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[mecej4]

Paul, please consider adding new intrinsic functions that make the X64 instructions LEADZ, TRAILZ and POPCNT available to the Fortran programmer. There are several situations where such a function call can replace an entire DO loop. For example, given an integer variable v, if we wish to divide by the largest power of 2 possible, we could do

nz=trailz(v)
if(nz > 0) v = ishft(v,nz)

instead of writing a loop:

WHILE (MOD(v,2).eq.0) DO
v = v/2
END DO

Thank you.
Of course, these new intrinsics are feasible only when targeting X64.

[PaulLaidler]

mecej4
Thank you for the feedback. I will add these to the wish list.

[mecej4]

Thanks, Paul.
The trailz function is also useful in deciding whether a four digit year is a leap year.

[mecej4]

Gfortran, Intel Fortran, Absoft Fortran and NAG Fortran provide TRAILZ as an intrinsic function.

Another application for TRAILZ is in rapid calculation of Collatz sequences. I am curious to know if anyone on this forum has toyed with the Collatz Conjecture.

[Kenneth_Smith]

The functions TRAILZ, LEADZ, and POPCNT (and also POPPAR) are listed as intrinsic functions in the 2008 standard.

[mecej4]

Thanks, Kenneth, and I have no excuse for not being aware of those additions to F2008 in 2025, other than not running into an instance of one of them being beneficial in a Fortran program.