[llvm-commits] [llvm] r83082 - /llvm/trunk/include/llvm/ADT/StringRef.h

[Daniel Dunbar]

On Mon, Oct 12, 2009 at 10:16 AM, Devang Patel <dpatel at apple.com> wrote:
> OK. I'll update how DebugInfo uses StringRef.

Hi Devang,

Has this been done? The original patch here is still in StringRef and
I think it should go away.

 - Daniel

> -
> Devang
> On Oct 12, 2009, at 7:02 AM, Daniel Dunbar wrote:
>
> Yes, this isn't something that should be in StringRef, I would go so far to
> say this is an invariant clients can rely on:
> --
> StringRef(a).data() == a
> --
> As Chris mentions we want the StringRef constructors to be simple, we use
> them a lot and rely on the optimizer to clean them up, for example in
> default arguments. It's good to avoid any unnecessary complexity.
>  - Daniel
>
> On Sep 29, 2009, at 9:59 PM, Chris Lattner wrote:
>
> On Sep 29, 2009, at 11:57 AM, Devang Patel wrote:
>
> On Sep 29, 2009, at 11:53 AM, Chris Lattner wrote:
>
> On Sep 29, 2009, at 11:39 AM, Devang Patel wrote:
> Author: dpatel
>
> Date: Tue Sep 29 13:39:56 2009
>
> New Revision: 83082
>
> URL: http://llvm.org/viewvc/llvm-project?rev=83082&view=rev
>
> Log:
>
> Create empty StringRef is incoming cstring is NULL.
>
> I don't think this is correct, StringRef shouldn't allow null cstrings to be
> passed in.
>
> I'm using it to pass optional strings. For example, linkage name in debug
> info.
> Note, one can create empty StringRef by say
> SringRef foo;
> If this is not desirable then I'll update DebugInfo interface.
>
> The reason I mention that is that stringref is frequently used for const
> char*'s, and this adds an extra branch to the common case.  Doing something
> like:
>   return ptr != 0 : StringRef(ptr) : StringRef();
> in the debug info stuff would make it pay the cost locally instead of making
> all clients of stringref pay it.
> What do you think Daniel?
> BTW, getting rid of std::string from debug info is really really awesome!
> -Chris
>
>
>
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