[LLVMdev] predicates and Requires

[reed kotler]

Well, Requires is just a fancy way to add predicates.

For mips16 and micro mips, we want to use them in a similar way as ARM 
does, I think, to how they
are used for thumb and thumb2.

The problem lies with tablegen.

Whenever predicates are overriden by a derived class, it overwrites the 
previous definition.

There is no way, it seems, to add to an existing list as you further 
derive classes.

So for example, for mips we would want to have several predicates for 
the output format
of instructions, i.e. (standard, mips16, micromips)

But if we have such predicates in a base class, then if some later class 
wants to add additional ones,
then they have to list the ones from the base class again.

This seems to be very error prone.

Is there some basic convention that the ARM port uses to keep all of 
this straight?

Tia.

Reed