On 15/03/2024 12:47 PM, Basile B. wrote:
On Thursday, 14 March 2024 at 23:39:33 UTC, Liam McGillivray wrote:
On Thursday, 14 March 2024 at 01:58:46 UTC, Richard (Rikki) Andrew
Cattermole wrote:
[...]
I tried to rework the functions to use bitwise operations, but it was
difficult to figure out the correct logic. I decided that it's not
worth the hassle, so I just changed the value storage from `bool[3]`
to `ubyte`. Now it works much more like your version.
https://github.com/LiamM32/Open_Emblem/blob/c2014ab3f77e89c0cedcd6dbf7f8362ebfac33a9/source/common.d
I did a little reading, so now I understand what it means when you
have `&= 7`. But I want to ask, is this faster than `%= 8`? If not, I
would like to change it to the latter for readability.
`%=8` will be codegened using slower intructions w/o optimz enabled but
with `&=7` you directly get the right instruction, which does not
involves integer division. See https://godbolt.org/z/74vbba5aG
Yes, it'll depend upon how smart the compiler is at optimizing and it
may not occur in non-optimizing builds.
The modulas instructions are based upon division, this is an incredibly
expensive operation.
https://stackoverflow.com/a/8022107
The division instruction on Haswell for integers ranges from 9 cycles
for 8bit, all the way up to 36 cycles for 64bit.
