Re: gcc's autovectorizer tests

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

> test2.c:9: note: not vectorized: unhandled data ref: D.1452_8 = b[i_5].x
> test2.c:6: note: vectorized 0 loops in function.

GCC does not know what to do with structs yet.

For the third one, one would also need to implement recognition of 
if-converted idioms (there's something on autovect branch, but the 
design of if-conversion is very unclear to me).

Or, more complete phi optimization with tree codes for saturated 
addition and subtraction.  This would be effective in non-vectorized 
code as well.

Paolo