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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Stackmaps liveness analysis can determine RIP is live"
href="http://llvm.org/bugs/show_bug.cgi?id=21266">21266</a>
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<th>Summary</th>
<td>Stackmaps liveness analysis can determine RIP is live
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>kmod@dropbox.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
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</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=13199" name="attach_13199" title="Test case -- reproduce with "llc rip.ll"">attachment 13199</a> <a href="attachment.cgi?id=13199&action=edit" title="Test case -- reproduce with "llc rip.ll"">[details]</a></span>
Test case -- reproduce with "llc rip.ll"
Here's a snippet of the machine ir before stackmaps liveness analysis:
BB#1: derived from LLVM BB %1, Align 4 (16 bytes)
Live Ins: %RBP
Predecessors according to CFG: BB#1 BB#0
PATCHPOINT 30697712, 13, 8441600, 0, 0, <regmask>, %RSP<imp-def>,
%RAX<imp-def,dead>, ...
%RAX<def> = MOV64rm %RIP, 1, %noreg, <ga:@edgecount>, %noreg;
mem:LD8[@edgecount]
%RAX<def,tied1> = INC64r %RAX<kill,tied0>, %EFLAGS<imp-def,dead>
CMP64ri32 %RAX<kill>, 10001, %EFLAGS<imp-def>
JL_4 <BB#1>, %EFLAGS<imp-use,kill>
Successors according to CFG: BB#2(4) BB#1(124)
And here's what happens in stackmap liveness:
********** COMPUTING STACKMAP LIVENESS: f_e1_1 **********
[snip]
****** BB ******
Live Registers: %RBP %EBP %BP %BPL
JL_4 <BB#1>, %EFLAGS<imp-use,kill>
Live Registers: %RBP %EBP %BP %BPL %EFLAGS
CMP64ri32 %RAX<kill>, 10001, %EFLAGS<imp-def>
Live Registers: %RBP %EBP %BP %BPL %RAX %EAX %AX %AL %AH
%RAX<def,tied1> = INC64r %RAX<kill,tied0>, %EFLAGS<imp-def,dead>
Live Registers: %RBP %EBP %BP %BPL %RAX %EAX %AX %AL %AH
%RAX<def> = MOV64rm %RIP, 1, %noreg, <ga:@edgecount>, %noreg;
mem:LD8[@edgecount]
Live Registers: %RBP %EBP %BP %BPL %RIP %EIP %IP
PATCHPOINT 30697712, 13, 8441600, 0, 0, <regmask>, <regliveout>,
%RSP<imp-def>, %RAX<imp-def,dead>, ...
[snip]
llc:
/opt/kmod_unenc/pyston_deps/llvm-test/lib/CodeGen/TargetRegisterInfo.cpp:124:
const llvm::TargetRegisterClass*
llvm::TargetRegisterInfo::getMinimalPhysRegClass(unsigned int, llvm::EVT)
const: Assertion `BestRC && "Couldn't find the register class"' failed.
It looks like the stackmaps liveness analysis is seeing the RIP-relative load
as a usage of %RIP that establishes its liveness, which causes the stackmap
emission to fail.</pre>
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