I just tried this with IAR for Cortex-M3. I didn't check thoroughly, but so far it looks like right-aligned bitfields of eight bits or less generate an LDRB (8-

I just tried this with IAR for Cortex-M3. I didn't check thoroughly, but so far it looks like right-aligned bitfields of eight bits or less generate an LDRB (8-bit). All other bitfields generate an LDR (32-bit), even if they lie entirely within a byte. I see the makings of a fun trick to play on a colleague. I don't see anything I'd be too inclined to use in production code.