[Hexagon] Enable depthwise conv2d NHWC with an HWIO kernel layout

[farshidsp]

This PR adds support for depthwise_conv2d_NHWC with an HWIO kernel layout.

@Lunderberg @mehrdadh

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• cc @Icemist, @ibsidorenko, @mehrdadh _{See #10317 for details}

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[Lunderberg]

I like the feature, but I'm not quite following how the permutation specified results in a HWIO kernel layout.

[Lunderberg]

The explicit __getitem__ isn't required. Filter[x,y,z] is syntactic sugar for Filter[(x,y,z)]. If you already have a tuple, then Filter[tuple( ... )] can be called.

[farshidsp]

Oh I see, I have changed this as your recommendation.

[Lunderberg]

I'm not seeing how this permutation generates HWIO. This defines kernel_permutation_to as [3, 2, 0, 1], so kernel_permutation_from is [2, 3, 1, 0]. With the usage below, that would permute from [di, dj, c//channel_multiplier, c%channel_multiplier] to [c//channel_multiplier, c%channel_multiplier, dj, di], which would be OIWH.

Should this be list(range(dim)) + [dim + 1, dim] instead?

[farshidsp]

@Lunderberg You are right, my bad. Not sure why I thought this would result in HWIO. Thanks so much for catching this bug.

[Lunderberg]

Is there a benefit to defining in terms of kernel_permutation_to instead of directly defining kernel_permutation_from?

[farshidsp]

I tried to follow this as much as possible so in the future we can add more features if needed. If you think this is not the best way I could change it.

[Lunderberg]

Ah, I see. It looks like that implementation is trying to be more clever, and to identify the permutation by inspecting the string. In this case, since we're only supporting two explicitly enabled shapes, I'd lean for defining a kernel_permutation directly for each one.

if kernel_layout == 'HWOI':
    kernel_permutaiton = [0,1,2,3]
elif kernel_layout == 'HWIO':
    kernel_permutaiton = [0,1,3,2]
else:
    raise ValueError(f'Unsupported kernel layout: {kernel_layout}')

[Lunderberg]

That said, if there are many locations where the same kernel permutation definitions are used, it may be useful to pull it out into a common utility.

[farshidsp]

Changed the way of permutation from your recommendation. @Lunderberg

[TejashShah]

@farshidsp Is kernel layout or filter layout a better word to indicate the change in layout?

[farshidsp]

@farshidsp Is kernel layout or filter layout a better word to indicate the change in layout?

In other topi files, we have used kernel_permutation to indicate the change in the kernel layout and that's why I used the same term.

[Lunderberg]

Thank you for making the changes, and LGTM!