BPF: backport commit 51cdb780db3b9b46c783efcec672c4da272e9992

[yonghong-song]

Bugzilla Link	49400
Resolution	FIXED
Resolved on	May 10, 2021 14:27
Version	unspecified
OS	All
Blocks	#48661
CC	@4ast,@tstellar
Fixed by commit(s)	51cdb78 6564e0c

Extended Description

I would like to backport the following BPF backend commit in llvm13 trunk
to llvm 12.0.1:

51cdb78 BPF: Fix a bug in peephole TRUNC elimination optimization

This fixed a compiler core dump error in certain cases.

[4ast]

Makes sense. Approved

[tstellar]

Merged: 6564e0c