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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Incorrect ROR_C implementation."
href="https://bugs.llvm.org/show_bug.cgi?id=32986">32986</a>
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<th>Summary</th>
<td>Incorrect ROR_C implementation.
</td>
</tr>
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<th>Product</th>
<td>lldb
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
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<th>Reporter</th>
<td>andrea@inversepath.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Hi.
It appears that the ROR_C function, within the common utilities for the
ARM/Thumb Instruction Set Architecture, is incorrectly implemented.
>From lldb/source/Plugins/Process/Utility/ARMUtils.h:
static inline uint32_t ROR_C(const uint32_t value, const uint32_t amount,
uint32_t &carry_out, bool *success) {
...
carry_out = Bit32(value, 31);
...
However according to the ARMv6-M Architecture Reference Manual (page A2-34)
ROR_C is implemented as follows in relation to the carry_out:
...
m = shift MOD N;
result = LSR(x,m) OR LSL(x,N-m);
carry_out = result<N-1>;
...
Therefore I believe that the ROR_C function in ARMUtils.h should use the
result, rather than the value, when setting carry_out:
carry_out = Bit32(result, 31);
A comparable fix was effective in passing tests in another project I
contributed:
<a href="https://github.com/abarisani/ARMv6m_Simulator/commit/36e73fb1924edada7d75b15dcf51aa4683f0d729">https://github.com/abarisani/ARMv6m_Simulator/commit/36e73fb1924edada7d75b15dcf51aa4683f0d729</a></pre>
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