GCC 4.1.2 Issue. New toolchain soon?

Another problem I found - which might be in gcc itself, so might be fixed in later versions...

If I read a 'volatile unsigned char' value, the compiler follows the 'ldbu' instruction with one that masks the value with 0xff.

(It sometimes does it for non-volatiles as well.)

My suspicion is that 'volatile' forces a separate load of the value into a register, then the value from the register is used for the variable reference. Between the two it 'forgets' that the high bits aren't set (they might be set if there was intervening arithmetic).

Basically this meant I couldn't mark things as 'volatile', I had to use asm volatile("#comment\n":::"memory") instead - I used a fair number of those to change the instruction scheduling elsewhere.