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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DAGCombine] Difference in behaviour for SDIV undef, %X on scalar and vector types"
href="https://bugs.llvm.org/show_bug.cgi?id=36305">36305</a>
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<th>Summary</th>
<td>[DAGCombine] Difference in behaviour for SDIV undef, %X on scalar and vector types
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<p>
<div>
<pre>llvm\test\CodeGen\X86\combine-sdiv.ll
; fold (sdiv undef, x) -> 0
define i32 @combine_sdiv_undef0(i32 %x) {
; CHECK-LABEL: combine_sdiv_undef0:
; CHECK: # %bb.0:
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: retq
%1 = sdiv i32 undef, %x
ret i32 %1
}
define <4 x i32> @combine_vec_sdiv_undef0(<4 x i32> %x) {
; CHECK-LABEL: combine_vec_sdiv_undef0:
; CHECK: # %bb.0:
; CHECK-NEXT: retq
%1 = sdiv <4 x i32> undef, %x
ret <4 x i32> %1
}
Scalar divisions by undef combine to zero, while vectors combine to undef.
Similar behaviour for udiv, srem, urem.</pre>
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