| /* |
| |
| picoChip GCC support for 32-bit arithmetic shift right. |
| |
| Copyright (C) 2003-2014 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; |
| |
| } |