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From: "aagarwa at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/36010] Loop interchange not performed
Date: Mon, 16 Oct 2023 12:40:07 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D36010

Ajit Kumar Agarwal <aagarwa at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aagarwa at gcc dot gnu.org

--- Comment #5 from Ajit Kumar Agarwal <aagarwa at gcc dot gnu.org> ---
Use the following flags-fassociative-math -fno-signed-zeros -fno-trapping-m=
ath
to make loop-interchange work.

Following code in gcc/gimple-loop-interchange.cc
@@ -514,8 +514,8 @@ loop_cand::analyze_iloop_reduction_var (tree var)
       if (! (associative_tree_code (code)
             || (code =3D=3D MINUS_EXPR
                 && use_p->use =3D=3D gimple_assign_rhs1_ptr (ass)))
         || (FLOAT_TYPE_P (TREE_TYPE (var))
           && ! flag_associative_math))
         return false;
     }
   else

Because of the flag_associative_math conditions at line no: 514 it returns
false and loop interchange doesn't work. Using the above flags make
flag_associative_math as true and loop interchange works.=