"(1 << $firstbit)" seems to be a constant. Extract it from the loop and it should be faster.

You could remove the loop completely by (in the case of 32 bit) checking the high-bit, then shifting for $y, then or-ing with $FFFFFFFF shifted left 32-$y

In reply to Re: Implementing a signed/sign-propagating right bitwise shift by jethro
in thread Implementing a signed/sign-propagating right bitwise shift by LonelyPilgrim

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