http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47920
--- Comment #3 from Carrot <carrot at google dot com> 2011-03-01 06:44:47 UTC --- (In reply to comment #1) > Presumably because arithmetic right-shift by 3 isn't the same as a division by > 8 when (a+7) is negative. Changing the types to unsigned gives the code you > want. You are right. Right shift and division are different for negative numbers. Thumb1 uses a different code sequence since it doesn't support conditional execution t08: add r0, r0, #7 asr r3, r0, #31 lsr r3, r3, #29 add r0, r3, r0 asr r0, r0, #3 bx lr If we use the similar code sequence in thumb2 we can reduce one instruction because the logical shift and the following add can be merged into one instruction t08: add r0, r0, #7 asr r3, r0, #31 add r0, r0, r3, LSR #29 asr r0, r0, #3 bx lr I wonder if this will be faster.