[Bug tree-optimization/46172] [4.3/4.4/4.5/4.6 Regression] ICE: in expand_widen_pattern_expr, at optabs.c:522 with -ftree-vectorize -fno-tree-dce

["irar at il dot ibm.com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46172

--- Comment #5 from Ira Rosen <irar at il dot ibm.com> 2010-11-02 13:28:14 UTC ---
(In reply to comment #4)
> Ah, if this is in dead code created by vectorizer that really shouldn't be ever
> expanded,

Yes, in this case it's dead code created by the vectorizer that shouldn't be
expanded. But there is also always scalar code that we do not remove except for
stores.

> then either we need to arrange for DCE to be performed after
> vectorizer even if flag_tree_vectorize && !flag_tree_dce (e.g. by using a
> different pass structure e.g. instead of pass_dce_loop and use a different gate
> for it right after vectorizer), 

Yes, this is what I meant.


> or vectorizer shouldn't create garbage.
> 
> -fno-tree-dce is sometimes useful for compiler testing to write testcases e.g.
> for expansion and RTL passes bugs, so making it unconditional is not a good
> idea.