[Help-smalltalk] Re: [Lightning] Code patching, context switching

[Paolo Bonzini]

> That's unfortunate. Is there a good reason for this artificial
> limitation? Seems Lightning would be much more flexible as a code
> generator with a low-level interface, which is what I assumed
> JIT_R/V/FPR were, and a higher-level interface, which is what
> jit_getarg and jit_prolog are. I can understand wanting to insulate
> the users from inadvertently clobbering the argument registers, but a
> low-level api would still be nice.

The problem is that jit_pusharg needs to clobber r3-r9, and it would be 
an unnecessarily complication to say "this and that JIT_Rx register" are 
clobbered by jit_pusharg, but only on this and that architecture".  If 
you're building your own RA, you can just use integers from 0 to 31 (on 
PPC) and forget about JIT_R/JIT_V completely.

In general, lightning was thought more for template-based code generation.

Paolo