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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LLVM should model TLSDESC accessor as clobbering NZCV"
href="https://bugs.llvm.org/show_bug.cgi?id=40504">40504</a>
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<th>Summary</th>
<td>LLVM should model TLSDESC accessor as clobbering NZCV
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: AArch64
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>peter@pcc.me.uk
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<th>CC</th>
<td>arnaud.degrandmaison@arm.com, llvm-bugs@lists.llvm.org, peter.smith@linaro.org, Ties.Stuij@arm.com
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<pre>While reviewing Android's proposed implementation of TLSDESC:
<a href="https://android-review.googlesource.com/c/platform/bionic/+/886118">https://android-review.googlesource.com/c/platform/bionic/+/886118</a>
I noticed that it does not attempt to preserve NZCV. LLVM's model of TLSDESC,
on the other hand, assumes that NZCV is preserved:
<a href="http://llvm-cs.pcc.me.uk/lib/Target/AArch64/AArch64InstrInfo.td#1639">http://llvm-cs.pcc.me.uk/lib/Target/AArch64/AArch64InstrInfo.td#1639</a>
glibc's implementation of TLSDESC doesn't look like it attempts to preserve
NZCV either:
<a href="https://github.com/bminor/glibc/blob/e1e47c912a8e557508362715f7468091def3ec4f/sysdeps/aarch64/dl-tlsdesc.S">https://github.com/bminor/glibc/blob/e1e47c912a8e557508362715f7468091def3ec4f/sysdeps/aarch64/dl-tlsdesc.S</a>
I think that what this means is that we should add NZCV to the list of clobbers
for the TLSDESC accessor.</pre>
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