Reduce fdiv's into fmul's #868

Job	Run time
Build and test cmake:gcc9	31s
Build and test cmake:clang15	37s
Build and test cmake:clang15:asan	47s
Build and test cmake:clang15:tsan	48s
Build and test cmake:clang15:ubsan	56s
Build and test cmake:qemu-arm-neon-gcc	58s
Build and test cmake-osx:clang	21s
Build and test cmake-osx:gcc	29s
Build and test cmake-win64:msvc-rel	1m 22s
Build and test cmake-win64:msvc-dbg	1m 0s
Build and test fuzz:clang15	37s
Build and test python3.10:clang15	1m 53s
Build and test python3.10-win	55s
Build and test maven	26s
Build and test bazel:root	38s
Build and test bazel:go	28s
Build and test bazel:java	2m 15s
Build and test bazel:research	24s
Build and test bazel-osx:root	1m 6s
Build and test bazel-osx:go	1m 2s
Build and test bazel-osx:java	2m 13s
Build and test bazel-osx:research	1m 2s
Build and test bazel-win:root	50s
Build and test bazel-win:java	3m 1s
Build and test bazel-win:research	51s
	25m 30s

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