> On Oct 17, 2016, at 12:26 PM, Bin.Cheng <amker.ch...@gmail.com> wrote:
> On Sat, Oct 15, 2016 at 3:07 AM, kugan
> <kugan.vivekanandara...@linaro.org> wrote:
>> Hi Bin,
>> On 15/10/16 00:15, Bin Cheng wrote:
>>> +/* Test for likely overcommitment of vector hardware resources. If a
>>> + loop iteration is relatively large, and too large a percentage of
>>> + instructions in the loop are vectorized, the cost model may not
>>> + adequately reflect delays from unavailable vector resources.
>>> + Penalize the loop body cost for this case. */
>>> +static void
>>> +aarch64_density_test (struct aarch64_vect_loop_cost_data *data)
>>> + const int DENSITY_PCT_THRESHOLD = 85;
>>> + const int DENSITY_SIZE_THRESHOLD = 128;
>>> + const int DENSITY_PENALTY = 10;
>>> + struct loop *loop = data->loop_info;
>>> + basic_block *bbs = get_loop_body (loop);
>> Is this worth being part of the cost model such that it can have different
>> defaults for different micro-architecture?
> I don't know. From my running, this penalizing function looks like a
> quite benchmark specific tuning. If that's the case, tuning for
> different micro architecture may not give meaningful different
> results, at the cost of three parameters.
> Hi Bill, I guess you are the original author? Do you recall any
> motivation of this code or have some comments? Thanks very much.
> Meanwhile, I can do some experiments on different AArch64 processors.
Yes, this is specific tuning due to problems observed on a
POWER model. I don't necessarily recommend this approach for
other architectures without appropriate experimental verification