1#include <cstdint>
2#include <mutex>
3#include <thread>
4
5std::mutex t1_mutex, t2_mutex;
6
7struct test_data {
8 uint32_t eax;
9 uint32_t ebx;
10
11 struct alignas(16) {
12 uint64_t mantissa;
13 uint16_t sign_exp;
14 } st0;
15};
16
17void t_func(std::mutex &t_mutex, const test_data &t_data) {
18 std::lock_guard<std::mutex> t_lock(t_mutex);
19
20 asm volatile(
21 "finit\t\n"
22 "fldt %2\t\n"
23 "int3\n\t"
24 :
25 : "a"(t_data.eax), "b"(t_data.ebx), "m"(t_data.st0)
26 : "st"
27 );
28}
29
30int main() {
31 test_data t1_data = {
32 .eax = 0x05060708,
33 .ebx = 0x15161718,
34 .st0 = {.mantissa: 0x8070605040302010, .sign_exp: 0x4000},
35 };
36 test_data t2_data = {
37 .eax = 0x25262728,
38 .ebx = 0x35363738,
39 .st0 = {.mantissa: 0x8171615141312111, .sign_exp: 0xc000},
40 };
41
42 // block both threads from proceeding
43 std::unique_lock<std::mutex> m1_lock(t1_mutex);
44 std::unique_lock<std::mutex> m2_lock(t2_mutex);
45
46 // start both threads
47 std::thread t1(t_func, std::ref(t&: t1_mutex), std::ref(t&: t1_data));
48 std::thread t2(t_func, std::ref(t&: t2_mutex), std::ref(t&: t2_data));
49
50 // release lock on thread 1 to make it interrupt the program
51 m1_lock.unlock();
52 // wait for thread 1 to finish
53 t1.join();
54
55 // release lock on thread 2
56 m2_lock.unlock();
57 // wait for thread 2 to finish
58 t2.join();
59
60 return 0;
61}
62

source code of lldb/test/Shell/Register/Inputs/x86-multithread-read.cpp