Re: [patch] fix regrename pass to ensure renamings produce valid insns

[Eric Botcazou <ebotcazou@adacore.com>]

> The attached patch teaches regrename to validate insns affected by each
> register renaming before making the change.  I can see at least two
> other ways to handle this -- earlier, by rejecting renamings that result
> in invalid instructions when it's searching for the best renaming; or
> later, by validating the entire set of renamings as a group instead of
> incrementally for each one -- but doing it all in regname_do_replace
> seems least disruptive and risky in terms of the existing code.

OK, but the patch looks incomplete, rename_chains should be adjusted as well, 
i.e. regrename_do_replace should now return a boolean.

-- 
Eric Botcazou