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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [AArch64][CodeGen][CodeSize] Redundant 'and' can be remove with shifts in addr mode"
href="https://bugs.llvm.org/show_bug.cgi?id=34753">34753</a>
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<th>Summary</th>
<td>[AArch64][CodeGen][CodeSize] Redundant 'and' can be remove with shifts in addr mode
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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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>Windows NT
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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
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<th>Component</th>
<td>Backend: AArch64
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>mcrosier@codeaurora.org
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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>Test case:
int test(unsigned long long a, unsigned long long b, int *table) {
return table[(a * b) >> 58];
}
Current assembly:
test: // @test
// BB#0: // %entry
mul x8, x1, x0
lsr x8, x8, #56
and x8, x8, #0xfc
ldr w0, [x2, x8]
ret
We should be able to remove the 'and' for a code size with as follows:
test: // @test
// BB#0: // %entry
mul x8, x1, x0
lsr x8, x8, #58
ldr w0, [x2, x8, lsl#2]
ret
I'm not interested in pursuing this optimization, but I figured I'd file the
bug, regardless.</pre>
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