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Re: PR 23551: why should we coalesce inlined variables?
On Jul 9, 2007, Michael Matz <matz@suse.de> wrote:
> You somehow keep forgetting SSA form.
No, I'm just reporting the result of the optimizations I'm seeing.
Early SSA coalescing is not the end of it. The assignment to foo_2
*does* go away, and if we don't introduce some means to preserve its
location in a way that doesn't hurt optimization, we won't be able to
emit correct debug info for foo.
> An SSA name _is_ a range for exactly the value that it holds initially.
Yes. It's a range for the value. But not for the multiple variables
that may end up holding that value. In my example, you'll find cases
in which it both starts too early and ends too late WRT the variable
that holds that value at some point.
--
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}