121 lines
2.7 KiB
C
121 lines
2.7 KiB
C
/* Generic signed 32 bit division implementation.
|
|
Copyright (C) 2009-2014 Free Software Foundation, Inc.
|
|
Contributed by Embecosm on behalf of Adapteva, Inc.
|
|
|
|
This file is part of GCC.
|
|
|
|
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/>. */
|
|
|
|
typedef union { unsigned int i; float f; } fu;
|
|
|
|
/* Although the semantics of the function ask for signed / unsigned inputs,
|
|
for the actual implementation we use unsigned numbers. */
|
|
unsigned int __divsi3 (unsigned int a, unsigned int b);
|
|
|
|
unsigned int
|
|
__divsi3 (unsigned int a, unsigned int b)
|
|
{
|
|
unsigned int sign = (int) (a ^ b) >> 31;
|
|
unsigned int d, t, s0, s1, s2, r0, r1;
|
|
fu u0, u1, u2, u1b, u2b;
|
|
|
|
a = abs (a);
|
|
b = abs (b);
|
|
|
|
if (b > a)
|
|
return 0;
|
|
|
|
/* Compute difference in number of bits in S0. */
|
|
u0.i = 0x40000000;
|
|
u1b.i = u2b.i = u0.i;
|
|
u1.i = a;
|
|
u2.i = b;
|
|
u1.i = a | u0.i;
|
|
t = 0x4b800000 | ((a >> 23) & 0xffff);
|
|
if (a >> 23)
|
|
{
|
|
u1.i = t;
|
|
u1b.i = 0x4b800000;
|
|
}
|
|
u2.i = b | u0.i;
|
|
t = 0x4b800000 | ((b >> 23) & 0xffff);
|
|
if (b >> 23)
|
|
{
|
|
u2.i = t;
|
|
u2b.i = 0x4b800000;
|
|
}
|
|
u1.f = u1.f - u1b.f;
|
|
u2.f = u2.f - u2b.f;
|
|
s1 = u1.i >> 23;
|
|
s2 = u2.i >> 23;
|
|
s0 = s1 - s2;
|
|
|
|
b <<= s0;
|
|
d = b - 1;
|
|
|
|
r0 = 1 << s0;
|
|
r1 = 0;
|
|
t = a - b;
|
|
if (t <= a)
|
|
{
|
|
a = t;
|
|
r1 = r0;
|
|
}
|
|
|
|
#define STEP(n) case n: a += a; t = a - d; if (t <= a) a = t;
|
|
switch (s0)
|
|
{
|
|
STEP (31)
|
|
STEP (30)
|
|
STEP (29)
|
|
STEP (28)
|
|
STEP (27)
|
|
STEP (26)
|
|
STEP (25)
|
|
STEP (24)
|
|
STEP (23)
|
|
STEP (22)
|
|
STEP (21)
|
|
STEP (20)
|
|
STEP (19)
|
|
STEP (18)
|
|
STEP (17)
|
|
STEP (16)
|
|
STEP (15)
|
|
STEP (14)
|
|
STEP (13)
|
|
STEP (12)
|
|
STEP (11)
|
|
STEP (10)
|
|
STEP (9)
|
|
STEP (8)
|
|
STEP (7)
|
|
STEP (6)
|
|
STEP (5)
|
|
STEP (4)
|
|
STEP (3)
|
|
STEP (2)
|
|
STEP (1)
|
|
case 0: ;
|
|
}
|
|
r0 = r1 | (r0-1 & a);
|
|
return (r0 ^ sign) - sign;
|
|
}
|