@ *****************************************************************
@
@               The Compcert verified compiler
@
@           Xavier Leroy, INRIA Paris-Rocquencourt
@
@ Copyright (c) 2013 Institut National de Recherche en Informatique et
@  en Automatique.
@
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@ modification, are permitted provided that the following conditions are met:
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@       notice, this list of conditions and the following disclaimer.
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@       documentation and/or other materials provided with the distribution.
@     * Neither the name of the <organization> nor the
@       names of its contributors may be used to endorse or promote products
@       derived from this software without specific prior written permission.
@ 
@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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@ *********************************************************************

@ Helper functions for 64-bit integer arithmetic.  ARM version.

        .text

@@@ Shift right unsigned	

@ Note on ARM shifts: the shift amount is taken modulo 256.
@ If shift amount mod 256 >= 32, the shift produces 0.

@ Algorithm:
@    RL = (XL >> N) | (XH << (32-N) | (XH >> (N-32))
@    RH = XH >> N        
@ If N = 0:
@    RL = XL | 0 | 0
@    RH = XH
@ If 1 <= N <= 31:  1 <= 32-N <= 31  and  255 <= N-32 mod 256 <= 255
@    RL = (XL >> N) | (XH >> (32-N) | 0
@    RH = XH >> N        
@ If N = 32:
@    RL = 0 | XH | 0
@    RH = 0
@ If 33 <= N <= 63: 255 <= 32-N mod 256 <= 255 and 1 <= N-32 <= 31
@    RL = 0 | 0 | (XH >> (N-32))
@    RH = 0

	.global __i64_shr
__i64_shr:
        and r2, r2, #63         @ normalize amount to 0...63
        rsb r3, r2, #32         @ r3 = 32 - amount
        mov r0, r0, lsr r2
        orr r0, r0, r1, lsl r3
	sub r3, r2, #32         @ r3 = amount - 32
	orr r0, r0, r1, lsr r3
        mov r1, r1, lsr r2
        bx lr
	.type __i64_shr, %function
	.size __i64_shr, . - __i64_shr