[LLVMdev] TargetDescription string

[Eli Friedman]

On Fri, Oct 26, 2012 at 5:11 PM, Preston Briggs
<preston.briggs at gmail.com> wrote:
> In "Writing an LLVM Compiler Backend", there's some discussion of the
> TargetDescription string, but it doesn't explain the examples I look
> at. For instance, in the description of the PowerPC, I see
>
>     "E-p:64:64-f64:64:64-i64:64:64-f128:64:128-n32:64"
>
> What's "preferred alignment" versus "ABI alignment"?
>
> What are the 3 figures following the "i"? (the documentation suggests
> there will only be 2).
>
> I see two entries for "f".  Do I read these as info about "f64" and "f128"?
>
> What is "n32:64" about?

http://llvm.org/docs/LangRef.html#datalayout

-Eli