On Sunday, 16 November 2014 at 13:39:24 UTC, FrankLike wrote:
Many old projects need move from x86 to x64,but the 'length'
type is size_t,it will change on x64,so a lot of work must to
do.but I find some info which is help for d:
http://www.dotnetperls.com/array-length.
it means:
test length and longlength, and found 'test longlength' is
slower than 'test length'.
0.64 ns Length
2.55 ns LongLength
I love D.So I don't want my app on x64 slower than on x86.
Hope change in 2.067.
Thank you all.
At least on x86, I would recommand to cast size_t in "int" almost
everytime for speed.
- signed overflow is undefined behaviour and optimizers can take
advantage of it.
- 64-bits instructions on x86 takes more bytes to encode. i-cache
and instruction decoding suffer.
- 32-bits instructions on x86 fill the upper range with zeroes,
so that false dependencies are eliminated.
For these reasons 32-bits ops on x86 are more often than not
faster than "native"-sized int, opposite what intuition would
tell. For better or worse, int has been made the fastest integer
type by chip-makers.
