Hi Richard,

thanks for going through the patch set.

> A hash_set might be simpler, given that the code only enters insns
> for which the bool is false.  “rtx_insn *” would be better than rtx.

Right, changed that.

> Do you mean the sets might be removed or that the checks might be
> removed?

It's actually the checks that are removed.  I clarified and amended the 
comments.

> The patch is quite hard to review on its own, since nothing actually
> uses this variable.  It's also not obvious how the
> reg_overlap_mentioned_p code works if the old target is referenced
> later.
> 
> Could you refactor the series a bit so that each patch is
> self-contained? It's OK if that means fewer patches.
The attached v2 makes use of need_cmov now, I hope this makes it a bit 
clearer.  Regarding the reg_overlap_mentioned_p: it is used to detect 
the swap idioms as well as when a cmov destination is used in the 
condition as well.  If needed this could be two separate patches (most 
of the second patch would be comments, though).

Regards
  Robin