[Dwarf-Discuss] Representing the location of smaller values in vector registers

Michael Eager eager at eagercon.com
Wed Mar 9 11:35:04 PST 2016


On 03/09/2016 11:26 AM, Frank Ch. Eigler wrote:
> Hi -
>
> On Wed, Mar 09, 2016 at 11:20:38AM -0800, Michael Eager wrote:
>> [...]
>> Variable definitions describe where the variable is defined.
>> If the size of the variable is different from the size of
>> the container, it should be described as such.
>>
>> This has nothing to do with location lists.
>
> ... except to the extent that the same variable may have different
> containers, so representation base-types, at different code locations?

When a variable (say an 8-bit char) is loaded into a 32-bit
register, the location list can represent that the *value* can
now be found in that register.  That does not mean that the
allocation for the variable has changed, nor does DWARF
create multiple descriptions for a variable which may (at
certain times in it's lifetime) be loaded into a register.

Location lists and variable declarations are orthogonal.
Adrian's DWARF excerpt was for a variable declaration;
most of the discussion has been about location lists.

-- 
Michael Eager	 eager at eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077


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