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Re: Designs for better debug info in GCC

On Dec 20, 2007, Ian Lance Taylor <> wrote:

> Alexandre Oliva <> writes:
>> > How do i know i need to change this DEBUG expression.
>> As reassoc looks for sets of variables it can freely mess with, it
>> should take note of variables that are used in debug annotations in
>> addition to the kind of single (?) non-debug uses it's interested in,
>> such that, when it modifies these variables, the annotations can be
>> compensated for.

> The question is how it finds them efficiently, without doing a scan of
> all instructions.

It must keep track of variables it can mess with, so it might as well
take notes about those it has to be more careful about.

*Or* it can just introduce new temporaries, rename the uses and leave
the original sets behind for "garbage collection" AKA dead code
elimination, like I said.

One is more implementation work, the other is potentially more
wasteful in terms of memory use.  None look particularly hard to me.

Alexandre Oliva
FSF Latin America Board Member
Red Hat Compiler Engineer   aoliva@{,}
Free Software Evangelist  oliva@{,}

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