[LLVMdev] initial selection DAG

listiges at arcor.de listiges at arcor.de
Tue Oct 16 05:24:06 PDT 2012


sorry for my late reply. You were right. Something was missed in the xxxLowering.cpp.

Thank you! 

Kind regards,

----- Original Nachricht ----
Von:     Tim Northover <t.p.northover at gmail.com>
An:      listiges at arcor.de
Datum:   12.10.2012 11:39
Betreff: Re: [LLVMdev] initial selection DAG

> Hi Nico,
> > I miss three nodes and I wonder what do I have to implement to get at
> least the right initial selection DAG?
> Most of the work is done by the files in lib/CodeGen/SelectionDAG
> (first SelectionDAGBuilder.cpp, then the Legalizers and DAGCombiner) .
> However, various target-specific hooks are used during the process
> (the biggest handling function-calls and formal parameters). These
> hooks and the data that effect them are defined in
> lib/Target/XXX/XXXISelLowering.cpp
> What should the nodes you're missing be doing? It's difficult to say
> quite what part of ISelLowering you need to look at without knowing
> that.
> > Do I have to define all instructions in the td files first?
> No. In principle you should be able to get a fully correct selection
> dag without defining a single instruction. It wouldn't be much use for
> most targets, but it would exist.
> Tim.

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