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

   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 #include "Tiano.h"
  23
  24 UINT64
  25 LShiftU64 (
  26   IN UINT64   Operand,
  27   IN UINTN    Count
  28   )
  29 /*++
  30
  31 Routine Description:
  32
  33   This routine allows a 64 bit value to be left shifted by 32 bits and
  34   returns the shifted value.
  35   Count is valid up 63. (Only Bits 0-5 is valid for Count)
  36
  37 Arguments:
  38
  39   Operand - Value to be shifted
  40   Count   - Number of times to shift left.
  41
  42 Returns:
  43
  44   Value shifted left identified by the Count.
  45
  46 --*/
  47 {
  48   __asm {
  49
  50     mov    eax, dword ptr Operand[0]
  51     mov    edx, dword ptr Operand[4]
  52
  53     ;
  54     ; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EAX is not touched
  55     ; For CL of 32 - 63, it will be shifted 0 - 31 so we will move eax to edx later.
  56     ;
  57     mov    ecx, Count
  58     and    ecx, 63
  59     shld   edx, eax, cl
  60     shl    eax, cl
  61
  62     ;
  63     ; Since Count is 32 - 63, eax will have been shifted  by 0 - 31
  64     ; If shifted by 32 or more, set lower 32 bits to zero.
  65     ;
  66     cmp    ecx, 32
  67     jc     short _LShiftU64_Done
  68
  69     mov    edx, eax
  70     xor    eax, eax
  71
  72 _LShiftU64_Done:
  73   }
  74 }