[LLVMdev] On the transitivity of subregisterness

Evan Cheng evan.cheng at apple.com
Wed Apr 21 14:36:55 PDT 2010

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?



> 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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