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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - SDAG failure on AVX512BW/AVX512VL"
href="https://llvm.org/bugs/show_bug.cgi?id=25684">25684</a>
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<tr>
<th>Summary</th>
<td>SDAG failure on AVX512BW/AVX512VL
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>congh@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>LLVM fails to select instructions for the following IR on AVX512BW/AVX512VL (OK
on other AVX512 sets):
define void @truncate_v16i16_to_v16i8(<16 x i16> %a) {
%1 = trunc <16 x i16> %a to <16 x i8>
store <16 x i8> %1, <16 x i8>* undef, align 4
ret void
}
The error message on AVX512BW:
.section __TEXT,__text,regular,pure_instructions
LLVM ERROR: Cannot select: t9: ch = store<ST16[undef](align=4), trunc to v16i8>
t0, t2, undef:i64, undef:i64
t2: v16i16,ch = CopyFromReg t0, Register:v16i16 %vreg0
t1: v16i16 = Register %vreg0
t4: i64 = undef
t4: i64 = undef
In function: truncate_v16i16_to_v16i8
The error message on AVX512VL:
.section __TEXT,__text,regular,pure_instructions
LLVM ERROR: Cannot select: t6: ch = store<ST16[undef](align=4)> t0, t10,
undef:i64, undef:i64
t10: v16i8 = X86ISD::VTRUNC t9
t9: v16i32 = X86ISD::VSEXT t2
t2: v16i16,ch = CopyFromReg t0, Register:v16i16 %vreg0
t1: v16i16 = Register %vreg0
t4: i64 = undef
t4: i64 = undef
In function: truncate_v16i16_to_v16i8</pre>
</div>
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