[Bug rtl-optimization/92712] [8/9/10 Regression] Performance regression with assumed values
glisse at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri Nov 29 14:52:00 GMT 2019
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92712
--- Comment #8 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #6)
> The suggestion I'll try to work on is to check if C isn't a plus/minus expr
> with constant second operand that doesn't go in the other direction and thus
> where the transformation isn't introducing UB.
In the testcase, t-1 is computed in some unsigned type and then cast back to
signed, so I don't think it will work.
> I guess it should be enough to do this in match.pd though.
Yes.
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