Summary:
As [[ https://bugs.llvm.org/show_bug.cgi?id=45360 | PR45360 ]] reports,
with new cost-model we can sometimes end up being able to expand `udiv`/`urem` instructions.
And that exposes at least one instance of when we do that
regardless of whether or not it is safe to do.
In this particular case, it's `SimplifyIndvar::replaceIVUserWithLoopInvariant()`.
It seems to me, we simply need to check with `isSafeToExpandAt()` first.
The test isn't great. I'm not sure how to make it only run `-indvars`.
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=45360 | PR45360 ]].
Reviewers: mkazantsev, reames, helloqirun
Reviewed By: mkazantsev
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82108
https://bugs.llvm.org/show_bug.cgi?id=45360
This is reduced from the (runnable) test provided in the bug report.
The remainder operation is originally guarded, it never divides by zero.
Indvars should not make it execute unconditionally.
This is not a great test, running whole -O2 is fragile,
but i really don't understand why running -indvars on the IR before
that tranform happens doesn't work.
Roman Lebedev