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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 - TableGen does not handle AND masks correctly"
href="https://bugs.llvm.org/show_bug.cgi?id=35375">35375</a>
</td>
</tr>
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<th>Summary</th>
<td>TableGen does not handle AND masks correctly
</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>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>GlobalISel
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>diana.picus@linaro.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=19455" name="attach_19455" title="Reproducer">attachment 19455</a> <a href="attachment.cgi?id=19455&action=edit" title="Reproducer">[details]</a></span>
Reproducer
llc -O0 -mtriple armv7-- -stop-before=expand-isel-pseudos -o - pkhbt.ll
produces a PKHBT instruction, but with -global-isel it does not.
The GlobalISelEmitter for TableGen generates code to select the PKHBT pattern:
def PKHBT : APKHI<0b01101000, 0, (outs GPRnopc:$Rd),
(ins GPRnopc:$Rn, GPRnopc:$Rm, pkh_lsl_amt:$sh),
IIC_iALUsi, "pkhbt", "\t$Rd, $Rn, $Rm$sh",
[(set GPRnopc:$Rd, (or (and GPRnopc:$Rn, 0xFFFF),
(and (shl GPRnopc:$Rm, pkh_lsl_amt:$sh),
0xFFFF0000)))]>,
Requires<[IsARM, HasV6]>,
Sched<[WriteALUsi, ReadALU]>;
The problem is that it fails when trying to compare -65536 (or 4294901760) to
0xFFFF,0000. This is because the constant in the instruction is sign extended
to 64 bits (0xFFFF,FFFF,FFFF,0000) and then compared to the non-extended 64 bit
version expected by TableGen.
In contrast, the DAGISelEmitter generates special code for AND immediates
(OPC_CheckAndImm), which does not sign extend.</pre>
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