<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 comparison folding optimization"
href="https://bugs.llvm.org/show_bug.cgi?id=50008">50008</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing comparison folding optimization
</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>All
</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>juneyoung.lee@sf.snu.ac.kr
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Optimization
(cond ? ptr + 1 : ptr == ptr) --> !cond
is missing in clang.
<a href="https://godbolt.org/z/e7W5WrK5M">https://godbolt.org/z/e7W5WrK5M</a>
bool not_cond(char *x, bool cond) {
char *y = x;
if (cond)
y = x + 1;
return x == y;
}
g++ -O3 (x86-64):
mov eax, esi
xor eax, 1
ret
clang -O3 (x86-64):
lea rax, [rdi + 1]
test esi, esi
cmove rax, rdi
cmp rax, rdi
sete al
ret
Similarly for AArch64.
It seems the middle-end optimization cannot fold this:
```
%add.ptr = getelementptr inbounds i8, i8* %x, i64 1
%spec.select = select i1 %cond, i8* %add.ptr, i8* %x
%cmp = icmp eq i8* %spec.select, %x
```</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>