin_expect vs. PGO

[Ian Lance Taylor]

Scott Meyers <NeverRead@aristeia.com> writes:

> What has more weight during codegen in a compilation with
> -fprofile-use when the code uses __builtin_expect to favor one branch
> while the PGO data says the other branch is more likely?

I believe the probabilities will be combined in that case.  The
weighting of __builtin_expect is such that it will most likely be the
predicted case, unless the profiling data says that the unexpected path
is always taken.

Ian