@ *****************************************************************
@
@               The Compcert verified compiler
@
@           Xavier Leroy, INRIA Paris-Rocquencourt
@
@ Copyright (c) 2013 Institut National de Recherche en Informatique et
@  en Automatique.
@
@ Redistribution and use in source and binary forms, with or without
@ modification, are permitted provided that the following conditions are met:
@     * Redistributions of source code must retain the above copyright
@       notice, this list of conditions and the following disclaimer.
@     * Redistributions in binary form must reproduce the above copyright
@       notice, this list of conditions and the following disclaimer in the
@       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
@ "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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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(__compcert_i64_udivmod)
        orrs r8, Reg1LO, Reg1HI         @ is D == 0?
        it eq
        bxeq lr                         @ if so, return with unspecified results
        MOV Reg2LO, #0                  @ Q = 0
        MOV Reg2HI, #0
        MOV Reg3LO, #1                  @ M = 1
        MOV Reg3HI, #0
1:      cmp Reg1HI, #0                  @ while ((signed) D >= 0) ...
        blt 2f
        subs r8, Reg0LO, Reg1LO         @ ... and N >= D ...
        sbcs r8, Reg0HI, Reg1HI
        blo 2f
        adds Reg1LO, Reg1LO, Reg1LO     @ D = D << 1
        adc Reg1HI, Reg1HI, Reg1HI
        adds Reg3LO, Reg3LO, Reg3LO     @ M = M << 1
        adc Reg3HI, Reg3HI, Reg3HI
        b 1b
2:      subs Reg0LO, Reg0LO, Reg1LO     @ N = N - D
        sbcs Reg0HI, Reg0HI, Reg1HI
        orr Reg2LO, Reg2LO, Reg3LO      @ Q = Q | M
        orr Reg2HI, Reg2HI, Reg3HI
        bhs 3f                          @ if N was >= D, continue
        adds Reg0LO, Reg0LO, Reg1LO     @ otherwise, undo what we just did
        adc Reg0HI, Reg0HI, Reg1HI      @ N = N + D
        bic Reg2LO, Reg2LO, Reg3LO      @ Q = Q & ~M
        bic Reg2HI, Reg2HI, Reg3HI
3:      lsrs Reg3HI, Reg3HI, #1         @ M = M >> 1
        rrx Reg3LO, Reg3LO
        lsrs Reg1HI, Reg1HI, #1         @ D = D >> 1
        rrx Reg1LO, Reg1LO
        orrs r8, Reg3LO, Reg3HI         @ repeat while (M != 0) ...
        bne 2b
        bx lr
ENDFUNCTION(__compcert_i64_udivmod)