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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Assertion failure with GVNHoist: Assertion `MSSA->dominates(NewDef, FirstDef) && "Should have dominated the new access"' failed."
href="https://bugs.llvm.org/show_bug.cgi?id=36484">36484</a>
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<th>Summary</th>
<td>Assertion failure with GVNHoist: Assertion `MSSA->dominates(NewDef, FirstDef) && "Should have dominated the new access"' failed.
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<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
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>efriedma@codeaurora.org
</td>
</tr>
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<th>CC</th>
<td>dberlin@dberlin.org, hiraditya@msn.com, llvm-bugs@lists.llvm.org
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<pre>Testcase (crashes with "opt -gvn-hoist"):
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
define void @f(i8* %p) {
entry:
switch i4 undef, label %if.then30 [
i4 4, label %if.end
i4 0, label %if.end
]
if.end:
br label %if.end19
if.end19:
br i1 undef, label %e, label %e.thread
e.thread:
store i8 0, i8* %p, align 4
br label %if.then30
if.then30:
call void @g()
unreachable
e:
store i8 0, i8* %p, align 4
unreachable
}
declare void @g()
--------------------------------------------------------------------
The issue is related to the MemoryPhi in the block if.then30.
MemorySSAUpdater::moveTo erases the store in the block e.thread, then erases
the MemoryPHI in if.then30 because it's trivial (temporarily), then tries to
insert a def in if.end19. fixupDefs then asserts that if.end19 dominates
if.then30, which is not true.
Not sure what the right fix is here.</pre>
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