| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| #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 |
