<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/104050>104050</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Why are general-purpose registers and floating-point registers stored on both sides of fp in the Aarch64 architecture
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          Wang-Zhongqi
      </td>
    </tr>
</table>

<pre>
    Hello everyone, I have a question. Why are the callee saved general-purpose registers and callee saved floating-point registers stored on both sides of fp and lr respectively in the aarch64 architecture c callconv? This may be the case in the stack:
-- stack --
| saved x28  |
| saved x27  |
| saved lr      |
| saved fp | <- new fp
| saved d9    |
| saved d8    |

When I did not use the called saved floating-point register, I used LLVMBuildAlloc to generate a structure and obtained the space below fp. During the backtrace process, I used * (fp-8) to obtain the value I needed. The stack frame structure is as follows:
| saved x28  |
| saved x27  |
| saved lr      |
| saved fp     | <- new fp
| frame_type | <- value
| context ptr |

However, when using the callee saved floating-point register, the stack frame structure changed, making it impossible for me to obtain values through the original method. The specific stack frame structure may be as follows:
| saved x28  |
| saved x27  |
| saved lr      |
| saved fp     | <- new fp
| saved d9    | <- inserted in the middle
| saved d8 |
| frame_type | <- value
| context ptr  |

If I want to save some values adjacent to fp for retrieval during backtrace, how can I implement it through llvm17 c-API?
I have considered preserving registers to avoid using d8-d31, but I only found+reserve-x0 in -- attr, which only provides the option to preserve general-purpose registers.
</pre>
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