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

[Michael Gottesman]

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?
> 
> 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? 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).
> 

I will let John McCall take this one.

> Also, almost all uses of "LLVM" in this document refer to the
> language/IR/"VM", rather than "the LLVM libraries/project" [1]; I
> think this distinction is important to uphold (admittedly, it probably
> ought to be clarified). I would thus prefer avoiding a phrase like
> "LLVM optimizes", and opt for something more neutral like "Global
> initializers may assume that ...". Note how other parts of this
> section merely say that what they specify "enables better
> optimization" (or something like that). A less neutral rationale can
> also be added (see r174007 for an example).
> 
> [1] e.g. in the first paragraph "LLVM is a Static Single Assignment
> (SSA) based representation that provides type safety, low-level
> operations, flexibility, and the capability of representing ‘all’
> high-level languages cleanly. It is the common code representation
> used throughout all phases of the LLVM compilation strategy."

Ok I can make that change.

> 
> -- Sean Silva