https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67857
Bug ID: 67857
Summary: noreturn + volatile results in wrong code
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: karl at skomski dot com
Target Milestone: ---
On Linux/x86-64, GCC 5.2 (g++ -m32 -O1) optimizes this test into wrong code:
Important is the volatile argument to Increment and __noreturn__ function in
the if clause.
```
#include <stdlib.h>
#include <stdio.h>
int Increment(volatile int* ptr, int increment) { // volatile
int temp = *ptr;
*ptr += increment;
return temp + increment;
}
int main() {
// Test at rollover boundary between int_max and int_min.
int test_val = 1 << (sizeof(int) * 8 - 1);
int value = -1 ^ test_val;
int new_value = Increment(&value, 1);
if (test_val != value) exit(100);
if (value != new_value) exit(200);
return 0;
}
```
produces
```
Fatal 200
[1] 3789 exit 200
```
```
.cfi_startproc
lea ecx, [esp+4]
.cfi_def_cfa 1, 0
and esp, -16
push DWORD PTR [ecx-4]
push ebp
.cfi_escape 0x10,0x5,0x2,0x75,0
mov ebp, esp
push ecx
.cfi_escape 0xf,0x3,0x75,0x7c,0x6
sub esp, 20
mov DWORD PTR [ebp-12], 2147483647
mov eax, DWORD PTR [ebp-12]
mov eax, DWORD PTR [ebp-12]
add eax, 1
mov DWORD PTR [ebp-12], eax
cmp DWORD PTR [ebp-12], -2147483648
je .L4
sub esp, 12
push 100
call exit
.L4:
sub esp, 12
push 200
call exit
.cfi_endproc
```
