Refactor conv #5672

Job	Run time
apple (aarch64-apple-ios)	4m 6s
linux (raspbian)	6m 59s
linux (aarch64-unknown-linux-gnu)	12m 43s
apple (aarch64-apple-darwin)	3m 21s
linux (armv6vfp-unknown-linux-gnueabihf)	10m 26s
linux (armv7-unknown-linux-gnueabihf)	10m 32s
linux (aarch64-unknown-linux-musl)	11m 26s
linux (armv7-unknown-linux-musl)	10m 12s
linux (aarch64-linux-android)	1m 34s
linux (armv7-linux-androideabi)	1m 24s
linux (i686-linux-android)	1m 31s
linux (x86_64-linux-android)	1m 27s
linux (wasm32-unknown-unknown)	39s
linux (wasm32-wasi)	32s
	1h 16m 52s

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