[Bug tree-optimization/64024] [5 Regression] gcc.dg/vect/vect-simd-clone-6.c ICEs

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64024

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jakub at gcc dot gnu.org

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
So, the problem is that we have during vector analysis:

<bb 9>:
# i_33 = PHI <0(8), i_25(11)>
# ivtmp_27 = PHI <1024(8), ivtmp_26(11)>
_17 = (unsigned short) i_33;
_18 = _17 * 3;
_20 = (int) _18;
_22 = a[i_33];
_23 = foo (_22, pretmp_38, _20);
c[i_33] = _23;
i_25 = i_33 + 1;

and simple_iv returns true for _20, despite the (unsigned short) cast in there,
as 0 * 3 nor 1023 * 3 overflows.  But during vector transform phase the bb is
already:

<bb 9>:
# i_33 = PHI <i_46(28), i_25(11)>
# ivtmp_27 = PHI <ivtmp_49(28), ivtmp_26(11)>
# vect_vec_iv_.213_89 = PHI <vect_cst_.211_87(28), vect_vec_iv_.213_90(11)>
# vectp_a.219_100 = PHI <vectp_a.220_98(28), vectp_a.219_101(11)>
vect_vec_iv_.213_90 = vect_vec_iv_.213_89 + vect_cst_.212_88;
vect_vec_iv_.213_92 = vect_vec_iv_.213_89 + vect_cst_.214_91;
vect__17.215_93 = VEC_PACK_TRUNC_EXPR <vect_vec_iv_.213_89,
vect_vec_iv_.213_92>;
_17 = (unsigned short) i_33;
vect__18.216_95 = vect__17.215_93 * vect_cst_.217_94;
_18 = _17 * 3;
vect__20.218_96 = [vec_unpack_lo_expr] vect__18.216_95;
vect__20.218_97 = [vec_unpack_hi_expr] vect__18.216_95;
_20 = (int) _18;
vect__22.221_102 = MEM[(int *)vectp_a.219_100];
vectp_a.219_103 = vectp_a.219_100 + 16;
vect__22.222_104 = MEM[(int *)vectp_a.219_103];
_22 = a[i_33];
_23 = foo (_22, pretmp_38, _20);
c[i_33] = _23;
i_25 = i_33 + 1;

and in that case a) not sure if SCEV knows that the loop max bound is still
1024 b) as the initial value for i is an SSA_NAME, not constant, it also
doesn't know it behaves as proper linear variable.