How to use __builtin_clzll in Rust? (count leading zeros)

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#1

GCC has the __builtin_clzll builtin function that according to https://www.geeksforgeeks.org/builtin-functions-gcc-compiler/:

__builtin_clz(x): This function is used to count the leading zeros of the integer. Note : clz = count leading zero’s

I think LLVM also has these functions, and Rust is compiled with LLVM. Is there a way to use this function in Rust?

#2

There's leading_zeros method on integers. It most likely compiles to the same thing. Use rust.godbolt.org to verify (remember to add -O to options on godbolt)

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#3

Indeed it does.

1 Like
#4

Moreover, it is implemented as direct call to the intrinsic.

1 Like
#5

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