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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missing tail call for memcpy create by LoopIdiomRecognizer"
href="https://bugs.llvm.org/show_bug.cgi?id=44377">44377</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing tail call for memcpy create by LoopIdiomRecognizer
</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>
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<th>Component</th>
<td>Loop Optimizer
</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 f(unsigned char*__restrict p,unsigned char*__restrict q,int n){
for(int i=0;i<n;++i)
p[i]=q[i];
}
Current -O3 codegen:
f(unsigned char*, unsigned char*, int): # @f(unsigned char*, unsigned char*,
int)
test edx, edx
jle .LBB0_2
push rax
mov edx, edx
call memcpy
add rsp, 8
.LBB0_2:
ret
But we could have a tail cail here:
f(unsigned char*, unsigned char*, int): # @f(unsigned char*, unsigned char*,
int)
test edx, edx
je .LBB0_1
movsxd rdx, edx
jmp memcpy # TAILCALL
.LBB0_1:
ret</pre>
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