77 lines
2.5 KiB
C
77 lines
2.5 KiB
C
/*
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picoChip GCC support for 32-bit logical shift right.
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Copyright (C) 2003-2013 Free Software Foundation, Inc.
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Contributed by Picochip Ltd.
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Maintained by Daniel Towner (daniel.towner@picochip.com)
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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 int HItype __attribute__ ((mode (HI)));
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typedef unsigned int UHItype __attribute__ ((mode (HI)));
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typedef unsigned int USItype __attribute__ ((mode (SI)));
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typedef struct USIstruct {
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UHItype low, high;
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} USIstruct;
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typedef union USIunion {
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USItype l;
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USIstruct s;
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} USIunion;
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USItype __lshrsi3(USIunion value, HItype count) {
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USIunion result;
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int temp;
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/* Ignore a zero count until we get into the (count < 16)
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clause. This is slightly slower when shifting by zero, but faster
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and smaller in all other cases (due to the better scheduling
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opportunities available by putting the test near computational
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instructions. */
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if (count < 16) {
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/* Shift low and high words by the count. */
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result.s.low = value.s.low >> count;
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result.s.high = value.s.high >> count;
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/* There is now a hole in the upper `count' bits of the low
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word. Shift the lower `count' bits of the upper word into the
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low word. This only works when count isn't zero. */
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if (count != 0) {
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temp = value.s.high << (16 - count);
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result.s.low |= temp;
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}
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} else {
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/* Shift the upper word of the source into the lower word of the
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result, and zero the result's upper word. Note that we actually
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ned to shift by (count - 16), but as we are only using the
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bottom 4 bits, this is equivalent to shifting by count. */
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result.s.low = value.s.high >> count;
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result.s.high = 0;
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}
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return result.l;
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}
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