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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - "[AggressiveInstCombine] Generalize foldGuardedRotateToFunnelShift to generic funnel shifts" broke ARM/AArch64 targets"
href="https://bugs.llvm.org/show_bug.cgi?id=48068">48068</a>
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<th>Summary</th>
<td>"[AggressiveInstCombine] Generalize foldGuardedRotateToFunnelShift to generic funnel shifts" broke ARM/AArch64 targets
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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
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Transformation Utilities
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>martin@martin.st
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk
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<p>
<div>
<pre>Since "[AggressiveInstCombine] Generalize foldGuardedRotateToFunnelShift to
generic funnel shifts", git commit 59b22e495c15d2830f41381a327f5d6bf49ff416,
the following reduced test case errors triggers asserts during compilation:
$ cat apedec-reduced.c
a;
b(e) {
int c;
unsigned d = f();
c = d >> 32 - e;
return c;
}
g() {
int h = i();
if (a)
h = h << a | b(a);
return h;
}
$ clang -target aarch64-linux-gnu -w -c -O3 apedec-reduced.c
clang: ../lib/Transforms/InstCombine/InstructionCombining.cpp:3656: bool
llvm::InstCombinerImpl::run(): Assertion `DT.dominates(BB, UserParent) &&
"Dominance relation broken?"' failed.
The same happens with e.g. an armv7-linux-gnueabihf target.
The problematic commit was reverted in
36cf1e7d0e0e8aaea1f33bfa12d7a285756b75ba.</pre>
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