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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 - Missed optimization in math expression: tan(a) * cos(a) == sin(a)"
href="https://bugs.llvm.org/show_bug.cgi?id=35602">35602</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed optimization in math expression: tan(a) * cos(a) == sin(a)
</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>All
</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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@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 '--std=c++17 -O3 -march=native -ffast-math' flags for this
code:
#include <cmath>
double test(double a)
{
return tan(a) * cos(a);
}
generates this assembly:
test(double): # @test(double)
sub rsp, 24
vmovsd qword ptr [rsp + 8], xmm0 # 8-byte Spill
call tan
vmovsd qword ptr [rsp + 16], xmm0 # 8-byte Spill
vmovsd xmm0, qword ptr [rsp + 8] # 8-byte Reload
call cos
vmulsd xmm0, xmm0, qword ptr [rsp + 16] # 8-byte Folded Reload
add rsp, 24
ret
gcc(trunk) with '--std=c++17 -O3 -march=native -ffast-math' flags generates
this:
test(double):
jmp sin</pre>
</div>
</p>
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