[LLVMdev] Comments on the bundle proposal

Krzysztof Parzyszek kparzysz at codeaurora.org
Thu Dec 8 08:36:18 PST 2011

On Wed, Dec 07, 2011 at 10:14:22AM -0800, Andrew Trick wrote:
> On Dec 6, 2011, at 3:10 PM, Krzysztof Parzyszek wrote:
> > - How about having bundles that contain branch targets (other than the
> > first instruction) from the outside of the bundle?  This seems like something
> > that has a potential for causing trouble, but I can't think of any specific
> > scenario at the moment.
> I think bundles could cross branches with some care. But I don't think they will ever be able to cross CFG merge points, if that's what you're asking.

Actually, what I was getting at was a clarification on whether the bundle
may or may not cross a basic block boundary.  While having a bundle that
contains a branch and a target of the branch may seem desirable, a bundle
that has a branch target (from outside) somewhere in the middle of it
seems to be a dangerous thing.  Evan's proposal didn't state any requirements
or limitations regarding that.  If there were no such limitations in place,
any generic code that is "bundle-aware" would need to take it into
consideration, possibly at the expense of complexity.


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