[LLVMdev] The nsw story

[Dan Gohman]

On Nov 30, 2011, at 10:49 PM, Chris Lattner wrote:

> 
> On Nov 29, 2011, at 3:21 PM, Dan Gohman wrote:
> 
>> 
>> A natural reaction to this problem is to think that LLVM IR is so nice
>> and pretty that naturally there must be a nice and pretty solution. Here
>> are some alternatives that have been considered:
>> 
>> - Go back to using undef for overflow. There were no known real-world
>>  bugs with this. It's just inconsistent.
> 
> +1 for the simple and obvious answer.

To be clear, the main sign-extension elimination optimization is not valid under
the simple and obvious answer.  Are you proposing to do it anyway?

Dan