VTA/debugging vs reload-v2

Jakub Jelinek jakub@redhat.com
Tue Apr 6 06:36:00 GMT 2010

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?

Yes, it can be arbitrary valid RTL (validate_change/verify_changes allow
any changes to DEBUG_INSNs).  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.  We don't want say
(zero_extend:DI (const_int 6)) or (subreg:QI (const_int 12345678) 4) etc.
staying around in the DEBUG_INSNs.  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.


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