Refactor conv 3 #5697

Job	Run time
apple (aarch64-apple-ios)	1m 25s
apple (aarch64-apple-darwin)	2m 42s
linux (raspbian)	6m 56s
linux (aarch64-unknown-linux-gnu)	11m 48s
linux (armv6vfp-unknown-linux-gnueabihf)	10m 16s
linux (armv7-unknown-linux-gnueabihf)	10m 7s
linux (aarch64-unknown-linux-musl)	12m 51s
linux (armv7-unknown-linux-musl)	10m 39s
linux (aarch64-linux-android)	1m 21s
linux (armv7-linux-androideabi)	1m 59s
linux (i686-linux-android)	1m 5s
linux (x86_64-linux-android)	1m 12s
linux (wasm32-unknown-unknown)	29s
linux (wasm32-wasi)	27s
	1h 13m 17s

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