http://llvm.org/bugs/show_bug.cgi?id=16521
Bug ID: 16521
Summary: code with volatile struct produces wrong result at -O3
on x86_64-linux-gnu
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following code produces incorrect result when compiled with the current
clang trunk at -O3 on x86_64-linux (in both 32-bit and 64-bit modes). This is a
regression as both clang 3.2 and 3.3 produce correct code.
$ clang-trunk -v
clang version 3.4 (trunk 185306)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -O2 reduced.c
$ a.out
0
$ clang-trunk -O3 reduced.c
$ a.out
1
$ clang-3.3 -O3 reduced.c
$ a.out
0
$ clang-3.2 -O3 reduced.c
$ a.out
0
------------------------------------
int printf (const char *, ...);
int a, b, c, d, e = 1;
struct S
{
int f;
};
volatile struct S s;
void foo (int *p)
{
int i;
for (i = 0; i < 4; i++) {
int t[2] = {0, 0};
for (; b < 2; b++) {
d = 0;
for (; d >= 0; d--)
c = 0;
for (; c < 7; c++)
t[1] ^= 1;
}
if (t[1]) {
s;
*p = e;
}
}
}
int main ()
{
foo (&a);
printf ("%d\n", a);
return 0;
}
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