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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - DependenceAnalysis is not access size aware."
href="http://llvm.org/bugs/show_bug.cgi?id=15811">15811</a>
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<th>Summary</th>
<td>DependenceAnalysis is not access size aware.
</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>All
</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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Global Analyses
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>etherzhhb@gmail.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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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=10398" name="attach_10398" title="The patch to add the fail case.">attachment 10398</a> <a href="attachment.cgi?id=10398&action=edit" title="The patch to add the fail case.">[details]</a></span>
The patch to add the fail case.
Consider the following function:
define i64 @alias(i32* nocapture %A) nounwind uwtable {
entry:
%arrayidx = getelementptr inbounds i32* %A, i64 1
store i32 2, i32* %arrayidx, align 4
%0 = bitcast i32* %A to i64*
%1 = load i64* %0, align 8
ret i64 %1
}
Ignoring size of the memory location accessed in
store i32 2, i32* %arrayidx, align 4
and
%1 = load i64* %0, align 8,
The addresses pointed by %arrayidx and %0 doesn't alias each other, and hence
DependenceAnalysis claims there is not dependencies from the store to the load,
and gives the following output:
da analyze - none!
da analyze - none!
da analyze - none!
However, the above result is incorrect (at least for x86), there should be a
dependency from from the store to the load, because the memory location written
by the store overlap with the memory location read by the load.</pre>
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