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

   1 #/*++
   2 #
   3 #Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
   4 #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 #include "EfiBind.h"
  23 #---------------------------------------------------------------------------
  24     .686:
  25     #.MODEL flat,C
  26     .code:
  27
  28 #---------------------------------------------------------------------------
  29 .globl ASM_PFX(LShiftU64)
  30 #
  31 #UINT64
  32 #LShiftU64 (
  33 #  IN UINT64   Operand,
  34 #  IN UINTN    Count
  35 #  )
  36 #/*++
  37 #
  38 #Routine Description:
  39 #
  40 #  This routine allows a 64 bit value to be left shifted by 32 bits and
  41 #  returns the shifted value.
  42 #  Count is valid up 63. (Only Bits 0-5 is valid for Count)
  43 #
  44 #Arguments:
  45 #
  46 #  Operand - Value to be shifted
  47 #  Count   - Number of times to shift left.
  48 #
  49 #Returns:
  50 #
  51 #  Value shifted left identified by the Count.
  52 #
  53 #--*/
  54 ASM_PFX(LShiftU64):
  55
  56     movl   4(%esp), %eax # dword ptr Operand[0]
  57     movl   8(%esp), %edx # dword ptr Operand[4]
  58
  59     #
  60     # CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EAX is not touched
  61     # For CL of 32 - 63, it will be shifted 0 - 31 so we will move eax to edx later.
  62     #
  63     movl   0xC(%esp), %ecx # Count
  64     andl   $63, %ecx
  65     shld   %cl, %eax, %edx
  66     shlb   %cl, %eax
  67
  68     #
  69     # Since Count is 32 - 63, eax will have been shifted  by 0 - 31
  70     # If shifted by 32 or more, set lower 32 bits to zero.
  71     #
  72     cmpl   $32, %ecx
  73     jc     _LShiftU64_Done
  74
  75     movl   %eax, %edx
  76     xorl   %eax, %eax
  77
  78 _LShiftU64_Done:
  79
  80     ret
  81 #LShiftU64 ENDP
  82