__shiftleft128

Article
06/05/2017

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Microsoft Specific**

Shifts a 128-bit quantity, represented as two 64-bit quantities LowPart and HighPart, to the left by a number of bits specified by Shift and returns the high 64 bits of the result.

Syntax

unsigned __int64 __shiftleft128(   
   unsigned __int64 LowPart,   
   unsigned __int64 HighPart,   
   unsigned char Shift   
);

Parameters

[in] LowPart
The low 64 bits of the 128-bit quantity to shift.

[in] HighPart
The high 64 bits of the 128-bit quantity to shift.

[in] Shift
The number of bits to shift.

Return Value

The high 64 bits of the result.

Requirements

Intrinsic	Architecture
`__shiftleft128`	x64

Header file <intrin.h>

Remarks

The Shift value is always modulo 64 so that, for example, if you call __shiftleft128(1, 0, 64), the function will shift the low part 0 bits left and return a high part of 0 and not 1 as might otherwise be expected.

Example

// shiftleft128.c  
// processor: IPF, x64  
#include <stdio.h>  
#include <intrin.h>  
  
#pragma intrinsic (__shiftleft128, __shiftright128)  
  
int main()  
{  
    unsigned __int64 i = 0x1I64;  
    unsigned __int64 j = 0x10I64;  
    unsigned __int64 ResultLowPart;  
    unsigned __int64 ResultHighPart;  
  
    ResultLowPart = i << 1;  
    ResultHighPart = __shiftleft128(i, j, 1);  
  
    // concatenate the low and high parts padded with 0's  
    // to display correct hexadecimal 128 bit values  
    printf_s("0x%02I64x%016I64x << 1 = 0x%02I64x%016I64x\n",  
             j, i, ResultHighPart, ResultLowPart);  
  
    ResultHighPart = j >> 1;  
    ResultLowPart = __shiftright128(i, j, 1);  
  
    printf_s("0x%02I64x%016I64x >> 1 = 0x%02I64x%016I64x\n",  
             j, i, ResultHighPart, ResultLowPart);    
}

0x100000000000000001 << 1 = 0x200000000000000002  
0x100000000000000001 >> 1 = 0x080000000000000000

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