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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Passing of packed structures on sparc64 different than in gcc"
href="https://bugs.llvm.org/show_bug.cgi?id=40153">40153</a>
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<th>Summary</th>
<td>Passing of packed structures on sparc64 different than in gcc
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>Other
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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>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>simonas+llvm.org@kazlauskas.me
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
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<pre>This bug has been originally discovered by Michael Karcher. Filling the bug on
behalf of them.
---
As noted while filing a bug on rustc because rustc does not correctly implement
the Sparc64 ABI regarding floating point fields of "small" structures, I
stumbled across a difference between gcc an clang, as shown in
<a href="https://github.com/rust-lang/rust/issues/57103">https://github.com/rust-lang/rust/issues/57103</a> (the important piece is quoted
below):
struct str3 {
float f; // passed in most-significant half of %o0 (gcc) or in %f0 (clang)
int i; // passed in least-significant half of %o0
} __attribute__((packed));
Without __attribute__((packed)), clang, gcc and the ABI standard agree to pass
f in %f0. The ABI standard doesn't contain anything about packed structures, so
I don't see a way to decide whether gcc or clang is right. I report a bug on
both products to raise awareness.</pre>
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