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Diffstat (limited to 'config/picochip/libgccExtras/ashrsi3.c')
-rw-r--r-- | config/picochip/libgccExtras/ashrsi3.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/config/picochip/libgccExtras/ashrsi3.c b/config/picochip/libgccExtras/ashrsi3.c new file mode 100644 index 0000000..fee3342 --- /dev/null +++ b/config/picochip/libgccExtras/ashrsi3.c @@ -0,0 +1,118 @@ +/* + +picoChip GCC support for 32-bit arithmetic shift right. + +Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc. +Contributed by picoChip Designs 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 2, or (at your option) any +later version. + +In addition to the permissions in the GNU General Public License, the +Free Software Foundation gives you unlimited permission to link the +compiled version of this file into combinations with other programs, +and to distribute those combinations without any restriction coming +from the use of this file. (The General Public License restrictions +do apply in other respects; for example, they cover modification of +the file, and distribution when not linked into a combine +executable.) + +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. + +You should have received a copy of the GNU General Public License +along with this program; see the file COPYING. If not, write to +the Free Software Foundation, 51 Franklin Street, Fifth Floor, +Boston, MA 02110-1301, USA. */ + +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; + +} |