121 lines
2.7 KiB
C
121 lines
2.7 KiB
C
/* Generic signed 32 bit division implementation.
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Copyright (C) 2009-2019 Free Software Foundation, Inc.
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Contributed by Embecosm on behalf of Adapteva, Inc.
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This file is part of GCC.
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This file is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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This file is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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typedef union { unsigned int i; float f; } fu;
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/* Although the semantics of the function ask for signed / unsigned inputs,
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for the actual implementation we use unsigned numbers. */
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unsigned int __divsi3 (unsigned int a, unsigned int b);
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unsigned int
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__divsi3 (unsigned int a, unsigned int b)
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{
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unsigned int sign = (int) (a ^ b) >> 31;
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unsigned int d, t, s0, s1, s2, r0, r1;
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fu u0, u1, u2, u1b, u2b;
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a = abs (a);
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b = abs (b);
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if (b > a)
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return 0;
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/* Compute difference in number of bits in S0. */
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u0.i = 0x40000000;
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u1b.i = u2b.i = u0.i;
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u1.i = a;
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u2.i = b;
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u1.i = a | u0.i;
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t = 0x4b800000 | ((a >> 23) & 0xffff);
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if (a >> 23)
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{
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u1.i = t;
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u1b.i = 0x4b800000;
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}
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u2.i = b | u0.i;
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t = 0x4b800000 | ((b >> 23) & 0xffff);
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if (b >> 23)
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{
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u2.i = t;
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u2b.i = 0x4b800000;
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}
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u1.f = u1.f - u1b.f;
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u2.f = u2.f - u2b.f;
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s1 = u1.i >> 23;
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s2 = u2.i >> 23;
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s0 = s1 - s2;
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b <<= s0;
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d = b - 1;
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r0 = 1 << s0;
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r1 = 0;
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t = a - b;
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if (t <= a)
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{
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a = t;
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r1 = r0;
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}
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#define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t;
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switch (s0)
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{
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STEP (31)
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STEP (30)
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STEP (29)
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STEP (28)
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STEP (27)
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STEP (26)
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STEP (25)
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STEP (24)
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STEP (23)
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STEP (22)
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STEP (21)
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STEP (20)
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STEP (19)
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STEP (18)
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STEP (17)
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STEP (16)
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STEP (15)
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STEP (14)
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STEP (13)
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STEP (12)
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STEP (11)
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STEP (10)
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STEP (9)
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STEP (8)
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STEP (7)
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STEP (6)
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STEP (5)
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STEP (4)
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STEP (3)
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STEP (2)
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STEP (1)
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case 0: ;
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}
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r0 = r1 | (r0-1 & a);
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return (r0 ^ sign) - sign;
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}
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