1 files changed, 86 insertions, 0 deletions
diff --git a/EDK/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.asm b/EDK/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.asm
new file mode 100644
index 0000000..de05d20
--- /dev/null
+++ b/EDK/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.asm
@@ -0,0 +1,86 @@
+      TITLE   RShiftU64.asm: 64-bit right shift function for IA-32
+
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2004, Intel Corporation                                                         
+; All rights reserved. This program and the accompanying materials                          
+; are licensed and made available under the terms and conditions of the BSD License         
+; which accompanies this distribution.  The full text of the license may be found at        
+; http://opensource.org/licenses/bsd-license.php                                            
+;                                                                                           
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             
+; 
+; Module Name:
+;
+;   RShiftU64.asm
+; 
+; Abstract:
+; 
+;   64-bit right shift function for IA-32
+;
+;------------------------------------------------------------------------------
+
+  .686P
+  .XMM
+  .MODEL SMALL
+  .CODE
+
+RShiftU64 PROTO C  Operand: QWORD, Count: DWORD
+
+RShiftU64 PROC C   Operand: QWORD, Count: DWORD
+
+;------------------------------------------------------------------------------
+; UINT64
+; RShiftU64 (
+;    IN UINT64   Operand,
+;    IN UINTN    Count
+;    )
+;
+; Routine Description:
+;
+;   This routine allows a 64 bit value to be right shifted by 32 bits and returns the 
+;   shifted value.
+;   Count is valid up 63. (Only Bits 0-5 is valid for Count)
+;
+; Arguments:
+;
+;   Operand - Value to be shifted
+;   Count   - Number of times to shift right.
+;  
+; Returns:
+;
+;   Value shifted right identified by the Count.
+;------------------------------------------------------------------------------  
+
+  push   ecx
+  
+  mov    eax, dword ptr Operand[0]
+  mov    edx, dword ptr Operand[4]
+  
+  ;
+  ; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EDX is not touched
+  ; For CL of 32 - 63, it will be shifted 0 - 31 so we will move edx to eax later. 
+  ;
+  mov    ecx, Count
+  and    ecx, 63
+  shrd   eax, edx, cl
+  shr    edx, cl
+
+  cmp    ecx, 32
+  jc     short _RShiftU64_Done
+
+  ;
+  ; Since Count is 32 - 63, edx will have been shifted  by 0 - 31                                                     
+  ; If shifted by 32 or more, set upper 32 bits to zero.
+  ;
+  mov    eax, edx
+  xor    edx, edx
+
+_RShiftU64_Done:
+  pop    ecx
+  ret
+
+RShiftU64 ENDP
+
+END