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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - (New)GVN doesn't look through non-constant memcpy"
href="http://bugs.llvm.org/show_bug.cgi?id=32570">32570</a>
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<th>Summary</th>
<td>(New)GVN doesn't look through non-constant memcpy
</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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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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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</tr>
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<th>Reporter</th>
<td>keno@alumni.harvard.edu
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>E.g. in this example, GVN can't turn this into `load a[100]`:
```
declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i32, i1)
define double @trivial_memcpy(<200 x double> *%a) {
%b = alloca <200 x double>
%acast = bitcast <200 x double> *%a to i8*
%bcast = bitcast <200 x double> *%b to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %bcast, i8* %acast, i64 1600, i32
8, i1 0)
%innerptr = getelementptr <200 x double>, <200 x double> *%a, i32 0, i32
100
%inner = load double, double *%innerptr
ret double %inner
}
```
Now for this particular example, SROA does do this optimization, but this feels
like something that GVN should be able to do as well.</pre>
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