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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Reassociate: Unable to do reassociation"
href="http://llvm.org/bugs/show_bug.cgi?id=22487">22487</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Reassociate: Unable to do reassociation
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>3.6
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>swpenim@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider the sample code in the following section.
a, b, d, e are all multiplied by -6, and therefore can be added first
before being multiplied. This is done in llvm-3.5 release, but not in git
branch release_36.
sample code
====
int foo(int a, int b, int c, int d, int e)
{
return -6 * a + -6 * b + 10 * c + -6 *d + -6 *e;
}
====
IR Dump After "Reassociate expressions" in git branch:release_36
===
define i32 @foo(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) #0 {
entry:
%mul8 = add i32 %b, %a
%add = mul nsw i32 %mul8, 6
%mul2 = mul nsw i32 %c, 10
%add.neg = sub i32 0, %add
%add39 = add i32 %mul2, %add.neg
%mul4 = mul nsw i32 %d, 6
%mul4.neg = sub i32 0, %mul4
%add510 = add i32 %add39, %mul4.neg
%mul6 = mul nsw i32 %e, 6
%add711 = sub i32 %add510, %mul6
ret i32 %add711
}
===
IR Dump After "Reassociate expressions" in llvm-3.5 release
===
; Function Attrs: nounwind readnone uwtable
define i32 @foo(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) #0 {
entry:
%mul8 = add i32 %b, %a
%mul2 = mul nsw i32 %c, 10
%tmp = add i32 %mul8, %d
%tmp9 = add i32 %tmp, %e
%tmp10 = mul i32 %tmp9, -6
%add7 = add i32 %tmp10, %mul2
ret i32 %add7
}
===</pre>
</div>
</p>
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