[llvm-dev] getCacheSize() implementation (retrieving subtarget id) (original) (raw)

Nemanja Ivanovic via llvm-dev llvm-dev at lists.llvm.org
Thu Nov 30 02:38:48 PST 2017

Hi Jonas, on PPC we store the "ID for the CPU" in what we call a "DarwinDirective" (the name is likely to change in the future). The idea is that the CPU identifies itself to the Subtarget through a feature. Then you can easily query the CPU ID through that feature.

For details, you can see PPCTTIImpl::getCacheLineSize(). P.S. I imagine that after so long, you've found the solution yourself (or come up with a different one). I am sorry, but I've been falling behind on llvm-dev emails this fall so some have slipped by.

On Tue, Oct 17, 2017 at 4:48 PM, Jonas Paulsson via llvm-dev < llvm-dev at lists.llvm.org> wrote:

Hi,

While trying to implement the SystemZTTI::getCacheSize() method, it became clear that a simple way of retrieving the machine ID is somehow missing. It seems that the Subtarget should set a variable during initialization perhaps by looking at the CPU string. I would like to hear any opinion on how this would actually be best implemented. * Comparing the CPU string seems to duplicate SystemZProcessors.td in the sense that it would ideally be sufficient to only specify the CPU string once. * Extend ProcessorModel with a "processor model ID" that the Subtarget could later retrieve? * Or instead extend MCSchedModel with the ID, or even store the cache size / assosiativity in MCSchedModel? / Jonas

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