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Re: [PATCH][4.3] Deprecate -ftrapv
- From: Ken Raeburn <raeburn at raeburn dot org>
- To: Richard Guenther <rguenther at suse dot de>
- Cc: Mark Mitchell <mark at codesourcery dot com>, gcc-patches at gcc dot gnu dot org, gcc at gcc dot gnu dot org
- Date: Wed, 5 Mar 2008 17:45:47 -0500
- Subject: Re: [PATCH][4.3] Deprecate -ftrapv
- References: <Pine.LNX.firstname.lastname@example.org> <47C89DB1.email@example.com> <Pine.LNX.firstname.lastname@example.org>
On Feb 29, 2008, at 19:13, Richard Guenther wrote:
We wrap the libcalls inside libcall notes using REG_EQUAL notes
which indicate the libcalls compute non-trapping +-* (there's no
RTX code for the trappingness), so we combine and simplify the
operations making the libcall possibly dead and remove it again.
My patch from September (http://gcc.gnu.org/ml/gcc-patches/2007-09/
msg01351.html) should help with the libcall issue a bit, by making
the trapping libcalls not be considered dead, even if optimizations
make the results not get used. (Was I supposed to re-submit the
patch in non-unidiff format? I've had a couple of machine die on me
recently, I might have to reconstruct the source tree.) Of course,
if the trapping math is optimized away before you get to emitting
libcalls, that's a different bug.