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;   Copyright (C) 2011 Free Software Foundation, Inc.
;   Contributed by Red Hat.
; 
; This file is free software; you can redistribute it and/or modify it
; under the terms of the GNU General Public License as published by the
; Free Software Foundation; either version 3, or (at your option) any
; later version.
; 
; This file is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
; General Public License for more details.
; 
; Under Section 7 of GPL version 3, you are granted additional
; permissions described in the GCC Runtime Library Exception, version
; 3.1, as published by the Free Software Foundation.
;
; You should have received a copy of the GNU General Public License and
; a copy of the GCC Runtime Library Exception along with this program;
; see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
; <http://www.gnu.org/licenses/>.

r8      =       0xffef0
r16     =       0xffee8
r9      =       0xffef1
r17     =       0xffee9
r10     =       0xffef2
r18     =       0xffeea
r11     =       0xffef3
r19     =       0xffeeb
r12     =       0xffef4
r20     =       0xffeec
r13     =       0xffef5
r21     =       0xffeed
r14     =       0xffef6
r22     =       0xffeee
r15     =       0xffef7
r23     =       0xffeef
        
        .text
        .global ___lshrsi3
        .type   ___lshrsi3, @function
___lshrsi3:

        ;; input:
        ;; 
        ;; [zero]
        ;; [count]   <= $sp+8
        ;; [in MSB]
        ;; [in]
        ;; [in]
        ;; [in LSB]  <- $sp+4

        ;; output:
        ;; 
        ;; [r8..r11] result

        ;; registers:
        ;;
        ;; AX - temp for shift/rotate
        ;; B  - count

        mov     a, [sp+8]       ; A now contains the count

        cmp     a, #0x20
        bc      $.Lcount_is_normal

        ;; count is out of bounds, just return zero.
        movw    r8, #0
        movw    r10, #0
        ret

.Lcount_is_normal:
        cmp0    a
        bnz     $.Lcount_is_nonzero

        ;; count is zero, just copy IN to OUT
        movw    ax, [sp+4]
        movw    r8, ax
        movw    ax, [sp+6]
        movw    r10, ax
        ret

.Lcount_is_nonzero:
        mov     b, a            ; B now contains the count also
        bf      a.4, $.Lcount_lt_16

        ;; count >= 16, shift 16 at a time.
        movw    r10, #0
        movw    ax, [sp+6]
        movw    r8, ax
        mov     a, b
        and     a, #0x0f
        sknz
        ret

        mov     b, a            ; B now contains the remaining count
        inc     b
        br      $.Lloop_top

.Lcount_lt_16:  
        ;; count is nonzero.  Do one 
        movw    ax, [sp+6]
        shrw    ax,1
        movw    r10, ax
        mov     a, [sp+5]
        rorc    a,1
        mov     r9, a
        mov     a, [sp+4]
        rorc    a,1
        mov     r8, a

        ;; we did one shift above; do as many more as we need now.
.Lloop_top:     
        dec     b
        sknz
        ret

        movw    ax, r10
        shrw    ax,1
        movw    r10, ax
        mov     a, r9
        rorc    a,1
        mov     r9, a
        mov     a, r8
        rorc    a,1
        mov     r8, a

        br      $.Lloop_top

        .size   ___lshrsi3, .-___lshrsi3