Optimizing byte-swap-and-store on PPC

[Paul Cercueil]

Hi Paulo,

If you remember, I added an optimization (for my use case anyway) for
the following code:

jit_ldr(rY, rX);
jit_bswapr(rY, rY);

Lightning will only generate a single LWBRX instruction for this.

Now I would like to do the same for stores. The problem is that the
pattern typically use a temporary register T:

jit_bswapr(T, rX);
jit_str(rY, T);

How can I know that the register T is dead after this pattern?

Cheers,
-Paul