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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed opportunity to emit call site parameter entry"
href="https://bugs.llvm.org/show_bug.cgi?id=44119">44119</a>
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<th>Summary</th>
<td>Missed opportunity to emit call site parameter entry
</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>
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<th>OS</th>
<td>Windows NT
</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>david.stenberg@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
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<pre>Reproduced on 3889ff82bf4057ead22dad91a89384ac20ebd557.
Compiling the following file:
extern void callee(int);
extern int value(void);
extern int global;
int caller() {
if (global) {
int local = value();
callee(local);
return local;
}
return 0;
}
using:
clang --target=x86_64 -O1 -g -Xclang -femit-debug-entry-values -c missed.c
we do not get a call site parameter entry for callee's parameter:
llvm-dwarfdump missed.o | grep -c call_site_parameter
0
This is the code for the call and the parameter value:
CALL64pcrel32 @value, csr_64, implicit $rsp, implicit $ssp, implicit-def
$rsp, implicit-def $ssp, implicit-def $eax, debug-location !26
$ebx = MOV32rr $eax, debug-location !26
DBG_VALUE $ebx, $noreg, !17, !DIExpression(), debug-location !27
$edi = MOV32rr $eax, debug-location !28
CALL64pcrel32 @callee, csr_64, implicit $rsp, implicit $ssp, implicit killed
$edi, implicit-def $rsp, implicit-def $ssp, debug-location !28
JMP_1 %bb.3
The describeLoadedValue() hook will be able to describe that the value of $edi
is available in $eax, but as that is not a preserved register we can't emit a
call site entry using that. The code does not understand that $eax's value is
available in the preserved register $ebx during the call. When looking for call
site values in collectCallSiteParameters(), should we also keep track of other
copy instructions, and then try to find a preserved copy of the register to
instead describe the call site entry with?</pre>
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