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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - `-mattr` should be encoded in the IR for LTO's sake"
href="https://bugs.llvm.org/show_bug.cgi?id=51161">51161</a>
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<th>Summary</th>
<td>`-mattr` should be encoded in the IR for LTO's sake
</td>
</tr>
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<th>Product</th>
<td>lld
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>twd2.me@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, smithp352@googlemail.com
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=25046" name="attach_25046" title="The diagnostic information.">attachment 25046</a> <a href="attachment.cgi?id=25046&action=edit" title="The diagnostic information.">[details]</a></span>
The diagnostic information.
When compiling the following code with LTO:
```
$ cat test.c
void _start()
{
asm volatile (
".balign 4\n\t"
"c.nop\n\t"
".balign 4\n\t"
"c.nop"
);
}
$ clang -march=rv64imac -O2 -flto -mno-relax -c test.c
$ ld.lld test.o
```
lld fails with `unable to write nop sequence of 2 bytes`.
The diagnostic information is attached.
It looks like to be due to the `HasStdExtC` check failure in
`RISCVAsmBackend::writeNopData`.
And, if I use `ld.lld -mllvm -mattr=+c test.o`, lld can generate proper machine
code.
According to Nick Desaulniers [1], `-mattr` should be encoded in the IR for
LTO's sake.
My LLVM version: commit 1b61d837b9d0 ("[Inline] Add test for PR50589 (NFC)")
[1]
<a href="https://lore.kernel.org/linux-riscv/CAKwvOdmNji0AbYUiOSfb5cLD+g7YCpXk4oDupa8gTfgzYmxvBg@mail.gmail.com/">https://lore.kernel.org/linux-riscv/CAKwvOdmNji0AbYUiOSfb5cLD+g7YCpXk4oDupa8gTfgzYmxvBg@mail.gmail.com/</a></pre>
</div>
</p>
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