Int64ShllMod32 macro (winnt.h)
Performs a left logical shift operation on an unsigned 64-bit integer value. The function provides improved shifting code for left logical shifts where the shift count is in the range 0-31.
Syntax
void Int64ShllMod32(
[in] a,
[in] b
);
Parameters
[in] a
The unsigned 64-bit integer to be shifted.
[in] 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 left logical shift operation on an unsigned value, the value's bits move to the left, and vacated bits on the right side of the value are set to zero.
A compiler can generate optimal code for a left 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 Int64ShllMod32 function lets the compiler generate optimal or near-optimal code.
Please note that the Int64ShllMod32 function's Value parameter and return value are 64-bit values, not LARGE_INTEGER structures.
Requirements
| Requirement | Value |
|---|---|
| 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) |