Int64ShrlMod32 macro

Performs a right logical shift operation on an unsigned 64-bit integer value. The function provides improved shifting code for right logical shifts where the shift count is in the range 0-31.

Syntax

void Int64ShrlMod32(
   a,
   b
);

Parameters

a

The unsigned 64-bit integer to be shifted.

b

The shift count in the range 0-31.

Return Value

None

Remarks

The shift count is the number of bit positions that the value's bits move.

In a right logical shift operation on an unsigned value, the value's bits move to the right, and vacated bits on the left side of the value are set to zero.

A compiler can generate optimal code for a right logical shift operation when the shift count is a constant. However, if the shift count is a variable whose range of values is unknown, the compiler must assume the worst case, leading to non-optimal code: code that calls a subroutine, or code that is inline but branches. By restricting the shift count to the range 0-31, the Int64ShrlMod32 function lets the compiler generate optimal or near-optimal code.

Note  The Int64ShrlMod32 function's Value parameter and return value are 64-bit values, not LARGE_INTEGER structures.
 

Requirements

   
Minimum supported client Windows XP [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header winnt.h (include Windows.h)

See Also

Int64ShllMod32

Int64ShraMod32

Large Integers