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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong promotion of vector to integer bitcast on big-endian targets"
href="https://bugs.llvm.org/show_bug.cgi?id=44135">44135</a>
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<th>Summary</th>
<td>Wrong promotion of vector to integer bitcast on big-endian targets
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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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>mikael.holmen@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Reproducer:
;RUN: llc -O0 -mtriple=armebv7 -target-abi apcs -o - %s
-stop-before=finalize-isel | FileCheck %s
; Stop somewhere soon after isel.
@vec6_p = external global <6 x i16>
define i32 @foo() {
bb.0:
%vec6 = load <6 x i16>, <6 x i16>* @vec6_p, align 1
br label %bb.1
bb.1:
%0 = bitcast <6 x i16> %vec6 to i96
%1 = trunc i96 %0 to i32
ret i32 %1
}
; CHECK-LABEL: bb.1.bb.1:
; CHECK: [[REG0:%[0-9]+]]:qpr = VREV32q16 {{%[0-9]+}}
; CHECK: [[REG1:%[0-9]+]]:dpr = COPY [[REG0]].dsub_1
; CHECK: {{%[0-9]+}}:gpr = VGETLNi32 killed [[REG1]], 0
In the SelectionDAG printouts we see
Type-legalized selection DAG: %bb.1 'foo:bb.1'
SelectionDAG has 9 nodes:
t0: ch = EntryToken
t2: v8i16,ch = CopyFromReg t0, Register:v8i16 %0
t17: v4i32 = bitcast t2
t23: i32 = extract_vector_elt t17, Constant:i32<3>
t8: ch,glue = CopyToReg t0, Register:i32 $r0, t23
t9: ch = ARMISD::RET_FLAG t8, Register:i32 $r0, t8:1
and I think here the extract_vector_elt is wrong and extracts the value
from the wrong index.
The program program should return the 32 bits made up of the elements at
index 4 and 5 in the vec6 array, but with
t23: i32 = extract_vector_elt t17, Constant:i32<3>
as far as I can tell, we will extract values that originally didn't even
exist in the vec6 vectore.
If we would instead extract the element at index 2 we would get the wanted
values.</pre>
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