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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed optimization in math expression: optimize double comparing"
href="https://bugs.llvm.org/show_bug.cgi?id=35844">35844</a>
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<th>Summary</th>
<td>Missed optimization in math expression: optimize double comparing
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>zamazan4ik@tut.by
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>clang trunk with '-O3 -ffast-math -std=c++17' for this code:
double test(double x, double y)
{
if(x != y)
{
return 42.0;
}
return x/y;
}
generates this code:
.LCPI0_0:
.quad 4631107791820423168 # double 42
test(double, double): # @test(double, double)
ucomisd xmm0, xmm1
je .LBB0_2
movsd xmm0, qword ptr [rip + .LCPI0_0] # xmm0 = mem[0],zero
ret
.LBB0_2:
divsd xmm0, xmm1
ret
but we can optimize here divide operation and just return 1.0.</pre>
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