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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - instCombine: incorrect fold of pointer comparison between globals"
href="https://bugs.llvm.org/show_bug.cgi?id=50208">50208</a>
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<th>Summary</th>
<td>instCombine: incorrect fold of pointer comparison between globals
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>miscompilation
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
<tr>
<th>Reporter</th>
<td>nunoplopes@sapo.pt
</td>
</tr>
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<th>CC</th>
<td>juneyoung.lee@sf.snu.ac.kr, llvm-bugs@lists.llvm.org, nikita.ppv@gmail.com, spatel+llvm@rotateright.com
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<pre>test: Transforms/InstSimplify/ConstProp/icmp-null.ll
The transformation below is only correct if the gep is over i8*, and not with
non-byte-sized types. This is correct: <a href="https://alive2.llvm.org/ce/z/S_TsHW">https://alive2.llvm.org/ce/z/S_TsHW</a>
----------------------------------------
@g2 = global 4 bytes, align 4
@g = global 8 bytes, align 4
define i1 @null_gep_ne_global() {
%__constexpr_0 = ptrtoint * @g2 to i64
%gep = gep * null, 8 x i64 %__constexpr_0 ; <-- notice the 8 x
%cmp = icmp ne * %gep, @g
ret i1 %cmp
}
=>
@g2 = global 4 bytes, align 4
@g = global 8 bytes, align 4
define i1 @null_gep_ne_global() {
ret i1 1
}
Transformation doesn't verify!
ERROR: Value mismatch
Example:
Source:
i64 %__constexpr_0 = #x924925b6db6f5564 (10540997870133138788,
-7905746203576412828)
* %gep = pointer(non-local, block_id=0, offset=-7905737407482647776)
i1 %cmp = #x0 (0)
SOURCE MEMORY STATE
===================
NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 1 alloc type: 0 address: 0
Block 1 > size: 4 align: 4 alloc type: 0 address:
10540997870133138788
Block 2 > size: 8 align: 4 alloc type: 0 address:
10541006666226903840
Target:
Source value: #x0 (0)
Target value: #x1 (1)</pre>
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