Is there a compiler hint for GCC to force branch prediction to always go a certain way?

GCC supports the function __builtin_expect(long exp, long c) to provide this kind of feature. You can check the documentation here.

Where exp is the condition used and c is the expected value. For example in you case you would want

if (__builtin_expect(normal, 1))

Because of the awkward syntax this is usually used by defining two custom macros like

#define likely(x)    __builtin_expect (!!(x), 1)
#define unlikely(x)  __builtin_expect (!!(x), 0)

just to ease the task.

Mind that:

1. this is non standard
2. a compiler/cpu branch predictor are likely more skilled than you in deciding such things so this could be a premature micro-optimization