[Bug middle-end/81876] [7/8 Regression] bogus -Wstrict-overflow warning with -O3

law at redhat dot com gcc-bugzilla@gcc.gnu.org
Mon Dec 4 23:38:00 GMT 2017


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81876

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |law at redhat dot com

--- Comment #2 from Jeffrey A. Law <law at redhat dot com> ---
I'm a bit unsure how you want to proceed here Richi.

Marc's changes to move key folding patterns from fold-const.c into match.pd
means the x + 1 > x  -> 1 simplification happens earlier/more often.  So the
problematical sequence gets wiped out by VRP2.   That's probably a good thing.  

However, that bit of match.pd does not warn when it makes that assumption.  
One could argue it should.  Of course if it warns, then we end up in situations
like this BZ where the warning spit out by GCC bears no resemblance to the
actual source code because of ldist or other significant code transformations.

So I could make an argument to drop the 8 from the regression marker.  I could
make an argument we should open a new BZ for the missed warning and/or a BZ for
getting the code coming out of ldist sane.

Thoughts?


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