[llvm-dev] LLC does not do proper copy propagation (or copy coalescing)

[陳韋任 via llvm-dev]

>
>     I see 3 options to address my problem:
>       - implement a case that handles this in PHI elimination
> (PHIElimination.cpp);
>       - create a new pass that does copy propagation (based on DFA) on
> machine instructions before Register Allocation;
>       - optimize copy coalescing such as the standard one or the one
> activated by -pbqp-coalescing in lib/CodeGen/RegAllocPBQP.cpp (there is an
> email also about PBQP coalescing at http://lists.llvm.org/pipermai
> l/llvm-dev/2016-June/100523.html).
>

Usually this is done by copy coalescing, do you know why yours cannot be
eliminated, is your case not be handled well in existing copy
coalescing (RegisterCoalescer.cpp
for example)?

​HTH,
chenwj​

-- 
Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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