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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 - 7.1 2.2 Example does not work properly after disabling -fmerge-all-constants"
href="https://bugs.llvm.org/show_bug.cgi?id=37058">37058</a>
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<th>Summary</th>
<td>7.1 2.2 Example does not work properly after disabling -fmerge-all-constants
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ilia.taraban@intel.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>This test starts failing after disabling -fmerge-all-constants:
================= nice.cpp ============
const char * goo (const char * s1, const char * s2)
{
const char * p;
if (* s2 == '\0')
return 0;
p = 0;
return 0;
}
void foo (const char * s)
{
const char * p = goo(0, "S");
int i;
}
struct S { int n; };
auto f ()
{
S x = { 1 };
constexpr S y = { 2 };
return [&](bool b) { return (b ? y : x).n;
};
}
auto g = f();
int main (int argc, char * argv [])
{
foo(0);
int n = g(true); // OK, according to 7.1 2.2
return 2 - n;
}
=======================================
<span class="quote">>>> clang -v</span >
clang version 7.0.0 (trunk 329586)
Target: x86_64-unknown-linux-gnu
Thread model: posix
...
<span class="quote">>>> clang++ -o nice.exe nice.cpp
>>> nice.exe</span >
2
<span class="quote">>>> clang++ -o nice.exe nice.cpp -fmerge-all-constants
>>> nice.exe</span >
0
So after disabling this option current test (which is similar to Example from
7.1 2.2) giving wrong result. Now x and y behave similar.
<span class="quote">>>> @_ZZ3maxvE1a = private unnamed_addr constant %struct.A { i32 1 }, align 4
>>> @_ZZ3maxvE1b = private unnamed_addr constant %struct.A { i32 2 }, align 4</span ></pre>
</div>
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