[wasm] Add maxPool kernel.

[annxingyuan]

Changes

• Implement maxPool wasm kernel that calls into XNNPACK
• Short circuit maxpool if window is [1,1] and input/output shape match

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This change is 

[Maratyszcza]

Reviewable status: 0 of 1 approvals obtained (waiting on @annxingyuan, @dsmilkov, and @Maratyszcza)

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tfjs-backend-wasm/src/cc/kernels/MaxPool.cc, line 83 at r1 (raw file):

        flags, &max_pool_op);

    if (status != xnn_status_success) {

If xnn_create_max_pooling2d_nhwc_f32 fails, the function should exit early, because max_pool_op is nullptr, and it is not safe to call xnn_setup_max_pooling2d_nhwc_f32 and xnn_run_operator with a nullptr

[dsmilkov]

Awesome!

Reviewed 6 of 9 files at r1, 3 of 3 files at r2.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @annxingyuan and @dsmilkov)

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tfjs-backend-wasm/src/setup_test.ts, line 42 at r2 (raw file):

    include: 'maxPool',
    excludes: [
      'f=[1,1]',          // XNN does not support filter height and width of 1.

since you short-circuit 1x1 case, reenable this test?

[annxingyuan]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @dsmilkov and @Maratyszcza)

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tfjs-backend-wasm/src/setup_test.ts, line 42 at r2 (raw file):

Previously, dsmilkov (Daniel Smilkov) wrote…

since you short-circuit 1x1 case, reenable this test?

There is still a f=[1,1] test that does not pass the short circuiting condition.

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tfjs-backend-wasm/src/cc/kernels/MaxPool.cc, line 83 at r1 (raw file):

Previously, Maratyszcza (Marat Dukhan) wrote…

If xnn_create_max_pooling2d_nhwc_f32 fails, the function should exit early, because max_pool_op is nullptr, and it is not safe to call xnn_setup_max_pooling2d_nhwc_f32 and xnn_run_operator with a nullptr

Done