Flushing denormals is a better default behavior for SIMD
engines, since they tend handle denormals slowly (SSE,
Altivec) or not at all (NEON).  Unfortunately, that
behavior is expensive to emulate on IEEE-compliant FPUs,
since you need to check for denormal before and after
every operation.  At this point, the emulator flushes
denormals and C code does not.