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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - SCEV: Assertion `L && L->getHeader() == P->getParent()' failed in getRangeForUnknownRecurrence"
href="https://bugs.llvm.org/show_bug.cgi?id=49856">49856</a>
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<th>Summary</th>
<td>SCEV: Assertion `L && L->getHeader() == P->getParent()' failed in getRangeForUnknownRecurrence
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>max.kazantsev@azul.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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</tr></table>
<p>
<div>
<pre>The following test fails with opt -analyze -scalar-evolution:
target datalayout =
"e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:1-p2:32:8:8:32-ni:2"
target triple = "x86_64-unknown-linux-gnu"
define void @test() {
bb:
br label %bb1
bb1: ; preds = %bb
br label %bb5
bb2: ; preds = %bb2
br label %bb2
bb3: ; preds = %bb3
br label %bb3
bb4: ; preds = %bb4
br label %bb4
bb5: ; preds = %bb9, %bb1
%tmp = phi i32 [ 2, %bb1 ], [ %tmp6, %bb9 ]
%tmp6 = add nuw nsw i32 %tmp, 1
%tmp7 = icmp ult i32 %tmp6, undef
br i1 %tmp7, label %bb13, label %bb18
bb8: ; preds = %bb8
br label %bb8
bb9: ; No predecessors!
br label %bb5
bb10: ; preds = %bb10
br label %bb10
bb11: ; preds = %bb11
br label %bb11
bb12: ; preds = %bb12
br label %bb12
bb13: ; preds = %bb5
br label %bb14
bb14: ; preds = %bb14, %bb13
%tmp15 = phi i32 [ %tmp16, %bb14 ], [ undef, %bb13 ]
%tmp16 = add nsw i32 %tmp15, 1
%tmp17 = icmp sgt i32 %tmp16, 25
br i1 %tmp17, label %bb19, label %bb14
bb18: ; preds = %bb5
unreachable
bb19: ; preds = %bb14
ret void
}
Offending patch:
commit ae7b1e8823a51068cfa64875fc5222e5b1d16760
Author: Philip Reames <<a href="mailto:listmail@philipreames.com">listmail@philipreames.com</a>>
Date: Wed Mar 31 10:29:21 2021 -0700
[SCEV] Handle unreachable binop when matching shift recurrence
This fixes an issue introduced with my change d4648e, and reported in
pr49768.
The root problem is that dominance collapses in unreachable code, and that
LoopInfo explicitly only models reachable code. Since the recurrence matcher
doesn't filter by reachability (and can't easily because not all consumers have
domtree), we need to bailout before assuming that finding a recurrence implies
we found a loop.</pre>
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