We're using the Lite version of the MicroChip PIC compiler so maybe that's the reason, but this simple one-bit shift is generating a loop where none is necessary. Since the shift count is 1 (a constant), I would expect the compiler to create no loop—an elementary optimization.
Is there a compiler optimization switch that would alleviate the loop? Here is the code for the shift:
long foo; // a 32-bit value // Shift foo one bit. // A one-iteration loop is created! foo >>= 1;
And here is the compiler-generated code. As you can see, the shift is wrapped with a one-iteration loop.
07F6 3001 MOVLW 0x1 07F7 00F2 MOVWF 0x72 07F8 37F6 ASRF 0x76, F 07F9 0CF5 RRF 0x75, F 07FA 0CF4 RRF 0x74, F 07FB 0CF3 RRF 0x73, F 07FC 0BF2 DECFSZ 0x72, F
Compiler Version: HI-TECH C Compiler for PIC10/12/16 MCUs (Lite Mode) V9.81