Refactor conv 3 #5695

Job	Run time
apple (aarch64-apple-ios)	2m 8s
apple (aarch64-apple-darwin)	2m 44s
linux (raspbian)	6m 42s
linux (aarch64-unknown-linux-gnu)	11m 35s
linux (armv6vfp-unknown-linux-gnueabihf)	10m 3s
linux (armv7-unknown-linux-gnueabihf)	10m 19s
linux (aarch64-unknown-linux-musl)	12m 16s
linux (armv7-unknown-linux-musl)	10m 0s
linux (aarch64-linux-android)	1m 13s
linux (armv7-linux-androideabi)	1m 24s
linux (i686-linux-android)	1m 20s
linux (x86_64-linux-android)	1m 11s
linux (wasm32-unknown-unknown)	28s
linux (wasm32-wasi)	29s
	1h 11m 52s

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