On Wednesday, 12 October 2016 at 12:46:50 UTC, Andrei
Alexandrescu wrote:
On 10/12/2016 06:56 AM, Stefan Koch wrote:
I just confirmed that branching version is faster then
table-lookup.
please test it our for yourself
http://paste.ofcode.org/3CpieAhkrTYEcSncbPKbrj
The table-lookup does produce the smallest code though.
Nice. I like that the table is NOT looked up on the ASCII path,
so it stays cold in ASCII text. However, there's a problem with
this pattern:
size_t char_length = 1;
immutable c = s[0];
if (c < 192)
{
Lend :
s = s.ptr[char_length .. s.length];
return ;
}
as opposed to:
immutable c = s[0];
if (c < 192)
{
Lend :
s = s.ptr[1 .. s.length];
return ;
}
In the second case, the compiler generates an inc for bumping
the pointer and a dec for decreasing the length (small
instructions). If the variable char_length is used, add/sub
must be used (larger). -- Andrei
btw.
We could get rid of of a sub if we changed slices from holding a
pointer and a length to holding two pointers.
