This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Designs for better debug info in GCC
On Dec 19, 2007, "Daniel Berlin" <dberlin@dberlin.org> wrote:
> Here is the easy one:
> z_5 = a_3 + b_3
> x_4 = z_5 + c_3
> DEBUG(x, x_4)
> Reassoc may transform this into:
> z_5 = c_3 + b_3
> x_4 = z_5 + a_3
> DEBUG(x, x_4)
> Now x has the wrong value.
As Andrew said, no, it doesn't.
Now, if z_5 were present in a debug expression, then it would need
adjusting. No different from the adjusting need for any other
instruction in which z_5 was present, though. That's what I mean when
I talk about letting the optimizers do their job on debug instructions
too.
--
Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member http://www.fsfla.org/
Red Hat Compiler Engineer aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist oliva@{lsd.ic.unicamp.br, gnu.org}