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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Large alignment assumptions overflow 32-bit 'unsigned', trip zero alignment assertion"
href="https://bugs.llvm.org/show_bug.cgi?id=45131">45131</a>
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<th>Summary</th>
<td>Large alignment assumptions overflow 32-bit 'unsigned', trip zero alignment assertion
</td>
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>9.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>FreeBSD
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>LLVM Codegen
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>cem@FreeBSD.org
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>Assertion failed: (Alignment != 0 && "Invalid Alignment"), function
CreateAlignmentAssumption, file llvm-project/llvm/include/llvm/IR/IRBuilder.h,
line 2573.
1. <eof> parser at end of file
2. Per-file LLVM IR generation
3. ../../v8/src/common/ptr-compr-inl.h:30:19: Generating code for
declaration 'v8::internal::GetIsolateRoot'
FreeBSD clang version 9.0.1 (<a href="mailto:git@github.com">git@github.com</a>:llvm/llvm-project.git
c1a0a213378a458fbea1a5c77b315c7dce08fd05) (based on LLVM 9.0.1)
Target: x86_64-unknown-freebsd13.0
Thread model: posix
This is tickled by Chrome's v8 engine, which asserts 4GB alignment with
something like:
__builtin_assume_aligned(foo, size_t{4} * GB)
in an inlined function, GetIsolateRoot().
The assertion tripped seems to be in CreateAlignmentAssumption(), which takes
an 'unsigned Alignment' and asserts it is non-zero. 2^32 mod 2^32 is zero, so
the assertion fires. For now I am working around this issue by disabling use
of __builtin_assume_aligned() in v8.</pre>
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