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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 - [SimplifyLibCalls] bad codegen for bcmp with constant inputs"
href="https://bugs.llvm.org/show_bug.cgi?id=41150">41150</a>
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<th>Summary</th>
<td>[SimplifyLibCalls] bad codegen for bcmp with constant inputs
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>clement.courbet@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Example: (<a href="https://gcc.godbolt.org/z/pfvPCB">https://gcc.godbolt.org/z/pfvPCB</a>)
#include <cstring>
static constexpr char k[] = "ABCDEFGH";
int F(char* p) {
return memcmp(p, k, strlen(k)) == 0;
}
With clang 7, -O2:
F(char*): # @F(char*)
movabs rcx, 5208208757389214273
xor eax, eax
cmp qword ptr [rdi], rcx
sete al
ret
With trunk, -O2:
F(char*): # @F(char*)
push rax
mov esi, offset k
mov edx, 8
call bcmp
xor ecx, ecx
test eax, eax
sete cl
mov eax, ecx
pop rcx
ret
k:
.asciz "ABCDEFGH"</pre>
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