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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - merge truncated stores"
href="https://bugs.llvm.org/show_bug.cgi?id=46662">46662</a>
</td>
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<tr>
<th>Summary</th>
<td>merge truncated stores
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>void i32(long long x, int* p) {
int a = x;
int b = x >> 32;
p[0] = a;
p[1] = b;
}
define void @i32(i64 %0, i32* nocapture %1) {
%3 = trunc i64 %0 to i32
%4 = lshr i64 %0, 32
%5 = trunc i64 %4 to i32
store i32 %3, i32* %1, align 4
%6 = getelementptr inbounds i32, i32* %1, i64 1
store i32 %5, i32* %6, align 4
ret void
}
--------------------------------------------------------------------------
Compiles to x86-64:
movl %edi, (%rsi)
shrq $32, %rdi
movl %edi, 4(%rsi)
retq
--------------------------------------------------------------------------
But that could be only:
movq %rdi, (%rsi)
In DAGCombiner, we have MatchStoreCombine(), but it only handles 8-bit; we have
mergeConsecutiveStores(), but it doesn't look at trunc patterns.
<a href="https://godbolt.org/z/xMPxT9">https://godbolt.org/z/xMPxT9</a></pre>
</div>
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