[LLVMdev] New Configure Option for LLVM Builds

[Justin Holewinski]

On Jun 20, 2011, at 11:47 AM, John Criswell wrote:

> On 6/20/11 10:39 AM, Justin Holewinski wrote:
>> 
>> For the PTX back-end, I would like to introduce a configure-time option to determine the number of architectural registers available to LLVM register allocation during code generation.  The motivation for this is PTX is a virtual instruction set and the number of registers is configurable in the output file.  Thus, the number of registers specified via tablegen is arbitrary.  For different use-cases, it may be desirable to change this number.
> 
> Is it possible to make this option a command-line option to llc instead of a configure-time option?

Ideally, that would be the way to go.  However, as far as I know, LLVM requires static register data that is generated from tablegen files.  The only way I can think of changing this data is by automatically generating the tablegen files at configure time.

> 
> In my experience, it's better to make these options command-line options to tools when possible; that way, when someone wants to experiment with changing the parameter, they do not need to recompile.

I completely agree.  Unfortunately, I do not believe that is possible in this case (without major LLVM back-end changes).

> 
> -- John T.
> 

Thanks,

Justin Holewinski

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