<html>
<head>
<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 - Missed opportunity for store elimination"
href="https://bugs.llvm.org/show_bug.cgi?id=47887">47887</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed opportunity for store elimination
</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>float r;
void t1( int& x)
{
++x;
r = 0;
--x;
}
void t2( int& x, float& rr )
{
++x;
rr = 0;
--x;
}
char c;
void t3( int& x, char& rr )
{
++x;
c = 0;
--x;
}
void t4( int& x, char& cc )
{
++x;
cc = 0;
--x;
}
Clang -O3:
t1(int&): # @t1(int&)
mov eax, dword ptr [rdi]
mov dword ptr [rip + r], 0
mov dword ptr [rdi], eax
ret
t2(int&, float&): # @t2(int&, float&)
mov eax, dword ptr [rdi]
mov dword ptr [rsi], 0
mov dword ptr [rdi], eax
ret
t3(int&, char&): # @t3(int&, char&)
mov eax, dword ptr [rdi]
mov byte ptr [rip + c], 0
mov dword ptr [rdi], eax
ret
t4(int&, char&): # @t4(int&, char&)
add dword ptr [rdi], 1
mov byte ptr [rsi], 0
add dword ptr [rdi], -1
ret
r:
.long 0x00000000 # float 0
c:
.byte 0 # 0x0
ICC -O3:
t1(int&):
mov DWORD PTR r[rip], 0 #7.5
ret #9.1
t2(int&, float&):
mov DWORD PTR [rsi], 0 #15.5
ret #17.1
t3(int&, char&):
mov BYTE PTR c[rip], 0 #24.5
ret #26.1
t4(int&, char&):
inc DWORD PTR [rdi] #30.7
mov BYTE PTR [rsi], 0 #31.5
dec DWORD PTR [rdi] #32.7
ret #33.1
r:
c:
Godbolt:
<a href="https://godbolt.org/z/zh35ch">https://godbolt.org/z/zh35ch</a></pre>
</div>
</p>
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