On Thu, Oct 11, 2012 at 02:44:12PM -0700, Teresa Johnson wrote:
> Revised patch to address conservative behavior in redundant extend
> elimination that was resulting in redundant extends not being
> removed. Now uses a new target hook machine_mode_from_attr_mode
> which is currently enabled only for i386.
I still don't like it, the hook still is about how it is implemented
instead of what target property it wants to ask (the important thing
there is that a {QI,HI} -> SImode zero extension instruction on x86_64
performs {QI,HI} -> DImode extension actually). That isn't the case for any
other modes, isn't the case for sign extension etc.
Can you please post a testcase first?
Given the recent ree.c changes to remember the performed operations and
their original modes (struct ext_modified), perhaps the
"Second, make sure the reaching definitions don't feed another and"...
check could be made less strict or even removed, but for that a testcase is
really needed.
Jakub
