clang: 18: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.

[wierton]

When compile this program with clang 18, clang 18 assertion fails, while clang 17 compiles it without any issues..

void f(unsigned char *a) {
  int ret;
  asm volatile("setb %0 %1" : "=r"(ret) : "r"(a));
}

Compiler Explorer: https://gcc.godbolt.org/z/G664rETEz

The crash output:

clang: /root/llvm-project/llvm/include/llvm/Support/Casting.h:578: decltype(auto) llvm::cast(From*) [with To = llvm::MCTargetExpr; From = const llvm::MCExpr]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang -gdwarf-4 -g -o /app/output.s -S --gcc-toolchain=/opt/compiler-explorer/gcc-9.2.0 -fcolor-diagnostics -fno-crash-diagnostics -O0 <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 Assembly Printer' on function '@f'
 #0 0x00000000037619f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x37619f8)
 #1 0x000000000375f6dc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x375f6dc)
 #2 0x00000000036a8248 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007fc2c93bb420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007fc2c8e7e00b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #5 0x00007fc2c8e5d859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #6 0x00007fc2c8e5d729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #7 0x00007fc2c8e6efd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x00000000034548df llvm::MCExpr::evaluateAsRelocatableImpl(llvm::MCValue&, llvm::MCAssembler const*, llvm::MCAsmLayout const*, llvm::MCFixup const*, llvm::DenseMap<llvm::MCSection const*, unsigned long, llvm::DenseMapInfo<llvm::MCSection const*, void>, llvm::detail::DenseMapPair<llvm::MCSection const*, unsigned long>> const*, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x34548df)
 #9 0x0000000003454b38 llvm::MCExpr::evaluateAsAbsolute(long&) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3454b38)
#10 0x00000000034e8adb (anonymous namespace)::AsmParser::parseExpression(llvm::MCExpr const*&, llvm::SMLoc&) (.part.0) AsmParser.cpp:0:0
#11 0x00000000025febf6 (anonymous namespace)::X86AsmParser::parseATTOperand(llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>>&) X86AsmParser.cpp:0:0
#12 0x0000000002603ae1 (anonymous namespace)::X86AsmParser::ParseInstruction(llvm::ParseInstructionInfo&, llvm::StringRef, llvm::SMLoc, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>>&) X86AsmParser.cpp:0:0
#13 0x00000000034e12d2 (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) AsmParser.cpp:0:0
#14 0x00000000034fa327 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) (.part.0) AsmParser.cpp:0:0
#15 0x00000000034eeb85 (anonymous namespace)::AsmParser::Run(bool, bool) AsmParser.cpp:0:0
#16 0x00000000045dfcda llvm::AsmPrinter::emitInlineAsm(llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::MCTargetOptions const&, llvm::MDNode const*, llvm::InlineAsm::AsmDialect) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45dfcda)
#17 0x00000000045e0b99 llvm::AsmPrinter::emitInlineAsm(llvm::MachineInstr const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45e0b99)
#18 0x00000000045dbed0 llvm::AsmPrinter::emitFunctionBody() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45dbed0)
#19 0x0000000002270661 llvm::X86AsmPrinter::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x2270661)
#20 0x0000000002b5ffe1 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#21 0x000000000311a409 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311a409)
#22 0x000000000311a641 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311a641)
#23 0x000000000311ae82 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311ae82)
#24 0x00000000039d7046 (anonymous namespace)::EmitAssemblyHelper::EmitAssembly(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) BackendUtil.cpp:0:0
#25 0x00000000039d73d1 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x39d73d1)
#26 0x0000000003fe10c8 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe10c8)
#27 0x0000000005efcf09 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5efcf09)
#28 0x0000000003fe05e8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe05e8)
#29 0x0000000004246f89 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4246f89)
#30 0x00000000041c74ae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x41c74ae)
#31 0x000000000432653e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x432653e)
#32 0x0000000000bfd846 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbfd846)
#33 0x0000000000bf510a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#34 0x0000000004021909 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#35 0x00000000036a86f4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x36a86f4)
#36 0x0000000004021eff clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#37 0x0000000003fe9e75 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe9e75)
#38 0x0000000003fea8dd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fea8dd)
#39 0x0000000003ff2805 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3ff2805)
#40 0x0000000000bfacec clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbfacec)
#41 0x0000000000af4381 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xaf4381)
#42 0x00007fc2c8e5f083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#43 0x0000000000bf4bee _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbf4bee)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: wt.cc (wierton)

