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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [PATCH] armv5te thumb1 target generated UB code mov tGPR, tGPR (should => adds GPR,GPR,#0)"
href="http://llvm.org/bugs/show_bug.cgi?id=17921">17921</a>
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<th>Summary</th>
<td>[PATCH] armv5te thumb1 target generated UB code mov tGPR, tGPR (should => adds GPR,GPR,#0)
</td>
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<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
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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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: ARM
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>dontbugme@mailinator.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
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<pre>Dear LLVM ARM backend developers,
llc generates invalid armv5te code, as per
<a href="https://android.googlesource.com/toolchain/binutils/+/92337cf27b1497415e3f345ea9292e96ced2a8fa">https://android.googlesource.com/toolchain/binutils/+/92337cf27b1497415e3f345ea9292e96ced2a8fa</a>
The following patch is a sketch, still somewhat problematic - it should be
active only for armv5te thumb1, and the CPSR clobber might have some unintended
consequences (perhaps this belongs somewhere else than copyPhysReg?)
Someone more well-versed in ARM target please take a look at it.
- anonymous
Index: lib/Target/ARM/Thumb1InstrInfo.cpp
===================================================================
--- lib/Target/ARM/Thumb1InstrInfo.cpp (revision 194564)
+++ lib/Target/ARM/Thumb1InstrInfo.cpp (working copy)
@@ -40,10 +40,17 @@
void Thumb1InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I, DebugLoc DL,
unsigned DestReg, unsigned SrcReg,
bool KillSrc) const {
+
+ if (isARMLowRegister(SrcReg) && isARMLowRegister(DestReg)) {
+ AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::tADDrr),
DestReg).addReg(ARM::CPSR) // s suffix
+ .addReg(SrcReg, getKillRegState(KillSrc)).addImm(0));
+ return;
+ }
+
AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::tMOVr), DestReg)
.addReg(SrcReg, getKillRegState(KillSrc)));
assert(ARM::GPRRegClass.contains(DestReg, SrcReg) &&
"Thumb1 can only copy GPR registers");
}</pre>
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