/* * Copyright (c) 2012, Google Inc. All rights reserved. * Copyright (C) 2014 Apple Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following disclaimer * in the documentation and/or other materials provided with the * distribution. * * Neither the name of Google Inc. nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #ifndef SaturatedArithmetic_h #define SaturatedArithmetic_h #include "Compiler.h" #include <limits> #include <stdint.h> #include <stdlib.h> inline bool signedAddOverflows(int32_t a, int32_t b, int32_t& result) { #if COMPILER_HAS_CLANG_BUILTIN(__builtin_sadd_overflow) && !(defined __clang_major__ && __clang_major__ < 7) return __builtin_sadd_overflow(a, b, &result); #else uint32_t ua = a; uint32_t ub = b; uint32_t uresult = ua + ub; result = static_cast<int32_t>(uresult); // Can only overflow if the signed bit of the two values match. If the signed // bit of the result and one of the values differ it did overflow. return !((ua ^ ub) >> 31) && (uresult ^ ua) >> 31; #endif } inline int32_t saturatedAddition(int32_t a, int32_t b) { int32_t result; #if CPU(ARM_THUMB2) asm("qadd %[sum], %[addend], %[augend]" : [sum]"=r"(result) : [augend]"r"(a), [addend]"r"(b) : /* Nothing is clobbered. */ ); #else if (signedAddOverflows(a, b, result)) result = std::numeric_limits<int32_t>::max() + (static_cast<uint32_t>(a) >> 31); #endif return result; } inline bool signedSubtractOverflows(int32_t a, int32_t b, int32_t& result) { #if COMPILER_HAS_CLANG_BUILTIN(__builtin_ssub_overflow) && !(defined __clang_major__ && __clang_major__ < 7) return __builtin_ssub_overflow(a, b, &result); #else uint32_t ua = a; uint32_t ub = b; uint32_t uresult = ua - ub; result = static_cast<int32_t>(uresult); // Can only overflow if the signed bit of the two values do not match. If the // signed bit of the result and the first value differ it did overflow. return (ua ^ ub) >> 31 && (uresult ^ ua) >> 31; #endif } inline int32_t saturatedSubtraction(int32_t a, int32_t b) { int32_t result; #if CPU(ARM_THUMB2) asm("qsub %[difference], %[minuend], %[subtrahend]" : [difference]"=r"(result) : [minuend]"r"(a), [subtrahend]"r"(b) : /* Nothing is clobbered. */ ); #else if (signedSubtractOverflows(a, b, result)) result = std::numeric_limits<int32_t>::max() + (static_cast<uint32_t>(a) >> 31); #endif return result; } #endif // SaturatedArithmetic_h