[LLVMdev] On the transitivity of subregisterness

[Evan Cheng]

On Apr 21, 2010, at 11:19 AM, Jakob Stoklund Olesen wrote:

> Woud it be reasonable to assert that TargetRegisterInfo::isSubRegister() is a transitive relation?

Yes.

Evan

> 
> In other words, if A is a subregister of B and B is a subregister of C then A is a subregister of C.
> 
> With this assumption, we could teach TableGen to sort registers topologically such that all the subregisters of R are numbered R+1, R+2, ... This produces better locality of reference and allows other optimizations in the backend code that deals in subregisters a lot.
> 
> /jakob
> 
> 
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