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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [EarlyCSE] Missed trivial dead store case"
href="http://llvm.org/bugs/show_bug.cgi?id=22583">22583</a>
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<th>Summary</th>
<td>[EarlyCSE] Missed trivial dead store case
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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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
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Scalar Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>listmail@philipreames.com
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</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Early CSE currently does not handle this case:
; Function Attrs: readonly
declare void @readmem() #0
define void @test(i64* %ptr) {
%v = load i64* %ptr
store i64 %v, i64* %ptr
call void @readmem()
ret void
}
attributes #0 = { readonly }
The store is dead since it's writing back the same value which was read. Given
both are simple (non volatile, non ordered) the store can just be removed.
EarlyCSE has all the information to do this. Load is part of the available
load set. We know we haven't crossed an ordering set (if available load set is
non-empty).</pre>
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