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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - compiler crash when optimizing multiple _mm_hsub_epi16 intrinsics in certain pattern"
href="https://bugs.llvm.org/show_bug.cgi?id=51974">51974</a>
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<th>Summary</th>
<td>compiler crash when optimizing multiple _mm_hsub_epi16 intrinsics in certain pattern
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>benjsith@gmail.com
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, pengfei.wang@intel.com, spatel+llvm@rotateright.com
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<pre>Created <span class=""><a href="attachment.cgi?id=25294" name="attach_25294" title="Compiler output with error log/callstack">attachment 25294</a> <a href="attachment.cgi?id=25294&action=edit" title="Compiler output with error log/callstack">[details]</a></span>
Compiler output with error log/callstack
I ran into a compiler crash when compiling some SSE code. It appears to stem
from optimizing a specific dataflow for some intrinsics, which causes the DAG
to have cycles. A debug build asserts, while a release build infinitely loops.
The following is a minimal repro example:
#include <immintrin.h>
__m128i do_stuff(__m128i A) {
__m128i B = _mm_hadd_epi16(A, A);
__m128i C = _mm_hadd_epi16(B, A);
return C;
}
when compiled with `clang -O1 -msse4` it exhibits the issue. It also appears to
repro if both intrinsics are changed to one of _mm_hadd_epi32, _mm_hsub_epi16,
or _mm_hsub_epi32. It does not repro with -O0.
I've attached the error output I get from the compiler showing more details
including the state of the DAG and a callstack
I tested this on trunk at commit 9820dd970c1b72c7f77fad647b762053e2f60e31 and
confirmed it's still present. It happens both on Windows and Linux.</pre>
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