8.1.8 Bit-shifting Operations.

Bit shifting is one of the most frequently used operation in embedded programming. SDCC tries to implement bit-shift operations in the most efficient way possible, e.g.:

unsigned char i; 
...  
i >>= 4;  
...

generates the following code:

mov  a,_i  
swap a  
anl  a,#0x0f  
mov  _i,a

In general SDCC will never setup a loop if the shift count is known. Another example:

unsigned int i;  
...  
i >>= 9;  
...

will generate:

mov  a,(_i + 1)  
mov  (_i + 1),#0x00  
clr  c  
rrc  a  
mov  _i,a