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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: sin^2(a) + cos^2(a) == 1"
href="https://bugs.llvm.org/show_bug.cgi?id=35598">35598</a>
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<th>Summary</th>
<td>Missed optimization in math expression: sin^2(a) + cos^2(a) == 1
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<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>
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<th>Priority</th>
<td>P
</td>
</tr>
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<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 cos(a) * cos(a) + sin(a) * sin(a);
}
generates this assembly:
test(double): # @test(double)
sub rsp, 24
lea rdi, [rsp + 16]
lea rsi, [rsp + 8]
call sincos
vmovsd xmm1, qword ptr [rsp + 8] # xmm1 = mem[0],zero
vmovsd xmm0, qword ptr [rsp + 16] # xmm0 = mem[0],zero
vmulsd xmm0, xmm0, xmm0
vfmadd231sd xmm0, xmm1, xmm1
add rsp, 24
ret
But there is formula: sin^2(a) + cos^2(a) == 1. And it can be compiled in
faster way.</pre>
</div>
</p>
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