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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [WebAssembly] SIMD bit-shifts can remove unroll thanks to V8 fixes"
href="https://bugs.llvm.org/show_bug.cgi?id=42973">42973</a>
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<th>Summary</th>
<td>[WebAssembly] SIMD bit-shifts can remove unroll thanks to V8 fixes
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<th>Product</th>
<td>new-bugs
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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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>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>bvibber@wikimedia.org
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=22370" name="attach_22370" title="Patch that removes this">attachment 22370</a> <a href="attachment.cgi?id=22370&action=edit" title="Patch that removes this">[details]</a></span>
Patch that removes this
This bit in WebAssemblyTargetLowering::LowerShift
- // Expand all vector shifts until V8 fixes its implementation
- // TODO: remove this once V8 is fixed
- if (!Subtarget->hasUnimplementedSIMD128())
- return unrollVectorShift(Op, DAG);
can be removed since <a href="https://chromium-review.googlesource.com/c/v8/v8/+/1722198">https://chromium-review.googlesource.com/c/v8/v8/+/1722198</a>
fixed non-constant SIMD bit-shifts.
This gives me a speedup of several percent in dav1d AV1 decoder on my
WebAssembly SIMD branch running in Chrome Canary.
Attached patch reapplies <a href="https://reviews.llvm.org/D58800">https://reviews.llvm.org/D58800</a> which was accidentally
merged early a few months ago, then reverted.</pre>
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