[llvm-bugs] [Bug 25629] New: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu (in 32-bit mode)
via llvm-bugs
llvm-bugs at lists.llvm.org
Tue Nov 24 12:33:34 PST 2015
https://llvm.org/bugs/show_bug.cgi?id=25629
Bug ID: 25629
Summary: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu (in
32-bit mode)
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangbugs at nondot.org
Reporter: su at cs.ucdavis.edu
CC: llvm-bugs at lists.llvm.org
Classification: Unclassified
The following code is miscompiled by the current clang trunk on
x86_64-linux-gnu at -O1, -O2 and -O3 in 32-bit mode (but not in 64-bit mode).
This is a regression from 3.7.x.
$ clang-trunk -v
clang version 3.8.0 (trunk 253909)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/tools/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.1.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4
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/5.1.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ clang-trunk -m32 -O0 small.c; ./a.out
48
$ clang-trunk -m64 -O1 small.c; ./a.out
48
$ clang-trunk -m32 -Os small.c; ./a.out
48
$ clang-3.7.0 -m32 -O1 small.c; ./a.out
48
$
$
$
$ clang-trunk -m32 -O1 small.c
$ ./a.out
49
$
-----------------------------------
int printf (const char *, ...);
int a, d;
static char b = 48, c;
int
main ()
{
c = b;
for (; c < 45; c++)
a = a ? d : d < a;
b = 0;
printf ("%d\n", c);
return 0;
}
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