<html>
<head>
<base href="https://bugs.llvm.org/">
</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 - Missing constant propagation with "const" functions, works with "pure" functions"
href="https://bugs.llvm.org/show_bug.cgi?id=51962">51962</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing constant propagation with "const" functions, works with "pure" functions
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>int c;
__attribute__((noinline, pure)) int *pure_test(int *b) {
return *b && c ? &c : 0;
}
__attribute__((noinline, const)) int *const_test(int *b) { return b ? &c : 0; }
void escape(int *);
int test_pure() {
int a = 42;
escape(pure_test(&a));
return a; // OK, LLVM: mov eax, 42
}
int test_const() {
int a = 42;
escape(const_test(&a));
return a; // LLVM: mov eax, dword ptr [rsp + 4], GCC can optimize it to mov
eax, 42
}
<a href="https://godbolt.org/z/PKEKeEhM4">https://godbolt.org/z/PKEKeEhM4</a></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>