MEM_NONTRAP_P and push/pop alias set (Was: Re: [attn port maintainers] fix 23671)

[Joern RENNECKE]

Richard Henderson wrote:

>  
>
>As a practical short-term concern, rtx_addr_can_trap_p will not return
>true for any stack based reference, including push/pop.  So for 4.1, 
>nothing need be done.  Longer term, the answer to the "what does notrap
>  
>
Actually, the SHcompact save / restores use neither stack  nor frame 
pointer in
their MEMs.  

>>a specific alias set.  We already have gen_const_mem for readonly
>>memory, so maybe that could be gen_pushpop_mem.
>>    
>>
>
>I agree completely.  This should be done before a lot of target
>code gets uglified.
>  
>
Hmm, I've just found we already have a get_frame_alias_set.  So I'm 
working on
a patch to for a new function get_frame_mem, which sets MEM_NOTRAP_P
and sets the alias set to get_frame_alias_set (), and to use this in all 
the places
of the target-independent code where get_frame_alias_set is currently used
(unless the address looks fishy).
There are many more places in the target-specific code, but I can't 
really test all
the targets, so I'll leave patching that code up to the target maintainers.