[LLVMdev] The nsw story
clattner at apple.com
Thu Dec 1 09:09:22 PST 2011
On Dec 1, 2011, at 8:46 AM, Dan Gohman wrote:
> 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?
Please define "valid". We discussed this a very very long time ago, and I don't recall the details.
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