On Sat, 21 Feb 2015 19:17:43 +0100
k0ga_AT_shike2.com wrote:
> > For 32 Bit / 64 Bit machines (assuming int is 32 bit and char is 8 bit).
> > Signed, unsigned makes no difference, assuming self-aligned (which is the
> > case on x86, x86_64 and ARM):
> If the char is signed you have to do bit sign extension, and for
> example transform 0x81 into 0xffffff81. Depend of the processor it
> can be done with only one instruction but in anothers you have to
> check the upper bit and branch based in its value. If the char is
> unsigned you always have to clear the upper bytes, so in the case of
> signed the code is longer and non linear (or even worse, the compiler
> calls an internal function to do the bit expansion).
You are absolutely right, but I was only talking about alignment-issues, not
arithmetic matters.
Cheers
FRIGN
--
FRIGN <dev_AT_frign.de>
Received on Sat Feb 21 2015 - 19:29:24 CET