[Openmp-dev] Performance killer: more registers are used when multiple target regions are compiled together

[Ye Luo via Openmp-dev]

Hi all,
I just found when there are multiple offload regions, all the finally
assembled kernels use equal amount registers corresponding to the kernel
that uses the most registers. This causes all my kernels spilling registers
and thus kills performance. This is surprising and I didn't see this
behavior with IBM XL compiler.
The reproducer is provided at https://bugs.llvm.org/show_bug.cgi?id=46450
I also noticed the same issue with AOMP.
So I'm wondering where could potentially be buggy in the compiling/linking
flow.
Any thoughts?
Best,
Ye
===================
Ye Luo, Ph.D.
Computational Science Division & Leadership Computing Facility
Argonne National Laboratory
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