[PATCH] D76483: [DivRemPairs] Freeze operands if they can be undef values

Sat Mar 21 00:29:42 PDT 2020

aqjune added a comment.

I assessed the performance impact by running test-suite & comparing generated assemblies before/after this patch, and found that only there was only one such assembly file.
It was SingleSource/Regression/C/gcc-c-torture/execute/scal-to-vec1.c  , and I could find that freeze was not simplifying vector constant with non-undef integers. I'll update https://reviews.llvm.org/D76010 to cover it.

> Just to check my understanding of current behavior: the freeze insts will survive to SelectionDAGBuilder, and there they get removed?

Yes, freeze is simply removed when lowering to SelDag.
The relevant patch is https://reviews.llvm.org/D29014 . I was postponing to landing it to master because MachineIR people didn't accept the patch.
I think it is a good idea to splitting the patch D29014 <https://reviews.llvm.org/D29014> to cover only SelDag first. What do you think?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76483/new/

https://reviews.llvm.org/D76483