Re: [PATCH][4.3] Deprecate -ftrapv

[Ken Raeburn <raeburn at raeburn dot 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.