When compile this program with clang 18, clang 18 assertion fails, while clang 17 compiles it without any issues.. ``` void f(unsigned char *a) { int ret; asm volatile("setb %0 %1" : "=r"(ret) : "r"(a)); } ```

Compiler Explorer: https://gcc.godbolt.org/z/G664rETEz

The crash output:

clang: /root/llvm-project/llvm/include/llvm/Support/Casting.h:578: decltype(auto) llvm::cast(From*) [with To = llvm::MCTargetExpr; From = const llvm::MCExpr]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang -gdwarf-4 -g -o /app/output.s -S --gcc-toolchain=/opt/compiler-explorer/gcc-9.2.0 -fcolor-diagnostics -fno-crash-diagnostics -O0 <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 Assembly Printer' on function '@<!-- -->f'
 #<!-- -->0 0x00000000037619f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x37619f8)
 #<!-- -->1 0x000000000375f6dc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x375f6dc)
 #<!-- -->2 0x00000000036a8248 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x00007fc2c93bb420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #<!-- -->4 0x00007fc2c8e7e00b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #<!-- -->5 0x00007fc2c8e5d859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #<!-- -->6 0x00007fc2c8e5d729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #<!-- -->7 0x00007fc2c8e6efd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #<!-- -->8 0x00000000034548df llvm::MCExpr::evaluateAsRelocatableImpl(llvm::MCValue&amp;, llvm::MCAssembler const*, llvm::MCAsmLayout const*, llvm::MCFixup const*, llvm::DenseMap&lt;llvm::MCSection const*, unsigned long, llvm::DenseMapInfo&lt;llvm::MCSection const*, void&gt;, llvm::detail::DenseMapPair&lt;llvm::MCSection const*, unsigned long&gt;&gt; const*, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x34548df)
 #<!-- -->9 0x0000000003454b38 llvm::MCExpr::evaluateAsAbsolute(long&amp;) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3454b38)
#<!-- -->10 0x00000000034e8adb (anonymous namespace)::AsmParser::parseExpression(llvm::MCExpr const*&amp;, llvm::SMLoc&amp;) (.part.0) AsmParser.cpp:0:0
#<!-- -->11 0x00000000025febf6 (anonymous namespace)::X86AsmParser::parseATTOperand(llvm::SmallVectorImpl&lt;std::unique_ptr&lt;llvm::MCParsedAsmOperand, std::default_delete&lt;llvm::MCParsedAsmOperand&gt;&gt;&gt;&amp;) X86AsmParser.cpp:0:0
#<!-- -->12 0x0000000002603ae1 (anonymous namespace)::X86AsmParser::ParseInstruction(llvm::ParseInstructionInfo&amp;, llvm::StringRef, llvm::SMLoc, llvm::SmallVectorImpl&lt;std::unique_ptr&lt;llvm::MCParsedAsmOperand, std::default_delete&lt;llvm::MCParsedAsmOperand&gt;&gt;&gt;&amp;) X86AsmParser.cpp:0:0
#<!-- -->13 0x00000000034e12d2 (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&amp;, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) AsmParser.cpp:0:0
#<!-- -->14 0x00000000034fa327 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&amp;, llvm::MCAsmParserSemaCallback*) (.part.0) AsmParser.cpp:0:0
#<!-- -->15 0x00000000034eeb85 (anonymous namespace)::AsmParser::Run(bool, bool) AsmParser.cpp:0:0
#<!-- -->16 0x00000000045dfcda llvm::AsmPrinter::emitInlineAsm(llvm::StringRef, llvm::MCSubtargetInfo const&amp;, llvm::MCTargetOptions const&amp;, llvm::MDNode const*, llvm::InlineAsm::AsmDialect) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45dfcda)
#<!-- -->17 0x00000000045e0b99 llvm::AsmPrinter::emitInlineAsm(llvm::MachineInstr const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45e0b99)
#<!-- -->18 0x00000000045dbed0 llvm::AsmPrinter::emitFunctionBody() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x45dbed0)
#<!-- -->19 0x0000000002270661 llvm::X86AsmPrinter::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x2270661)
