https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111290
Bug ID: 111290
Summary: [11/12/13/14 Regression] Wrong code at -O0 on
x86_64-pc-linux-gnu
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: jwzeng at nuaa dot edu.cn
Target Milestone: ---
Compiler Explorer: https://godbolt.org/z/Ee3fMoqPr
The following code snippet, gcc at -O0 produces the wrong code. I tested it on
other versions of gcc and found that this bug was introduced starting from
`gcc-4.9.0`.
$ cat test.c
#include <stdint.h>
int printf(const char *, ...);
volatile uint16_t a = (unsigned short)27267;
volatile int32_t b = 191725925;
volatile int32_t c = 633417204;
volatile uint64_t d = 6049561019410052129ULL;
volatile int32_t e = 2024295172;
volatile int8_t res = (signed char)108;
int main()
{
b = (c |= d / a) >= ((e %= 0x6B1D8456) > (res ^= c));
printf("%d\n", res);
}
$
$ gcc-tk test.c; ./a.out
-104
$ gcc-4.9.0 test.c; ./a.out
-104
$ gcc-4.8.5 test.c; ./a.out
-112
$ clang-tk test.c; ./a.out
-112
$ ccomp test.c; ./a.out
-112
$
$ gcc-tk --version
gcc (GCC) 14.0.0 20230829 (experimental) [master r14-3534-gebffc840f5]
Copyright (C) 2023 Free Software Foundation, Inc.
$
$ gcc-4.9.0 --version
gcc (GCC) 4.9.0
Copyright (C) 2014 Free Software Foundation, Inc.
$
$ gcc-4.8.5 --version
gcc (GCC) 4.8.5
Copyright (C) 2015 Free Software Foundation, Inc.
$
$ clang-tk --version
Ubuntu clang version 18.0.0
(++20230821052626+634b2fd2cac2-1~exp1~20230821172748.738)
Target: x86_64-pc-linux-gnu
$
$ ccomp --version
The CompCert C verified compiler, version 3.12
