MathLShiftS64.c

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/*
 * Shifts a 64-bit signed value left by a particular number of bits.
 */
__declspec(naked) void __cdecl
_allshl (
  void
  )
{
  _asm {
    ;
    ; Handle shifting of 64 or more bits (return 0)
    ;
 
    cmp     cl, 64
    jae     short ReturnZero
 
    ;
    ; Handle shifting of between 0 and 31 bits
    ;
    cmp     cl, 32
    jae     short More32
    shld    edx, eax, cl
    shl     eax, cl
    ret
 
    ;
    ; Handle shifting of between 32 and 63 bits
    ;
More32:
    mov     edx, eax
    xor     eax, eax
    and     cl, 31
    shl     edx, cl
    ret
 
ReturnZero:
    xor     eax,eax
    xor     edx,edx
    ret
  }
}