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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - GVN can't remove trivially identical operations in zlib"
href="http://llvm.org/bugs/show_bug.cgi?id=22005">22005</a>
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<th>Summary</th>
<td>GVN can't remove trivially identical operations in zlib
</td>
</tr>
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<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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>david.majnemer@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>consider:
target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i64 @f(i8* %out, i8* %end) {
%1 = icmp ult i8* %out, %end
br i1 %1, label %2, label %6
; <label>:2 ; preds = %0
%3 = ptrtoint i8* %end to i64
%4 = ptrtoint i8* %out to i64
%5 = sub i64 %3, %4
br label %10
; <label>:6 ; preds = %0
%7 = ptrtoint i8* %out to i64
%8 = ptrtoint i8* %end to i64
%9 = sub i64 %8, %7
br label %10
; <label>:10 ; preds = %6, %2
%.in = phi i64 [ %5, %2 ], [ %9, %6 ]
%11 = add i64 %.in, 257
ret i64 %11
}
both sub operations are computing end-out</pre>
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