| /* |
| * 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 |