"For logical right shifts operands must have at ..."

[andreubotella]

For logical right shifts operands must have at least twenty-one bits precision.

Shouldn't this be for left shifts? After all, the result of a logical right shift will never have more bits than the larger of its operands.

[annevk]

Hmm, see https://lists.w3.org/Archives/Public/www-international/2014JulSep/0027.html and replies. That might have been wrong though.

[andreubotella]

I actually misread that sentence as talking about the result of right shifts, rather than to the operands, which is why I thought it must be referring to left shifts. But although that message is indeed right in that bit shifts do depend on the size of the input, that only makes a difference for logical right shifts of negative numbers:

// Arithmetic right shifts
8 (i8) >> 1 = 4
8 (i16) >> 1 = 4
8 (i32) >> 1 = 4
-8 (i8) >> 1 = -4
-8 (i16) >> 1 = -4
-8 (i32) >> 1 = -4

// Logical right shifts
8 (i8) >>> 1 = 4
8 (i16) >>> 1 = 4
8 (i32) >>> 1 = 4
-8 (i8) >>> 1 = 124
-8 (i16) >>> 1 = 32764
-8 (i32) >>> 1 = 2147483644

And since the only right shifts in the standard have code points or code units as their input, they must be positive.

[annevk]

Okay, I would be fine dropping that sentence. I've been kinda hoping we can remove the majority of that section once whatwg/infra#87 is sorted.

[andreubotella]

Closing this in the meantime, then.