VTA/debugging vs reload-v2

[Jeff Law]

On 04/06/10 00:35, Jakub Jelinek wrote:
> On Mon, Apr 05, 2010 at 05:18:35PM -0600, Jeff Law wrote:
>    
>>> 2. When renaming references from P to P' in a region, do take debug
>>> insns in the region into account, renaming references in debug insns as
>>> you would in any other insn.
>>>
>>>        
>> OK.  So presumably the 2nd argument in a VAR_LOCATION can be any rtl
>> expression?  Meaning I have to parse it looking for things that need
>> changing?    Right?
>>      
>    The problematic stuff is mainly when some RTL
> with non-VOIDmode (REG, MEM etc.) needs to be replaced with a VOIDmode
> constant - in that case simplify_replace_{,fn_}rtx needs to be used to
> change the invalid RTL into valid.
These shouldn't be a problem.


>     But I guess for reload2 you'll be
> changing just REGs and MEMs to other REGs and MEMs - in that case
> just a replacement through say for_each_rtx is possible too.
>    
Yea, we're going to have to walk down the expression with for_each_rtx 
searching for REGs, then see if the REG we found needs replacing.  
Handling narrowing SUBREGs makes this marginally more complex, but it's 
still manageable.  I just wanted to be sure there that there weren't any 
assumptions I could make to simplify the code :-)

jeff