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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - SIGFPE due to illegal FP optimization"
href="http://llvm.org/bugs/show_bug.cgi?id=17088">17088</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>SIGFPE due to illegal FP optimization
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>kcc@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre><this is fresh clang trunk r189814 on linux x86_64>
% cat fpe.cc
#include <fenv.h>
double zero = 0.0;
#define max(a, b) (a > b ? a : b)
int main() {
feenableexcept(FE_DIVBYZERO);
double z = 3.0 / max(1.0, zero);
return z == 3.0;
}
% clang fpe.cc -lm -g && ./a.out
% gcc fpe.cc -lm -g && ./a.out
% gcc -O1 fpe.cc -lm -g && ./a.out
% clang -O1 fpe.cc -lm -g && ./a.out
Floating point exception (core dumped)
% gdb ./a.out
Reading symbols from /home/kcc/tmp/./a.out...done.
(gdb) r
Starting program: /home/kcc/tmp/./a.out
Program received signal SIGFPE, Arithmetic exception.
0x000000000040057e in main () at fpe.cc:6
6 double z = 3.0 / max(1.0, zero);
(gdb) disassemble
Dump of assembler code for function main():
0x0000000000400560 <+0>: push %rax
0x0000000000400561 <+1>: mov $0x4,%edi
0x0000000000400566 <+6>: callq 0x400460 <feenableexcept@plt>
0x000000000040056b <+11>: movsd 0x12d(%rip),%xmm0 # 0x4006a0
0x0000000000400573 <+19>: movsd 0x200ab5(%rip),%xmm1 # 0x601030
<zero>
0x000000000040057b <+27>: movaps %xmm0,%xmm2
=> 0x000000000040057e <+30>: divsd %xmm1,%xmm2
0x0000000000400582 <+34>: movsd 0x11e(%rip),%xmm3 # 0x4006a8
0x000000000040058a <+42>: ucomisd %xmm1,%xmm3
0x000000000040058e <+46>: seta %al
0x0000000000400591 <+49>: ucomisd %xmm0,%xmm2
0x0000000000400595 <+53>: setnp %cl
0x0000000000400598 <+56>: sete %dl
0x000000000040059b <+59>: and %cl,%dl
0x000000000040059d <+61>: or %al,%dl
0x000000000040059f <+63>: movzbl %dl,%eax
0x00000000004005a2 <+66>: pop %rdx
0x00000000004005a3 <+67>: retq
End of assembler dump.
(gdb)</pre>
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