#<!-- -->20 0x0000000002b5ffe1 llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (.part.0) MachineFunctionPass.cpp:0:0
#<!-- -->21 0x000000000311a409 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311a409)
#<!-- -->22 0x000000000311a641 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311a641)
#<!-- -->23 0x000000000311ae82 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x311ae82)
#<!-- -->24 0x00000000039d7046 (anonymous namespace)::EmitAssemblyHelper::EmitAssembly(clang::BackendAction, std::unique_ptr&lt;llvm::raw_pwrite_stream, std::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;, clang::BackendConsumer*) BackendUtil.cpp:0:0
#<!-- -->25 0x00000000039d73d1 clang::EmitBackendOutput(clang::DiagnosticsEngine&amp;, clang::HeaderSearchOptions const&amp;, clang::CodeGenOptions const&amp;, clang::TargetOptions const&amp;, clang::LangOptions const&amp;, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::unique_ptr&lt;llvm::raw_pwrite_stream, std::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;, clang::BackendConsumer*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x39d73d1)
#<!-- -->26 0x0000000003fe10c8 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe10c8)
#<!-- -->27 0x0000000005efcf09 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5efcf09)
#<!-- -->28 0x0000000003fe05e8 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe05e8)
#<!-- -->29 0x0000000004246f89 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4246f89)
#<!-- -->30 0x00000000041c74ae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x41c74ae)
#<!-- -->31 0x000000000432653e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x432653e)
#<!-- -->32 0x0000000000bfd846 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbfd846)
#<!-- -->33 0x0000000000bf510a ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->34 0x0000000004021909 void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const::'lambda'()&gt;(long) Job.cpp:0:0
#<!-- -->35 0x00000000036a86f4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x36a86f4)
#<!-- -->36 0x0000000004021eff clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (.part.0) Job.cpp:0:0
#<!-- -->37 0x0000000003fe9e75 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fe9e75)
#<!-- -->38 0x0000000003fea8dd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fea8dd)
#<!-- -->39 0x0000000003ff2805 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3ff2805)
#<!-- -->40 0x0000000000bfacec clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbfacec)
#<!-- -->41 0x0000000000af4381 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xaf4381)
#<!-- -->42 0x00007fc2c8e5f083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#<!-- -->43 0x0000000000bf4bee _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbf4bee)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[shafik]

Confirmed

[cygao90]

Maybe godbolt's clang-17 didn't enable assertion. I compiled debug version of clang-17.0.1 and it fails too.

[phoebewang]

Maybe godbolt's clang-17 didn't enable assertion. I compiled debug version of clang-17.0.1 and it fails too.

It's true, the assertion fail persisted since clang-8: https://godbolt.org/z/4rEa78vz9

[phoebewang]

Generally, it is a misuse of inline assembly, GCC cannot compile it too: https://godbolt.org/z/8zc8G1WTv
There are two problems in the assembly:

• setb only supports one operand.
• The return type doesn't match with operand size.

The correct form would be

void f(unsigned char *a) {
  char ret;
  asm volatile("setb %0" : "=r"(ret) : "r"(a));
}

Nevertheless, it (arguably) is Clang's problem that doesn't detect the illegal case and report error in advance.