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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 - Optimized code debug info: loop induction variable becomes constant"
href="https://bugs.llvm.org/show_bug.cgi?id=35015">35015</a>
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<th>Summary</th>
<td>Optimized code debug info: loop induction variable becomes constant
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>aprantl@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Here's an example where loop optimizations cause very misleading debug info:
use(int i);
static struct status {
int value;
unsigned char *p;
} status[32];
int init(void)
{
int i;
for (i = 0; i < 32; i++) {
status[i].value = 42;
use(i);
}
}
clang -g -c test.i -o - -Oz | llvm-dwarfdump -name i -
0x0000009f: DW_TAG_variable [11]
DW_AT_location( 0x00000000
0x0000000000000010 - 0x0000000000000032: consts +0,
stack-value )
DW_AT_name( "i" )
DW_AT_type( {0x0000006c} ( int ) )
The output of -print-after-all should give us a hint at which pass(es) are
dropping the llvm.dbg.value. Perhaps this is a use-case for
llvm::salvageDebugInfo().</pre>
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</p>
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