[LLVMdev] Undoing DAG Combiner patterns

[Martin Filteau]

Hi all,

It's the first LLVM backend we do for our asynchronous DSP. So, I apologize if this is a trivial question!

The target-independent DAG combiner performs the following transformation:

sub  n, c                ->  add n, -c

For our target, negative constants are more costly to encode.  What is the best place to revert to a sub instruction?

Kind regards,

-- Martin

www.octasic.com<http://www.octasic.com>



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