Window scheduler ignores IMPLICIT_DEF instructions

[Zararest]

Description

I was working with window scheduler and found confusing part in its algorithm.
On the line llvm/lib/CodeGen/WindowScheduler.cpp:300 WindowScheduler copies region to schedule, but ignores meta instructions one of which is IMPLICIT_DEF. Because of this all uses of IMPLICIT_DEF have no definition. This results in assertion later in code.

I created a reproduction for Hexagon, but I am not sure whether this code is correct. Probably, there are other examples where IMPLICIT_DEF and its use are in the same basic block, but I could not find them.

Reproduction

bash ./run.txt

run.txt

pipeliner-assert.txt

Debug build fails with assertion.