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Re: unwind info for epilogues
- From: Richard Henderson <rth at redhat dot com>
- To: Ian Lance Taylor <iant at google dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 29 May 2009 17:49:40 -0700
- Subject: Re: unwind info for epilogues
- References: <4A01F133.email@example.com> <firstname.lastname@example.org>
Ian Lance Taylor wrote:
This approach seems clearly superior. I wonder if you can provide some
simple functions for the backends to call to add notes and such.
Possibly. At the moment I can't really think of any, or at least
anything more complicated than the existing add_reg_note. I would
expect these to become more apparent as ports are converted.
> One could also imagine a more complex function which simply walked the
prologue and did something like what the current dwarf2out.c code does,
except adding reg notes. That might make it relatively easy to
transition the backends to the new scheme.
This same thought occurred to me. Combine that with tracking the CFA
state across basic block boundaries, and markers for the CFA state to
be placed at hot/cold section boundaries and we'll fix two outstanding
bugs with unwind code.
Now if only someone would rewrite delayed-branch opt to not hork the
CFG, and the aforementioned pass will be easy...