Re: PING: PATCH [9/n]: Prepare x32: PR middle-end/47383: ivopts miscompiles Pmode != ptr_mode

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Jul 5, 2011 at 7:42 AM, Ulrich Weigand <uweigand@de.ibm.com> wrote:
> Richard Guenther wrote:
>
>> That doesn't look correct without also ensuring we never create a
>> TARGET_MEM_REF with a base that is not in the default address-space.
>> In fact, with this patch the address-space argument to addr_for_mem_ref
>> should go away or we need a hook that provides a non-promoted mode
>> for address-spaces.
>>
>> Uli?
>
> Common code should basically *never* directly refer to Pmode or ptr_mode;
> instead it should always use the per-address-space modes
> ? targetm.addr_space.address_mode (as)
> or
> ? targetm.addr_space.pointer_mode (as)
>
> The "address_mode" is the mode to handle addresses at the instruction level
> (i.e. the mode of the address within a MEM (or TARGET_MEM_REF)). ?This
> defaults to Pmode for the default address space.

Here is the problem.  For x32, Pmode is the "address_mode".  But
TARGET_MEM_REF only works on ptr_mode, not Pmode unless Pmode
is the same as ptr_mode.

> The "pointer_mode" is the mode to handle pointers at source level. ?This
> defaults to ptr_mode for the default address space.
>
> [ Note that there is one exception: common code today continues to hard-
> code Pmode for addresses known to refer to the stack; the stack must lie
> in the default address space at this point. ]
>
> So the patch below, changing targetm.addr_space.address_mode (as) to
> just "ptr_mode" is definitely wrong and will break multiple address
> spaces. ?If at this point indeed a pointer mode is required, you should
> use targetm.addr_space.pointer_mode (as) instead.

I will give it try.

> However, this still seems odd to me, as I had understood the address in
> a TARGET_MEM_REF needs to be an *address*, i.e. use address_mode. ?If
> this is not true (has changed?) a lot of other places would need to
> change as well ...

I was told that TARGET_MEM_REF needs ptr_mode.

Thanks.

-- 
H.J.