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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 --- - ARM64 debug info empty prologue" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D24117&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=azGrfirESxTzLgFlrbFkZceA7wM4YHPh5hbBtXza0aE&s=vrw2PjRY1XHQs4CAPnju13Do4sfFmYVKeQMsYzHz1U8&e=">24117</a>
</td>
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<th>Summary</th>
<td>ARM64 debug info empty prologue
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>DebugInfo
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>kuba.brecka@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I'm seeing a regression in generated debug line information for ARM64 with -O1,
on Darwin. Consider this simple C source:
$ cat ditest.c
#include <stdlib.h>
int main() {
char *x = (char*)malloc(10 * sizeof(char));
return x[5];
}
If I compile this with LLVM 3.6.0, and then ask `atos` to retrieve the source
line for the `malloc` call instruction, it correctly says that it's line 3:
$ ~/llvm-3.6.0/bin/clang ditest.c -o ditest -arch arm64 -g -O1
$ otool -tv ditest
ditest:
(__TEXT,__text) section
_main:
0000000100007f6c stp x29, x30, [sp, #-16]!
0000000100007f70 mov x29, sp
0000000100007f74 movz w0, #0xa
0000000100007f78 bl 0x100007f88 ; symbol stub for: _malloc
0000000100007f7c ldrsb w0, [x0, #5]
0000000100007f80 ldp x29, x30, [sp], #16
0000000100007f84 ret
$ atos -o ditest 0000000100007f78
main (in ditest) (ditest.c:3)
However, if I do the same with current LLVM trunk, `atos` says the same
instruction has source line number 2:
$ ~/llvm-trunk/bin/clang ditest.c -o ditest -arch arm64 -g -O1
$ otool -tv ditest
ditest:
(__TEXT,__text) section
_main:
0000000100007f6c stp x29, x30, [sp, #-16]!
0000000100007f70 mov x29, sp
0000000100007f74 movz w0, #0xa
0000000100007f78 bl 0x100007f88 ; symbol stub for: _malloc
0000000100007f7c ldrsb w0, [x0, #5]
0000000100007f80 ldp x29, x30, [sp], #16
0000000100007f84 ret
$ atos -o ditest 0000000100007f78
main (in ditest) (ditest.c:2)
The difference in the DWARF line info is in the way how the end of prologue is
marked, current LLVM trunk emits:
$ dwarfdump --debug-line ditest.dSYM/Contents/Resources/DWARF/ditest
...
0x0000002b: DW_LNE_set_address( 0x0000000100007f6c )
0x00000036: address += 0, line += 1
0x0000000100007f6c 1 2 0 is_stmt
0x00000037: DW_LNS_set_column( 20 )
0x00000039: DW_LNS_set_prologue_end
0x0000003a: address += 0, line += 1
0x0000000100007f6c 1 3 20 is_stmt prologue_end
Where it looks like the `address += 0` indicates that the prologue of the
function is empty, which isn't true. The generated line information then
contains a duplicate definition for address `0x0000000100007f6c`, I don't know
if that's valid or not.</pre>
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