gcc4.7.2: try/finally, CLOBBER

[Ian Lance Taylor]

On Thu, May 30, 2013 at 2:07 AM, Vini Kanvar <vini@cse.iitb.ac.in> wrote:
>
> gcc-4.7.2 adds exception handling constructs (try/finally block) for
> pointer and array variables. These variables are CLOBBERed in the
> finally block.

I'm not sure what you mean by this.  An example might help.

> What is the meaning and use of CLOBBER? In which cases is it required?
> What will happen if gcc does not CLOBBER these variables (e.g.
> gcc-4.6.2 does not add try/finally and CLOBBER in the gimple code. How
> does gcc-4.6.2 deal with such variables?).

In RTL CLOBBER simply means that the value is unimportant and
meaningless.  If a CLOBBER is omitted it means that GCC will 1)
preserve the value in the register; 2) assume that the value in the
register has been preserved.

Ian