<html>
<head>
<base href="http://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Incorrect live-in information in ARM backend"
href="http://llvm.org/bugs/show_bug.cgi?id=21029">21029</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Incorrect live-in information in ARM backend
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>OS</th>
<td>other
</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: ARM
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>moritz.roth@arm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=13065" name="attach_13065" title="Reproducer for the given IR">attachment 13065</a> <a href="attachment.cgi?id=13065&action=edit" title="Reproducer for the given IR">[details]</a></span>
Reproducer for the given IR
I'm seeing cases in the ARM backend where live registers aren't contained in
the live-in set of the basic block. Take the attached .ll, which I extracted
from LNT/oggenc:
$ llc -mtriple=thumbv6m-eabi -O3 oggenc.ll -print-after-all
After the Prologue/Epilogue Insertion & Frame Finalization pass, this produces
(shortened, with ToT 22/09/2014):
BB#28: derived from LLVM BB %for.cond157.for.cond209.preheader_crit_edge
Live Ins: %R2
Predecessors according to CFG: BB#33
%R3<def> = tLDRi %R6, 0, pred:14, pred:%noreg; mem:LD4[FixedStack35]
%R5<def> = tLDRi %R6, 1, pred:14, pred:%noreg; mem:LD4[FixedStack34]
%R0<def>, %CPSR<def,dead> = tSUBrr %R5, %R3, pred:14, pred:%noreg
%R4<def> = tLDRi %R6, 5, pred:14, pred:%noreg; mem:LD4[FixedStack30]
Successors according to CFG: BB#29
BB#29: derived from LLVM BB %for.cond209.preheader
Live Ins: %R0 %R4 %R2 %R3 %R5
Predecessors according to CFG: BB#26 BB#28
%R1<def>, %CPSR<def,dead> = tADDrr %R0, %R3, pred:14, pred:%noreg
tCMPr %R1<kill>, %R4, pred:14, pred:%noreg, %CPSR<imp-def>
tBcc <BB#30>, pred:11, pred:%CPSR<kill>
Successors according to CFG: BB#30(16) BB#45(16)
BB#45:
Live Ins: %R0 %R4 %R2
Predecessors according to CFG: BB#29
tB <BB#35>, pred:14, pred:%noreg
Successors according to CFG: BB#35
BB#30: derived from LLVM BB %if.end216.lr.ph
Live Ins: %R0 %R2 %R3 %R5
Predecessors according to CFG: BB#29
%R1<def>, %CPSR<def,dead> = tLSLri %R5<kill>, 2, pred:14, pred:%noreg
tSTRi %R2<kill>, %R6, 30, pred:14, pred:%noreg; mem:ST4[FixedStack5]
%R2<def>, %CPSR<def,dead> = tLSLri %R0, 2, pred:14, pred:%noreg
%R1<def>, %CPSR<def,dead> = tSUBrr %R2, %R1<kill>, pred:14, pred:%noreg
tSTRi %R3, %R6, 0, pred:14, pred:%noreg; mem:ST4[FixedStack35]
....
%R6 is live (it contains the stack pointer) in both BB#28 and BB#30, but not in
the live-in sets of either. Since the value isn't killed or redefined anywhere,
I'd expect it to be live-in in those blocks?
I'm not aware of any miscompilations caused by this, but I'd like to use the
live-in information in an optimization pass and therefore need it to be
correct.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>