[Bug tree-optimization/92429] [10 Regression] ICE in vect_transform_stmt, at tree-vect-stmts.c:10918

[avieira at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92429

--- Comment #2 from avieira at gcc dot gnu.org ---
So I had a look at this, the ICE occurs because 'vectorizable_condition' does
not know how to handle a constant cond_expr.

The reason this cond_expr is constant in the epilogue is because
'simplify_replace_tree' folds the replacement and the replacement in this case
is:

"_34 < 0" where "_34 = _33 * _33", and fold-const is able to assert that _34 is
therefore always positive or zero and can fold the check to false. The question
now is, why was the original 'cond_expr' that we copied over not folded? I
suspect its because of the -fno-tree-fre.

If we want this to work I suggest we either:
1) teach 'vectorizable_condition' to learn how to deal with constant
cond_expr's
2) change 'simplify_replace_tree' to optionally fold.

I don't like 2) much because this doesn't guarantee we don't fold elsewhere. 
If we want the vectorizer to accept loop code in sub-optimal format I suggest
we do 1).