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1//===-- int_mulo_impl.inc - Implement __mulo[sdt]i4 ---------------*- C -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Helper used by __mulosi4, __mulodi4 and __muloti4.10//11//===----------------------------------------------------------------------===//12 13#include "int_lib.h"14 15// Returns: a * b16 17// Effects: sets *overflow to 1 if a * b overflows18 19static __inline fixint_t __muloXi4(fixint_t a, fixint_t b, int *overflow) {20 const int N = (int)(sizeof(fixint_t) * CHAR_BIT);21 const fixint_t MIN = (fixint_t)((fixuint_t)1 << (N - 1));22 const fixint_t MAX = ~MIN;23 *overflow = 0;24 fixint_t result = (fixuint_t)a * b;25 if (a == MIN) {26 if (b != 0 && b != 1)27 *overflow = 1;28 return result;29 }30 if (b == MIN) {31 if (a != 0 && a != 1)32 *overflow = 1;33 return result;34 }35 fixint_t sa = a >> (N - 1);36 fixint_t abs_a = (a ^ sa) - sa;37 fixint_t sb = b >> (N - 1);38 fixint_t abs_b = (b ^ sb) - sb;39 if (abs_a < 2 || abs_b < 2)40 return result;41 if (sa == sb) {42 if (abs_a > MAX / abs_b)43 *overflow = 1;44 } else {45 if (abs_a > MIN / -abs_b)46 *overflow = 1;47 }48 return result;49}50