On Friday, 2 November 2012 at 10:24:34 UTC, Jens Mueller wrote:
Then I have a serious misunderstanding.
I thought D introduced array operations to allow the compiler to
generate efficient vector operations (in the long run), i.e.
generate
SIMD code. Why is this not working out?
It works fine for large vectors. For small vectors, it is
horrendously slow.
The syntax a[] += b[] essentially calls a function which is
designed to work for large vectors. It has to determine
alignment, load everything from memory, do the operations, then
store it back.
The SIMD extensions allow you to define variables that are
guaranteed to be aligned and will probably be in the right
registers to start with. Using them, the vectors ops don't need
to determine alignment, and often don't need to do lots of
loads/stores.
Both have their purposes.
