CryptoPkg/Library/IntrinsicLib/Ia32/MathLShiftS64.c

   1 /** @file
   2   64-bit Math Worker Function.
   3   The 32-bit versions of C compiler generate calls to library routines
   4   to handle 64-bit math. These functions use non-standard calling conventions.
   5
   6 Copyright (c) 2014, Intel Corporation. All rights reserved.<BR>
   7 SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 /*
  12  * Shifts a 64-bit signed value left by a particular number of bits.
  13  */
  14 __declspec(naked) void __cdecl
  15 _allshl (
  16   void
  17   )
  18 {
  19   _asm {
  20     ;
  21     ; Handle shifting of 64 or more bits (return 0)
  22     ;
  23
  24     cmp     cl, 64
  25     jae     short ReturnZero
  26
  27     ;
  28     ; Handle shifting of between 0 and 31 bits
  29     ;
  30     cmp     cl, 32
  31     jae     short More32
  32     shld    edx, eax, cl
  33     shl     eax, cl
  34     ret
  35
  36     ;
  37     ; Handle shifting of between 32 and 63 bits
  38     ;
  39 More32:
  40     mov     edx, eax
  41     xor     eax, eax
  42     and     cl, 31
  43     shl     edx, cl
  44     ret
  45
  46 ReturnZero:
  47     xor     eax,eax
  48     xor     edx,edx
  49     ret
  50   }
  51 }