[mirror_edk2.git] / EdkCompatibilityPkg / Foundation / Library / EfiCommonLib / Ia32 / RShiftU64.S

#/*++
#
#Copyright (c) 2006, 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.c
#
#Abstract:
#
#  64-bit right shift function for IA-32
#
#--*/
#
##include "Tiano.h"
#
#include "EfiBind.h"
#---------------------------------------------------------------------------
    .686: 
    #.MODEL flat,C
    .code: 

#---------------------------------------------------------------------------
.globl ASM_PFX(RShiftU64)
#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.
#
#--*/
ASM_PFX(RShiftU64):

    movl   4(%esp), %eax # dword ptr Operand[0]
    movl   8(%esp), %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. 
    #
    movl   0xC(%esp), %ecx  # Count
    andl   $63, %ecx
    shrd   %cl, %edx, %eax
    shrb   %cl, %edx

    cmpl   $32, %ecx
    jc     _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.
    #
    movl   %edx, %eax
    xorl   %edx, %edx

_RShiftU64_Done: 

    ret
#RShiftU64 ENDP
Commit	Line	Data
b962b6b5	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	# RShiftU64.c
	15	#
	16	#Abstract:
	17	#
	18	# 64-bit right shift function for IA-32
	19	#
	20	#--*/
	21	#
	22	##include "Tiano.h"
	23	#
	24	#include "EfiBind.h"
	25	#---------------------------------------------------------------------------
	26	.686:
	27	#.MODEL flat,C
	28	.code:
	29
	30	#---------------------------------------------------------------------------
	31	.globl ASM_PFX(RShiftU64)
	32	#UINT64
	33	#RShiftU64 (
	34	# IN UINT64 Operand,
	35	# IN UINTN Count
	36	# )
	37	#/*++
	38	#
	39	#Routine Description:
	40	# This routine allows a 64 bit value to be right shifted by 32 bits and returns the
	41	# shifted value.
	42	# Count is valid up 63. (Only Bits 0-5 is valid for Count)
	43	#Arguments:
	44	# Operand - Value to be shifted
	45	# Count - Number of times to shift right.
	46	#
	47	#Returns:
	48	#
	49	# Value shifted right identified by the Count.
	50	#
	51	#--*/
	52	ASM_PFX(RShiftU64):
	53
	54	movl 4(%esp), %eax # dword ptr Operand[0]
	55	movl 8(%esp), %edx # dword ptr Operand[4]
	56
	57	#
	58	# CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EDX is not touched
	59	# For CL of 32 - 63, it will be shifted 0 - 31 so we will move edx to eax later.
	60	#
	61	movl 0xC(%esp), %ecx # Count
	62	andl $63, %ecx
	63	shrd %cl, %edx, %eax
	64	shrb %cl, %edx
65
66	cmpl $32, %ecx
67	jc _RShiftU64_Done
68
69	#
70	# Since Count is 32 - 63, edx will have been shifted by 0 - 31
71	# If shifted by 32 or more, set upper 32 bits to zero.
72	#
73	movl %edx, %eax
74	xorl %edx, %edx
75
76	_RShiftU64_Done:
77
78	ret
79	#RShiftU64 ENDP
80