StdLib/LibC/CRT/Ia32/llshr.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) 2009 - 2011, Intel Corporation. All rights reserved.<BR>
   7   This program and the accompanying materials are licensed and made available
   8   under the terms and conditions of the BSD License which accompanies this
   9   distribution.  The full text of the license may be found at
  10   http://opensource.org/licenses/bsd-license.php.
  11
  12   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  13   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14
  15 **/
  16
  17
  18 /*
  19  * Shifts a 64-bit signed value right by a particular number of bits.
  20  */
  21 __declspec(naked) void __cdecl _allshr (void)
  22 {
  23   _asm {
  24     ;
  25     ; Handle shifts of 64 bits or more (if shifting 64 bits or more, the result
  26     ; depends only on the high order bit of edx).
  27       ;
  28     cmp     cl,64
  29     jae     short SIGNRETURN
  30
  31     ;
  32     ; Handle shifts of between 0 and 31 bits
  33     ;
  34     cmp     cl, 32
  35     jae     short MORE32
  36     shrd    eax,edx,cl
  37     sar     edx,cl
  38     ret
  39
  40     ;
  41     ; Handle shifts of between 32 and 63 bits
  42     ;
  43 MORE32:
  44     mov     eax,edx
  45     sar     edx,31
  46     and     cl,31
  47     sar     eax,cl
  48     ret
  49
  50     ;
  51     ; Return double precision 0 or -1, depending on the sign of edx
  52     ;
  53 SIGNRETURN:
  54     sar     edx,31
  55     mov     eax,edx
  56     ret
  57   }
  58 }