@ *****************************************************************
@
@               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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@ *********************************************************************

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

#include "sysdeps.h"

@@@ Auxiliary function for division and modulus. Don't call from C

@ On entry:  N = (r0, r1) numerator    D = (r2, r3) divisor	
@ On exit:   Q = (r4, r5) quotient     R = (r0, r1) remainder	
@ Locals:    M = (r6, r7) mask         TMP = r8 temporary	
	
FUNCTION(__i64_udivmod)
        orrs r8, r2, r3         @ is D == 0?
	it eq
        bxeq lr                 @ if so, return with unspecified results
        MOV r4, #0              @ Q = 0
        MOV r5, #0
        MOV r6, #1              @ M = 1
        MOV r7, #0
1:      cmp r3, #0              @ while ((signed) D >= 0) ...
        blt 2f
        subs r8, r0, r2         @ ... and N >= D ...
        sbcs r8, r1, r3
        blo 2f
        adds r2, r2, r2         @ D = D << 1
        adc r3, r3, r3
        adds r6, r6, r6         @ M = M << 1
        adc r7, r7, r7
        b 1b
2:      subs r0, r0, r2         @ N = N - D
        sbcs r1, r1, r3
        orr r4, r4, r6          @ Q = Q | M
        orr r5, r5, r7
        bhs 3f                  @ if N was >= D, continue
        adds r0, r0, r2         @ otherwise, undo what we just did
        adc r1, r1, r3          @ N = N + D
        bic r4, r4, r6          @ Q = Q & ~M
        bic r5, r5, r7
3:      lsrs r7, r7, #1         @ M = M >> 1
        rrx r6, r6
        lsrs r3, r3, #1         @ D = D >> 1
        rrx r2, r2
        orrs r8, r6, r7         @ repeat while (M != 0) ...
        bne 2b
        bx lr
ENDFUNCTION(__i64_udivmod)