[PATCH 1/3] Add new keyword externally_initialized to LLVM.

[Michael Gottesman]

Ok. So how does this sound John/Sean:

I will commit this patch and prepare a second patch with the clarification paragraph and post it here.

Michael

On Feb 1, 2013, at 4:36 PM, John McCall <rjmccall at apple.com> wrote:

> On Feb 1, 2013, at 3:01 PM, Sean Silva <silvas at purdue.edu> wrote:
>> +By default, LLVM optimizes global initializers by assuming that global
>> +variables defined within the module are not modified from their
>> +initial values before the start of the global initializer.
>> 
>> Is this assumption documented anywhere else in LangRef?
> 
> I don't think so.  I agree that it ought to be;  I'm not sure where.
> 
>> If not, then this creates a normative specification about the
>> semantics of globals in LLVM IR. I'm not saying whether that is good
>> or bad, but is it intentional?
> 
> It is at least the apparent existing semantics of IR.  Arguably the default
> semantics ought to be reversed, but that would be a very invasive change.
> 
>> If so, I would rather add this specification in a separate patch fixing the
>> omission (it is essentially fixing a documentation bug (unspecified aspect
>> of the language); no need to confuse that change with adding a new
>> language feature).
> 
> This is a fair point.
> 
> John.