YOSHIFUJI Hideaki / 吉藤英明 wrote:
In article <[EMAIL PROTECTED]> (at Fri, 21 Dec 2007 07:03:58 +0100), Eric Dumazet
<[EMAIL PROTECTED]> says:
Because tot_len is signed in tcp_v6_send_ack(), tot_len/4 forces compiler
to emit an integer divide, while we can help it to use a right shift,
less expensive.
Are you really sure?
At least, gcc-4.1.2-20061115 (debian) does not make any difference.
Quite true -- thus it is a matter of taste to the programmer. Constant
folding inside the compiler ensures that "foo / 4" asm output is just as
optimal as a shift.
And, IMHO, because shift for signed variable is fragile, so we should
avoid using it.
I respectfully disagree, but this is an unrelated matter. As you say,
"/4" is fine as-is.
Jeff
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