[Bug tree-optimization/106343] SLP does not support no-op case

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106343

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I should note that I noticed LLVM does not handle this either.

Basically the following operators and values can be used:
For integer:
+ 0
- 0
* 1
/ 1
| 0
& -1 (all ones)
^ 0

For floating point (only with -ffast-math, I think sub can be used with 0 and
add with -0.0 without but I am not 100% sure):
+ 0
- 0
* 1
/ 1