<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - strlen (s) == 0 not folded when return type is casted to unsigned"
href="https://llvm.org/bugs/show_bug.cgi?id=28833">28833</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>strlen (s) == 0 not folded when return type is casted to unsigned
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>3.6
</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>Transformation Utilities
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>prathamesh.kulkarni@linaro.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Hi,
For the following test-case, strlen (s) == 0 is not folded to *s == 0.
_Bool f2(const char *s)
{
unsigned len = __builtin_strlen (s);
return len == 0;
}
Assembly with clang -O2 -S:
.text
.file "test-2.c"
.globl f2
.align 16, 0x90
.type f2,@function
f2: # @f2
.cfi_startproc
# BB#0:
pushq %rax
.Ltmp0:
.cfi_def_cfa_offset 16
callq strlen
testl %eax, %eax
sete %al
popq %rdx
retq
.Ltmp1:
.size f2, .Ltmp1-f2
.cfi_endproc
.ident "Ubuntu clang version 3.6.2-1 (tags/RELEASE_362/final) (based
on LLVM 3.6.2)"
.section ".note.GNU-stack","",@progbits
However if type of len is changed from unsigned to unsigned long,
then the transform takes place.
Is there a reason why the transform is disabled if the return
value (unsigned long) is stored in a smaller type (unsigned) ?
Thanks,
Prathamesh</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>