[LLVMdev] On the transitivity of subregisterness
Jakob Stoklund Olesen
stoklund at 2pi.dk
Wed Apr 21 11:19:12 PDT 2010
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.
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