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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - incorrect code generated when adding 64-bit constant to 64-bit variable"
href="https://llvm.org/bugs/show_bug.cgi?id=28544">28544</a>
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<th>Summary</th>
<td>incorrect code generated when adding 64-bit constant to 64-bit variable
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</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>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>markv@sassafras.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16738" name="attach_16738" title="C source demonstrating the bug">attachment 16738</a> <a href="attachment.cgi?id=16738&action=edit" title="C source demonstrating the bug">[details]</a></span>
C source demonstrating the bug
Adding a 64-bit constant value to a 64-bit referenced value generates incorrect
code when clang runs with -O1 or higher. The test case is very simple:
void
f1 (unsigned long long *foo)
{
*foo += 0x0000000800000000LL;
}
I compile thing with a command like the following:
clang -S -O1 test.c
Generated code looks like this (abridged):
pushq %rbp
movq %rsp, %rbp
subq $-2147483648, (%rdi) ## imm = 0xFFFFFFFF80000000
popq %rbp
retq
For reference, similar code is compiled correctly:
unsigned long long
f2 (unsigned long long foo)
{
return(foo + 0x0000000800000000LL);
}
Results in:
pushq %rbp
movq %rsp, %rbp
movabsq $34359738368, %rax ## imm = 0x800000000
addq %rdi, %rax
popq %rbp
retq
Attached file .c has these two routines.</pre>
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