[PATCH] Allow 0-weight branches in BranchProbabilityInfo.

[Diego Novillo]

On Wed, May 6, 2015 at 10:46 AM, Duncan P. N. Exon Smith
<dexonsmith at apple.com> wrote:
>
>> On 2015 May 6, at 13:39, Diego Novillo <dnovillo at google.com> wrote:
>>
>>
>>
>> On 05/06/15 13:37, Hans Wennborg wrote:
>>> On Wed, May 6, 2015 at 10:09 AM, Duncan P. N. Exon Smith
>>>
>>> Are you saying you don't want to guarantee that anymore, or that
>>> forcing each weight <= UINT32_MAX / SI.getNumSuccessors() is
>>> unnecessarily strict?
>>
>> Yeah, I've wanted to remove this restriction for some time. The only requirement we really need is that the sum of all the weights fits within 32 bits.
>>
>> I'm going to be removing this restriction in http://reviews.llvm.org/D9442
>
> You'll have to leave it in place until the downstream consumers stop
> flooring the weights at 1, but as long as there's a plan for lifting
> the restriction I'm happy.

Well, currently BPI wants each branch weight to fit UINT32_MAX /
successors, but in D9442, I will implement your suggestion of fitting
weights such that Sum(weights) < UINT32_MAX.  This assert() may start
triggering after my change.


Diego.