[llvm] r185883 - Fix a bug in IRBuilder::ClearInsertionPoint. The IR Builder needs to reset both the BB and the insert point inside the BB.

[Eric Christopher]

Interesting, sure, makes sense.

Thanks!

-eric

On Mon, Jul 8, 2013 at 5:17 PM, Nadav Rotem <nrotem at apple.com> wrote:
> The problem is that there are lots of exit points, and you don’t want to
> manually restore the IRBuilder location at each one of them. The function
> vectorizerTree alone has 13 exit points, because we try to reduce compile
> time and break out as early as possible.
>
> On Jul 8, 2013, at 5:11 PM, Eric Christopher <echristo at gmail.com> wrote:
>
> *looks at code*
>
> Aha. Interesting. Why not just save the instruction that you'd like to
> insert at on the side (or a stack of such if that's what's going on)?
> I'm not clear on what BuilderLocGuard is doing other than the saving
> of the instruction off to the side, but I admit that I've not looked a
> whole lot :)
>
> -eric
>
> On Mon, Jul 8, 2013 at 5:06 PM, Nadav Rotem <nrotem at apple.com> wrote:
>
> SetInsertPoint does set both, but the GetInsertPoint returns only the
> Instruction (and not the BB).  I ran into this with the RAII class that
> saves the IRBuilder location.  Actually, Alexey's ASan bot helped me
> discover it :)
>
>
> On 07/08/13, Eric Christopher <echristo at gmail.com> wrote:
>
> On Mon, Jul 8, 2013 at 4:27 PM, Nadav Rotem <nrotem at apple.com> wrote:
>
> Author: nadav
> Date: Mon Jul  8 18:27:43 2013
> New Revision: 185883
>
> URL: http://llvm.org/viewvc/llvm-project?rev=185883&view=rev
> Log:
> Fix a bug in IRBuilder::ClearInsertionPoint. The IR Builder needs to reset
> both the BB and the insert point inside the BB.
>
>
> I'd run into this in the past and didn't think much of it because all
> of the SetInsertPoint routines set both variables. How'd you run into
> this?
>
> -eric
>
>