1//===-- int_mulv_impl.inc - Implement __mulv[sdt]i3 ---------------*- 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-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Helper used by __mulvsi3, __mulvdi3 and __mulvti3.
10//
11//===----------------------------------------------------------------------===//
12
13#include "int_lib.h"
14
15// Returns: a * b
16
17// Effects: aborts if a * b overflows
18
19static __inline fixint_t __mulvXi3(fixint_t a, fixint_t b) {
20  const int N = (int)(sizeof(fixint_t) * CHAR_BIT);
21  const fixint_t MIN = (fixint_t)1 << (N - 1);
22  const fixint_t MAX = ~MIN;
23  if (a == MIN) {
24    if (b == 0 || b == 1)
25      return a * b;
26    compilerrt_abort();
27  }
28  if (b == MIN) {
29    if (a == 0 || a == 1)
30      return a * b;
31    compilerrt_abort();
32  }
33  fixint_t sa = a >> (N - 1);
34  fixint_t abs_a = (a ^ sa) - sa;
35  fixint_t sb = b >> (N - 1);
36  fixint_t abs_b = (b ^ sb) - sb;
37  if (abs_a < 2 || abs_b < 2)
38    return a * b;
39  if (sa == sb) {
40    if (abs_a > MAX / abs_b)
41      compilerrt_abort();
42  } else {
43    if (abs_a > MIN / -abs_b)
44      compilerrt_abort();
45  }
46  return a * b;
47}
48