CryptoPkg/Library/IntrinsicLib/Ia32/MathLShiftS64.c

/** @file
  64-bit Math Worker Function.
  The 32-bit versions of C compiler generate calls to library routines
  to handle 64-bit math. These functions use non-standard calling conventions.

Copyright (c) 2014, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

/*
 * 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
  }
}