http://llvm.org/bugs/show_bug.cgi?id=15920
Bug ID: 15920
Summary: clang -O3 and loops result in garbage value
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The testcase below produces random output when compiled at -O3 with current
clang trunk (-O2 or below is fine). Perhaps a bad interaction with the loop
optimizer?
$ clang -v
clang version 3.3 (trunk 181189)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang -O2 test.c
$ ./a.out
1
$ clang -O3 test.c
$ ./a.out
2130055448
$
---------------------------
int printf(const char *, ...);
signed char c, d;
int i;
int
main ()
{
for (c = 0; c > -16; --c)
{
int *j = &i;
*j = 1;
for (d = 0; d; d = d + 0)
*j = 0;
}
printf ("%d\n", i);
return 0;
}
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