https://llvm.org/bugs/show_bug.cgi?id=26994
Bug ID: 26994
Summary: wrong code at -O1 and above in 32-bit mode on
x86_64-linux-gnu
Product: clang
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangbugs at nondot.org
Reporter: chengniansun at gmail.com
CC: llvm-bugs at lists.llvm.org
Classification: Unclassified
The following code is miscompiled by the trunk at -O1 and above in 32-bit mode
on x86_64-linux-gnu.
This bug also affects clang-3.7 and later versions.
$: clang-trunk -v
clang version 3.9.0 (trunk 263789)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$:
$: clang-trunk small.c -O3 -m32 ; ./a.out ; echo $?
1
$: clang-trunk small.c -O1 -m32 ; ./a.out ; echo $?
1
$: clang-trunk small.c -O0 -m32 ; ./a.out ; echo $?
0
$: clang-3.7 small.c -O1 -m32 ; ./a.out ; echo $?
1
$: cat small.c
int main () {
int *p = 0;
trick:
if (p)
return *p;
int x = 0;
p = &x;
goto trick;
return 0;
}
$:
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