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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/104645] [12 Regression] i ? i % 2 : 0 not
 optimized anymore
Date: Thu, 31 Mar 2022 13:09:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104645

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 52725
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52725&action=3Dedit
gcc12-pr104645.patch

I wonder if at least for GCC 13 we just can't treat even that cast stmt as a
preparation statement.
This won't handle say shifts etc. with casts after them, but will at least =
fix
this regression.
And for GCC 13 perhaps we can throw away all the separation of "preparation"
and assign statements and natural_element_p and absorbing_element_p and ins=
tead
just try to constant evaluate all the middle_bb statements and see if that
doesn't trigger traps/overflows/other UB and yields the expected PHI arg
constant from the original comparison constant.=