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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - allow indicating that calls to asm expressions are [[noreturn]]"
href="https://bugs.llvm.org/show_bug.cgi?id=50449">50449</a>
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<th>Summary</th>
<td>allow indicating that calls to asm expressions are [[noreturn]]
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>gonzalo.gadeschi@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Example (minimized): <a href="https://gcc.godbolt.org/z/nqKq49q7a">https://gcc.godbolt.org/z/nqKq49q7a</a>
[[noreturn]] void trap() {
asm volatile ("ret");
}
generates this LLVM-IR:
define dso_local void @_Z4trapv() #0 {
call void asm sideeffect "ret", "~{dirflag},~{fpsr},~{flags}"() #1,
!srcloc !4
ret void
}
attributes #0 = { noinline noreturn nounwind optnone uwtable mustprogress }
attributes #1 = { nounwind }
and there does not appear to be a way to add the LLVM-IR "noreturn" attribute
to the call such that #1 becomes:
attributes #1 = { nounwind noreturn }
There are a couple of ways in which this could be allowed, e.g.,:
- supporting: [[noreturn]] asm volatile(....)
- supporting: asm volatile(... : : : "noreturn")
If this is supported, both the LLVM-IR "call" or "invoke" instructions
generated should have the "noreturn" attribute.
Also, the warning produced:
warning: function declared 'noreturn' should not return
[-Winvalid-noreturn]
should probably be updated to take inline asm expressions that never return
into account.</pre>
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