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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - llvm appears to be miscalculating the live-out registers at a patchpoint"
href="https://bugs.webkit.org/show_bug.cgi?id=152510">152510</a>
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<th>Summary</th>
<td>llvm appears to be miscalculating the live-out registers at a patchpoint
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<th>Classification</th>
<td>Unclassified
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<th>Product</th>
<td>WebKit
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<th>Version</th>
<td>WebKit Nightly Build
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<th>Hardware</th>
<td>Unspecified
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<th>OS</th>
<td>Unspecified
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>sbarati@apple.com
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<th>CC</th>
<td>benjamin@webkit.org, fpizlo@apple.com, ggaren@apple.com, gskachkov@gmail.com, juergen@apple.com, keith_miller@apple.com, mark.lam@apple.com, msaboff@apple.com, oliver@apple.com, sukolsak@gmail.com, utatane.tea@gmail.com
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<pre>Created <span class=""><a href="attachment.cgi?id=267798" name="attach_267798" title="dfg and llvm IR.">attachment 267798</a> <a href="attachment.cgi?id=267798&action=edit" title="dfg and llvm IR.">[details]</a></span>
dfg and llvm IR.
We end up clobbering a volatile register with a C call we make even though that register is used immediately after the patchpoint.
The problem appears to be that we’re not claiming that x1 is live-out at the patchpoint w/ patchpointID=27.
The code generated for this patchpoint is at “0x146cfa588”. You can see some of the meta-data we have for this
patchpoint by looking at this line in the IR dump:
```
(#27, offset = 488, flags = 0, locations = [(Register, %r11, off:0, size:8), (Register, %r8, off:0, size:8)], liveOuts = [(%r12, 8)])
```
x1 should be live-out here because the instructions emitted immediately after the patchpoint load from x1. x1 is also a hoisted constant.</pre>
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