114 lines
3.6 KiB
C
114 lines
3.6 KiB
C
/*
|
|
|
|
picoChip GCC support for 32-bit arithmetic shift right.
|
|
|
|
Copyright (C) 2003-2013 Free Software Foundation, Inc.
|
|
Contributed by Picochip Ltd.
|
|
Maintained by Daniel Towner (daniel.towner@picochip.com)
|
|
|
|
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 int HItype __attribute__ ((mode (HI)));
|
|
typedef unsigned int UHItype __attribute__ ((mode (HI)));
|
|
typedef unsigned int USItype __attribute__ ((mode (SI)));
|
|
|
|
typedef struct USIstruct {
|
|
UHItype low, high;
|
|
} USIstruct;
|
|
|
|
typedef union USIunion {
|
|
USItype l;
|
|
USIstruct s;
|
|
} USIunion;
|
|
|
|
USItype __ashrsi3(USIunion value, HItype count) {
|
|
USIunion result;
|
|
int temp;
|
|
int wordOfSignBits;
|
|
|
|
/* Ignore a zero count until we get into the (count < 16)
|
|
clause. This is slightly slower when shifting by zero, but faster
|
|
and smaller in all other cases (due to the better scheduling
|
|
opportunities available by putting the test near computational
|
|
instructions. */
|
|
/* if (count == 0) return value.l; */
|
|
|
|
if (count < 16) {
|
|
/* Shift low and high words by the count. The high word must use
|
|
an arithmetic shift. There is no arithmetic shift-right by
|
|
variable, so synthesise it. */
|
|
int signWord;
|
|
int reverseCount;
|
|
|
|
/* Shift low and high parts by the count. The upper word now has
|
|
invalid signed bits. */
|
|
result.s.low = value.s.low >> count;
|
|
result.s.high = value.s.high >> count;
|
|
|
|
if (count != 0) {
|
|
|
|
reverseCount = 16 - count;
|
|
|
|
/* Given a word of sign bits, shift back left to create the
|
|
destination sign bits. */
|
|
wordOfSignBits = __builtin_asri(value.s.high, 15);
|
|
signWord = wordOfSignBits << reverseCount;
|
|
result.s.high |= signWord;
|
|
|
|
/* There is now a hole in the upper `count' bits of the low
|
|
word. Shift the lower `count' bits of the upper word into the
|
|
low word. */
|
|
temp = value.s.high << reverseCount;
|
|
result.s.low |= temp;
|
|
}
|
|
|
|
} else {
|
|
int signWord;
|
|
|
|
/* Shift is greater than one word, so top word will always be set
|
|
to sign bits, and bottom word will be shifted from top word. */
|
|
result.s.low = value.s.high >> count;
|
|
result.s.high = __builtin_asri(value.s.high, 15);
|
|
|
|
if (count != 16) {
|
|
|
|
/* Shift the upper word of the source into the lower word of the
|
|
result. Arithmetically shift the upper word as well, to retain
|
|
the sign. This shift must be synthesised, as no such shift
|
|
exists in the instruction set. */
|
|
int signWord;
|
|
|
|
|
|
/* Given a complete word of sign-bits, shift this back left to
|
|
create the destination sign bits. */
|
|
signWord = result.s.high << (16 - count);
|
|
// signWord = wordOfSignBits << (16 - count);
|
|
|
|
/* Insert the sign bits to the result's low word. */
|
|
result.s.low |= signWord;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return result.l;
|
|
|
|
}
|