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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 --- - Regression: ARM jump table miscompilation" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23627&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=TJEJOVsNzhzqWN8Tm_RpbTKGTEoc3tKyj75zOflXtCo&s=p4FV4AgpTx4I904ew_xuM9YdLVewY0M0VZGJr4wa504&e=">23627</a>
</td>
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<th>Summary</th>
<td>Regression: ARM jump table miscompilation
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<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>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: ARM
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>peter@pcc.me.uk
</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=14366" name="attach_14366" title="source">attachment 14366</a> <a href="attachment.cgi?id=14366&action=edit" title="source">[details]</a></span>
source
Given the attached hist.cc, after reverting r237972:
$ clang -march=armv7-a -mtune=generic-armv7-a -mfpu=vfpv3-d16
-mfloat-abi=softfp -mthumb -target arm-linux-androideabi -Oz
-fomit-frame-pointer -fno-exceptions -fno-rtti -fno-threadsafe-statics
-std=gnu++11 -S -w hist.cc
produces the attached hist.s. The miscompiled code starts on line 564:
@ BB#26:
adr.w r0, .LJTI1_0
add.w r0, r0, r1, lsl #2
.LCPI1_48:
tbh [r0, r1, lsl #1]
.align 2
@ BB#27:
.LCPI1_49:
.long 600000 @ 0x927c0
@ BB#28:
.LJTI1_0:
.short (.LBB1_29-(.LCPI1_48+4))/2
.short (.LBB1_32-(.LCPI1_48+4))/2
.short (.LBB1_42-(.LCPI1_48+4))/2
.short (.LBB1_38-(.LCPI1_48+4))/2
.short (.LBB1_41-(.LCPI1_48+4))/2
In this code the tbh instruction ends up loading from .LJTI_0 + (r1 << 2) + (r1
<< 1) instead of the intended .LJTI0 + (r1 << 1).</pre>
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