[PATCH] powerpc: Add helper functions for synthesising instructions at runtime

[Paul Mackerras]

Michael Ellerman writes:

> +typedef enum {
> +	BRANCH_RELATIVE,
> +	BRANCH_RELATIVE_LINK,
> +	BRANCH_ABSOLUTE,
> +	BRANCH_ABSOLUTE_LINK
> +} branch_t;

Just to pursue this thread a bit further...

I think your branch_t is folding together two things that are really
orthogonal, and this is causing your code to get longer and more
confusing than necessary.

I would just have defined two separate flags, say BRANCH_ABSOLUTE and
BRANCH_LINK (either with #define or enum), and then declared the
"type" argument to create_branch as "bitwise".  Then you can simply OR
the type argument into the instruction word, and you can do tests like
if (!(type & BRANCH_ABSOLUTE)) quite naturally.

This ends up being almost exactly what Segher suggested, but maybe
a little less obfuscated.

Paul.