Reimplement some x86 intrinsics without arch-specific LLVM intrinsics #1807

Job	Run time
Check Style	24s
Env Override	17s
Automatic intrinsic verification	40s
Build std_detect	1m 32s
Build Documentation	1m 36s
Test (i686-unknown-linux-gnu)	3m 37s
Test (x86_64-unknown-linux-gnu)	6m 45s
Test (x86_64-unknown-linux-gnu-emulated)	15m 4s
Test (arm-unknown-linux-gnueabihf)	2m 37s
Test (armv7-unknown-linux-gnueabihf)	15m 59s
Test (aarch64-unknown-linux-gnu)	35m 38s
Test (riscv64gc-unknown-linux-gnu)	2m 30s
Test (powerpc64le-unknown-linux-gnu)	9m 3s
Test (s390x-unknown-linux-gnu)	2m 47s
Test (wasm32-wasi)	3m 38s
Test (i586-unknown-linux-gnu)	2m 57s
Test (nvptx64-nvidia-cuda)	41s
Test (thumbv6m-none-eabi)	16s
Test (thumbv7m-none-eabi)	21s
Test (thumbv7em-none-eabi)	24s
Test (thumbv7em-none-eabihf)	18s
Test (aarch64-apple-darwin)	2m 39s
Test (x86_64-pc-windows-msvc)	11m 58s
Test (i686-pc-windows-msvc)	6m 14s
Test (x86_64-apple-darwin, macos-11)	9m 47s
	2h 17m 42s

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