MBB reordering vs. MBB fall-through

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#1

Hi,

Is it valid for an MBB to not have a final unconditional jump if the jump would be to the next MBB anyway? If yes, how is that supposed to interact with MBB reordering?

I'm asking because I've encountered a problem with the AVR backend where an MBB falls through to the wrong MBB due to reordering, and I'd like to know if the problem is having fall-throughs in the first place, or not communicating their presence somehow with other parts of LLVM.

Thanks,
   Gergo

#2

That is valid. Passes that want to reorder basic blocks should only do
so if the AnalyzeBranch and related target hooks (Insert/Remove) allow
it. They're capable of reconstructing the branches so they point to
arbitrary destinations.

Cheers.

Tim.