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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Worse diagnostics for NEON instructions"
href="https://llvm.org/bugs/show_bug.cgi?id=24498">24498</a>
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<tr>
<th>Summary</th>
<td>Worse diagnostics for NEON instructions
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<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>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: AArch64
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>petr.pavlu@arm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Commit r244955 [1] introduced worse error reporting in some cases.
New behaviour (using r245428):
$ echo "fabs.4s v0, v0" | llvm-mc -triple=aarch64 -mattr=-neon -show-encoding
.text
<stdin>:1:1: error: too few operands for instruction
fabs.4s v0, v0
^
Previous behaviour (using r245428 but reverting r244955):
$ echo "fabs.4s v0, v0" | llvm-mc -triple=aarch64 -mattr=-neon -show-encoding
.text
<stdin>:1:6: error: invalid type suffix for instruction
fabs.4s v0, v0
^
What happens is that the short-form NEON matching gives
`MatchResult = Match_MissingFeature' and `ErrorInfo = 0x8' (identifier of the
missing NEON feature). Then the long-form NEON matching gives
`MatchResult = Match_InvalidOperand' and `ErrorInfo = 1' (number of an invalid
operand). However, the new code in r244955 incorrectly mixes these two together
and creates `Match_InvalidOperand' and `ErrorInfo = 0x8'.
I think LLVM should report the 'instruction requires: ...' error for this
example. This could be achieved by moving the newly introduced rewrite code
before the `switch (MatchResult) {...}' code and fixing the rewrite so it also
uses `MatchResult' from the short-form matching.
[1]
<a href="http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150810/293460.html">http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150810/293460.html</a></pre>
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