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Re: RFC: PATCH to gimplify_modify_expr_rhs to make return slot explicit
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Mark Mitchell <mark at codesourcery dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Richard Henderson <rth at redhat dot com>
- Date: Wed, 12 Jan 2005 21:52:38 -0500
- Subject: Re: RFC: PATCH to gimplify_modify_expr_rhs to make return slot explicit
- Organization: Red Hat Canada
- References: <email@example.com>
Jason Merrill wrote:
Any thoughts?Not an objection to the patch, but this will also cause TBAA to
introduce more alias relations with the variable in the return slot.
The aliasing code will not only see it as an addressable variable, but
will also consider it call-clobbered.
I'm not sure how much of a problem this is, but it should be easy to
measure by checking the .alias dumps before/after the patch. We
obviously need to make the aliaser smarter (law and dberlin are working
on enhancements that should help, though they may not be ready for 4.0).