[llvm-dev] [GlobalISel] Questions about selection regions

Bekket McClane via llvm-dev llvm-dev at lists.llvm.org
Tue Jan 31 07:12:42 PST 2017

I've been studying the global instruction selector introduced recently. One
of the properties of global instruction selectors is that they select
instructions across basic blocks such that they can get more information in
order to choose optimal patterns.
However, the current global isel implementation still iterates over BBs
within functions, which is same as the original SelectionDAG approach, and
select individual instruction without "peeking" the information of other
basic blocks. IMOO, neither do the overall design nor the individual
instruction selector routines take the "global information" into concern.
Are my observations correct?
Also, are there any examples which show that the current global isel take
information across multiple BBs within a function?

Best Regards,
Bekket McClane
Department of Computer Science,
National Tsing Hua University
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