The Int64ShraMod32 function performs a right arithmetic shift operation on a signed 64-bit integer value. The function provides improved shifting code for right arithmetic shifts where the shift count is in the range 0 - 31.
LONGLONG Int64ShraMod32(
| LONGLONG Value, | // specifies signed 64-bit integer to shift right arithmetically |
| DWORD ShiftCount | // specifies a shift count in the range 0 - 31 |
| ); |
Parameters
Value
Specifies the signed 64-bit integer to be shifted.
ShiftCount
Specifies a shift count in the range 0 - 31.
Return Values
The return value is the signed 64-bit integer result of the right arithmetic shift operation.
Remarks
The shift count is the number of bit positions that the value's bits move.
In a right arithmetic shift operation on a signed value, the value's bits move to the right, and vacated bits on the left side of the value are set to the value of the sign bit.
A compiler can generate optimal code for a right arithmetic 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 Int64ShraMod32 function lets the compiler generate optimal or near-optimal code.
Please note that the Int64ShraMod32 function's Value parameter and return value are 64-bit values, not LARGE_INTEGER structures.
See Also