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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed optimization for A && !B"
href="https://bugs.llvm.org/show_bug.cgi?id=50389">50389</a>
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<th>Summary</th>
<td>Missed optimization for A && !B
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
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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
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>mvels@google.com
</td>
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
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<pre>The ABI dictates that bool be strictly 0 or 1. A bool value outside of 0 or 1
is UB
The compiler can optimize `A && !B1 then as `A > B`, which say under x86
becomes the macro fused op:
AAndNotBAlt(bool, bool):
cmp dil, sil
jbe .LBB1_1
instead, the compiler generates:
<a href="https://gcc.godbolt.org/z/EWx63b4nz">https://gcc.godbolt.org/z/EWx63b4nz</a>
AAndNotB(bool, bool):
test edi, edi
je .LBB0_2
test sil, sil
jne .LBB0_2
jmp True()</pre>
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