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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 - __attribute__((naked)) function loses parameter"
href="https://bugs.llvm.org/show_bug.cgi?id=36078">36078</a>
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<th>Summary</th>
<td>__attribute__((naked)) function loses parameter
</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>Linux
</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>Interprocedural Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>momchil.velikov@arm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=19740" name="attach_19740" title="minimal testcase">attachment 19740</a> <a href="attachment.cgi?id=19740&action=edit" title="minimal testcase">[details]</a></span>
minimal testcase
LLVM discards a parameter of a function, declared with the "naked" attribute.
Compiling the attached test program for Arm with `clang -target arm-eabi -O3 -S
naked.c` output the following assembly for `bar`:
bar:
.fnstart
b foo
i.e. the parameter to `foo` is not passed at all.
This change occurs during "Deduce function attributes", which marks the
parameter with "readnone" and subsequently it's removed by "Promote 'by
reference' arguments to scalars" pass.
*** IR Dump After Function Integration/Inlining ***
; Function Attrs: naked noinline nounwind
define internal fastcc i32 @foo(i32*) unnamed_addr #1 {
entry:
call void asm sideeffect "ldr r0, [r0] \0Abx lr \0A", ""() #2,
!srcloc !3
unreachable
}
*** IR Dump After Deduce function attributes ***
; Function Attrs: naked noinline nounwind
define internal fastcc i32 @foo(i32* nocapture readnone) unnamed_addr #1 {
entry:
call void asm sideeffect "ldr r0, [r0] \0Abx lr \0A", ""() #2,
!srcloc !3
unreachable
}
*** IR Dump After Promote 'by reference' arguments to scalars ***
; Function Attrs: naked noinline nounwind
define internal fastcc i32 @foo() unnamed_addr #1 {
entry:
call void asm sideeffect "ldr r0, [r0] \0Abx lr \0A", ""() #2,
!srcloc !3
unreachable
}</pre>
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