[llvm-commits] PATCH: Teach the function cloner to prune dead basic blocks

[Duncan Sands]

On 28/03/12 02:49, Chandler Carruth wrote:
> Ping.

LGTM.  Did you do some compile time testing?

Ciao, Duncan.

>
> On Sun, Mar 25, 2012 at 1:21 PM, Chandler Carruth <chandlerc at gmail.com
> <mailto:chandlerc at gmail.com>> wrote:
>
>     On Sun, Mar 25, 2012 at 12:17 PM, Chris Lattner <clattner at apple.com
>     <mailto:clattner at apple.com>> wrote:
>
>         WeakVH is *substantially* more expensive than AssertingVH.  The later is
>         just a raw pointer when assertions are disabled.
>
>
>     Yep, but that's not what this patch changes. The value map is currently
>     using a *TrackingVH*, not an AssertingVH. My understanding is that
>     TrackingVH isn't substantially less expensive than WeakVH. Both have to be
>     updated on RAUW. WeakVH has to be updated on delete as well, but this patch
>     adds the first delete operations.
>
>         The former requires densemap operations when a WeakVH is modified.
>
>         Why is it expensive to update the value mapping?
>
>
>     We have to update everything that maps *to* the deleted instructions. That's
>     a full walk of the value map for each instruction deleted.
>
>
>
>
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