[llvm-commits] [llvm] r115255 - /llvm/trunk/docs/LangRef.html

[Chris Lattner]

On Sep 30, 2010, at 7:42 PM, Nick Lewycky wrote:

>> There was indeed some code assuming you could make a zero of any type.  I changed it.
>> 
>> The whole point of this type is that the optimizers are not allowed to manipulate it.  They should not be creating undefs or constants of this type either.
> 
> Sure, but tools like bugpoint will try to eliminate instructions by 
> replacing their uses with undef. How painful would it be to make 'x86mmx 
> undef' legal?

The mmx type does need to be a value type.  This implies that it should support "zeroinitializer", "undef" phi nodes, by-value parameter passing, etc.

-Chris