EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/LShiftU64.asm

   1 ;/*++
   2 ;
   3 ;Copyright (c) 2006, Intel Corporation
   4 ;All rights reserved. This program and the accompanying materials
   5 ;are licensed and made available under the terms and conditions of the BSD License
   6 ;which accompanies this distribution.  The full text of the license may be found at
   7 ;http://opensource.org/licenses/bsd-license.php
   8 ;
   9 ;THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 ;WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11 ;
  12 ;Module Name:
  13 ;
  14 ;  LShiftU64.c
  15 ;
  16 ;Abstract:
  17 ;
  18 ;  64-bit left shift function for IA-32
  19 ;
  20 ;--*/
  21 ;
  22 ;---------------------------------------------------------------------------
  23     .686
  24     .model  flat,C
  25     .code
  26
  27 ;---------------------------------------------------------------------------
  28 ;
  29 ;UINT64
  30 ;LShiftU64 (
  31 ;  IN UINT64   Operand,
  32 ;  IN UINTN    Count
  33 ;  )
  34 ;/*++
  35 ;
  36 ;Routine Description:
  37 ;
  38 ;  This routine allows a 64 bit value to be left shifted by 32 bits and
  39 ;  returns the shifted value.
  40 ;  Count is valid up 63. (Only Bits 0-5 is valid for Count)
  41 ;
  42 ;Arguments:
  43 ;
  44 ;  Operand - Value to be shifted
  45 ;  Count   - Number of times to shift left.
  46 ;
  47 ;Returns:
  48 ;
  49 ;  Value shifted left identified by the Count.
  50 ;
  51 ;--*/
  52 LShiftU64 PROC
  53
  54     mov    eax, [esp + 4]; dword ptr Operand[0]
  55     mov    edx, [esp + 8]; dword ptr Operand[4]
  56
  57     ;
  58     ; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EAX is not touched
  59     ; For CL of 32 - 63, it will be shifted 0 - 31 so we will move eax to edx later.
  60     ;
  61     mov    ecx, [esp + 0Ch]; Count
  62     and    ecx, 63
  63     shld   edx, eax, cl
  64     shl    eax, cl
  65
  66     ;
  67     ; Since Count is 32 - 63, eax will have been shifted  by 0 - 31
  68     ; If shifted by 32 or more, set lower 32 bits to zero.
  69     ;
  70     cmp    ecx, 32
  71     jc     short _LShiftU64_Done
  72
  73     mov    edx, eax
  74     xor    eax, eax
  75
  76 _LShiftU64_Done:
  77
  78     ret
  79 LShiftU64 ENDP
  80         END