<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/77220>77220</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Handle `f(-x)=f(x)` for even functions and `f(-x)=-f(x)` for odd functions
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          k-arrows
      </td>
    </tr>
</table>

<pre>
    Currently, Clang handles this for trigonometric functions (`sin`, `cos`, and `tan`). 
https://godbolt.org/z/eharx1Gn4

However, for example, Clang doesn't currently handle this for the error function (`erf`).
https://godbolt.org/z/33W9Eharo
```c
#include<math.h>

double test_erf1(double x)
{
   return -erf(-x);
}

double test_erf2(double x)
{
   return erf(x);
}
``` 

There are many other functions we have to check, but I think the following GCC test is helpful.
https://github.com/gcc-mirror/gcc/blob/master/gcc/testsuite/gcc.dg/torture/builtin-symmetric-1.c
</pre>
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