<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/54222>54222</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            missing tautological-compare warning for float == double constant 
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            good first issue,
            c,
            c++,
            clang:diagnostics
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          zygoloid
      </td>
    </tr>
</table>

<pre>
    Example:
```c++
float f = 0.1;
if (f == 0.1) { ... }
```

This is a tautological comparison: the LHS of the comparison is always a `float` value promoted to `double`, and the RHS of the comparison is a value that cannot result from a `float`-to-`double` promotion.

We should probably also warn on `f != non_float_constant`; such comparisons are not tautological, but are equivalent to `!isnan(f)`. We shouldn't warn if the constant value is exactly representable in type `float`. And don't warn on `<`, `<=`, `>=`, `>`, `<=>`.
</pre>
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