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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - get_local and set_local elimination opportunities"
href="https://llvm.org/bugs/show_bug.cgi?id=27357">27357</a>
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<th>Summary</th>
<td>get_local and set_local elimination opportunities
</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>
</tr>
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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>
</tr>
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<th>Component</th>
<td>Backend: WebAssembly
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>alonzakai@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Binaryen's simplify-locals pass removes get_locals that the backend doesn't,
and in some cases also a set_local or two. For example on fannkuch it removes
206 out of 3035 (7%) get_locals, and one set_local out of 1419.
STR: build a program then run binaryen shell --metrics --simplify-locals
--metrics and it will print out how many it removed.
He's an example text diff from fannkuch:
- (set_local $$19
- (i32.add
- (get_local $$15)
- (i32.const -1)
- )
- )
(set_local $$14
(i32.add
(get_local $$14)
(i32.const -4)
)
)
(set_local $$13
(i32.const 1)
)
(set_local $$15
- (get_local $$19)
+ (set_local $$19
+ (i32.add
+ (get_local $$15)
+ (i32.const -1)
+ )
+ )
)
so it "sinks" that set_local down into the get_local, which is eliminated.
Talking to sunfish about this, he said he already knows what's going on here.</pre>
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