[llvm-commits] [llvm] r76215 - /llvm/trunk/include/llvm/Value.h

[Dan Gohman]

On Jul 18, 2009, at 1:06 PM, Duncan Sands wrote:


> Hi Dan,
>
>
>> This optional data is information like "signed overflow is  
>> undefined".
>>
>
> why is this set up as optional data?  Shouldn't it be a full blown  
> flag
> on the operation, analogous to a parameter attribute?

The design idea here is that these are flags which are not necessary for
correctness. A "signed add" is not a different operation from an "add";
it's just an "add" with some value-range information that the optimizer
may find useful.

Dan