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>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/


/*
 * 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
  }
}