Regression due to tree loop opt / expand weirdness

[Ulrich Weigand]

Richard Kenner wrote:
>     Would changing the test in expand_expr_addr_expr from 
>     
>       if (!target.valid_pointer_mode (tmode))
> 
>     to
> 
>       if (tmode != Pmode && tmode != ptr_mode)
> 
>     be OK with you?  This should cause no change to ia64 ...
> 
> That looks wrong to me.  On ia64, Pmode is always DImode, but ptr_mode can
> be either SImode or DImode depending on the *default* pointer size for
> the configuration.  But we want to support both 32-bit and 64-bit pointers
> for IA64 on at least some configurations (e.g., VMS) no matter what the
> default is.
> 
> The target.valid_pointer_mode test does exactly the right thing and seems
> to me to be the only thing that does.

First of all, the above change is provably a no-op on ia64 since
the valid_pointer_mode implementation on ia64 is the default one,
which is exactly (mode != Pmode && mode != ptr_mode).

In addition, if you look further down in expand_expr_addr_expr,
tmode is passed as argument to convert_memory_address, and this
routine by design allows only Pmode and ptr_mode as target mode.
If we pass in anything else, we get ICEs -- which is exactly 
the problem I had.  So if we indeed need to allow more modes at
some point, this will require much more extensive changes than
just this if condition.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  weigand@informatik.uni-erlangen.de