CryptoPkg/Library/IntrinsicLib/Ia32/MathLlshr.asm

   1 ;***
   2 ;llshr.asm - long shift right
   3 ;
   4 ;       Copyright (c) Microsoft Corporation. All rights reserved.
   5 ;       SPDX-License-Identifier: BSD-2-Clause-Patent
   6 ;
   7 ;Purpose:
   8 ;       define signed long shift right routine
   9 ;           __allshr
  10 ;
  11 ;Original Implemenation: MSVC 14.12.25827
  12 ;
  13 ;*******************************************************************************
  14     .686
  15     .model  flat,C
  16     .code
  17
  18
  19
  20 ;***
  21 ;llshr - long shift right
  22 ;
  23 ;Purpose:
  24 ;       Does a signed Long Shift Right
  25 ;       Shifts a long right any number of bits.
  26 ;
  27 ;Entry:
  28 ;       EDX:EAX - long value to be shifted
  29 ;       CL    - number of bits to shift by
  30 ;
  31 ;Exit:
  32 ;       EDX:EAX - shifted value
  33 ;
  34 ;Uses:
  35 ;       CL is destroyed.
  36 ;
  37 ;Exceptions:
  38 ;
  39 ;*******************************************************************************
  40 _allshr PROC NEAR
  41
  42 ;
  43 ; Handle shifts of 64 bits or more (if shifting 64 bits or more, the result
  44 ; depends only on the high order bit of edx).
  45 ;
  46         cmp     cl,64
  47         jae     short RETSIGN
  48
  49 ;
  50 ; Handle shifts of between 0 and 31 bits
  51 ;
  52         cmp     cl, 32
  53         jae     short MORE32
  54         shrd    eax,edx,cl
  55         sar     edx,cl
  56         ret
  57
  58 ;
  59 ; Handle shifts of between 32 and 63 bits
  60 ;
  61 MORE32:
  62         mov     eax,edx
  63         sar     edx,31
  64         and     cl,31
  65         sar     eax,cl
  66         ret
  67
  68 ;
  69 ; Return double precision 0 or -1, depending on the sign of edx
  70 ;
  71 RETSIGN:
  72         sar     edx,31
  73         mov     eax,edx
  74         ret
  75
  76 _allshr ENDP
  77
  78         end