https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85551
Bug ID: 85551
Summary: No strength reduction of modulo and integer vision
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: linux at carewolf dot com
Target Milestone: ---
Created attachment 44030
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44030&action=edit
strmod.cpp
Many simple loops using modulo naively can be optimized too not perform the
expensive module/division every iterations, but GCC does not perform this
strength reduction.
I have attached a motivating example including two iterations of optimizations.
An easy safe one (though it might interfere with vectorization if the arch has
vectorized integer divisions), and a more agressive one that is much faster in
some cases but not always.
