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<base href="https://bugs.llvm.org/">
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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 - Opportunity to remove null pointer checks (IPO)"
href="https://bugs.llvm.org/show_bug.cgi?id=46949">46949</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Opportunity to remove null pointer checks (IPO)
</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>Interprocedural 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>void clean(void);
__attribute__((noinline))
static void check(void *p)
{
if (!p)
clean();
}
void foo(void *p, void *q)
{
if (p)
check(p);
if (q)
check(q);
}
void bar(void *p, void *q)
{
check(p);
check(q);
}
foo(void*, void*): # @foo(void*, void*)
push rbx
mov rbx, rsi
test rdi, rdi
je .LBB0_2
call check(void*)
.LBB0_2:
test rbx, rbx
je .LBB0_3
mov rdi, rbx
pop rbx
jmp check(void*) # TAILCALL
.LBB0_3:
pop rbx
ret
check(void*): # @check(void*)
test rdi, rdi
je .LBB1_2
ret
.LBB1_2:
jmp clean() # TAILCALL
bar(void*, void*): # @bar(void*, void*)
push rbx
mov rbx, rsi
call check(void*)
mov rdi, rbx
pop rbx
jmp check(void*) # TAILCALL
There is a missed opportunity to remove null pointer checks (optimize "foo" to
"bar").
<a href="https://godbolt.org/z/or9oW5">https://godbolt.org/z/or9oW5</a></pre>
</div>
</p>
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