Re: [PATCH, i386, Pointer Bounds Checker 33/x] MPX ABI

[Jeff Law <law at redhat dot com>]

On 09/23/14 00:31, Ilya Enkovich wrote:
> I did this change a couple of years ago and don't remember exactly
> what problem was caused by PARALLEL.  But from my comment it seems
> parallel lead to values in BND0 and BND1 not to be actually defined by
> call from DF point of view.  I'll try to reproduce a problem I had.
Please do.  That would indicate a bug in the DF infrastructure.  I'm not 
real familiar with the DF implementation, but a quick glance at 
df_def_record_1 seems to indicate it's got support for a set destination 
being a PARALLEL.

> > This kind of scheme also doesn't tend to "play well" with exception handling
> > & scheduling becuase you can't guarantee the sets and the call are in the
> > same block and scheduler as a single group.
>
> How can the sets and  the call no be in the same block/group if all of
> them are parts of a single instruction?
Obviously in the cases where we've had these problems in the past they 
were distinct instructions.  So EH interactions isn't going to be an 
issue for MPX.

However, we've still got the problem that the RTL you've generated is 
ill-formed.  If I understand things correctly, the assignments are the 
result of the call, that should be modeled by having the destination be 
a PARALLEL as mentioned earlier.



Jeff