[Bug target/115749] Non optimal assembly for integer modulo by a constant on x86-64 CPUs

[kim.walisch at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115749

--- Comment #4 from kim.walisch at gmail dot com ---
One possible explanation for why GCC's current integer division by a constant
assembly sequence was chosen back in the day (I guess one or two decades ago)
is that GCC's current assembly sequence uses only 1 mul instruction whereas
Clang uses 2 mul instructions.

Historically, multiplication instructions used to be slower than add, sub and
shift instructions on nearly all CPU architectures and so it made sense to
avoid mul instructions whenever possible. However in the past decade this
performance gap has narrowed and now it is more important to avoid long
instruction dependency chains which GCC's current integer modulo by a constant
assembly sequence suffers from.