Clang-20: fatal error: error in backend: Cannot select: intrinsic %llvm.bpf.load.half

[iamanonymouscs]

Description

I encountered a crash in Clang when compiling my source code with the following options:

-O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie  -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address 

These options together seem to trigger an internal error in the compiler, resulting in a backend crash. The issue occurs consistently with my project when options are used.

The issue can also be reproduced on Compiler Explorer.https://godbolt.org/z/4KPhqx7so

Code

repro-f3f3a4.zip

Command

clang repro-f3f3a4.c -O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie  -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address  -c -o repro-f3f3a4.o

Output

fatal error: error in backend: Cannot select: intrinsic %llvm.bpf.load.half
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 -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 DAG->DAG Instruction Selection' on function '@repro_main'
 #0 0x0000000003bd5b48 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bd5b48)
 #1 0x0000000003bd384c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bd384c)
 #2 0x0000000003b21746 llvm::CrashRecoveryContext::HandleExit(int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b21746)
 #3 0x0000000003bcab8e llvm::sys::Process::Exit(int, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bcab8e)
 #4 0x0000000000ce1100 LLVMErrorHandler(void*, char const*, bool) cc1_main.cpp:0:0
 #5 0x0000000003b2c7c3 llvm::report_fatal_error(llvm::Twine const&, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b2c7c3)
 #6 0x0000000004eb0a78 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb0a78)
 #7 0x0000000004eb66f9 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb66f9)
 #8 0x00000000026d59a1 (anonymous namespace)::X86DAGToDAGISel::Select(llvm::SDNode*) X86ISelDAGToDAG.cpp:0:0
 #9 0x0000000004ead86b llvm::SelectionDAGISel::DoInstructionSelection() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ead86b)
#10 0x0000000004ebc9f9 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ebc9f9)
#11 0x0000000004ebfac2 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ebfac2)
#12 0x0000000004ec0de0 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ec0de0)
#13 0x0000000004eb1b3f llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb1b3f)
#14 0x0000000002f3c849 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#15 0x0000000003539480 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3539480)
#16 0x0000000003539831 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3539831)
#17 0x000000000353a0e7 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x353a0e7)
#18 0x0000000003e83b15 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+0x3e83b15)
#19 0x000000000454b6ad clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x454b6ad)
#20 0x00000000066a031c clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x66a031c)
#21 0x000000000454ba98 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x454ba98)
#22 0x0000000004805949 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4805949)
#23 0x0000000004784bae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4784bae)
#24 0x00000000048eb0ee clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x48eb0ee)
#25 0x0000000000ce35ff cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xce35ff)
#26 0x0000000000cdb2ca ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#27 0x000000000458f029 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
#28 0x0000000003b21684 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b21684)
#29 0x000000000458f61f 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
#30 0x000000000455564d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x455564d)
#31 0x000000000455673d 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+0x455673d)
#32 0x000000000455db25 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x455db25)
#33 0x0000000000ce04a9 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xce04a9)
#34 0x0000000000bae764 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbae764)
#35 0x00007116d2029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#36 0x00007116d2029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#37 0x0000000000cdad7e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xcdad7e)
clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
Compiler returned: 70

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Anonymous (iamanonymouscs)

### Description I encountered a crash in Clang when compiling my source code with the following options: ```sh -O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address ```

These options together seem to trigger an internal error in the compiler, resulting in a backend crash. The issue occurs consistently with my project when options are used.

The issue can also be reproduced on Compiler Explorer.https://godbolt.org/z/4KPhqx7so

Code

repro-f3f3a4.zip

Command

clang repro-f3f3a4.c -O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie  -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address  -c -o repro-f3f3a4.o

Output

fatal error: error in backend: Cannot select: intrinsic %llvm.bpf.load.half
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 -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -O3 -ffast-math -fdiscard-value-names -fsanitize-address-poison-custom-array-cookie -Wall -Wextra -fno-strict-aliasing -fwrapv -g -fsanitize=address <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 DAG-&gt;DAG Instruction Selection' on function '@<!-- -->repro_main'
 #<!-- -->0 0x0000000003bd5b48 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bd5b48)
 #<!-- -->1 0x0000000003bd384c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bd384c)
 #<!-- -->2 0x0000000003b21746 llvm::CrashRecoveryContext::HandleExit(int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b21746)
 #<!-- -->3 0x0000000003bcab8e llvm::sys::Process::Exit(int, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3bcab8e)
 #<!-- -->4 0x0000000000ce1100 LLVMErrorHandler(void*, char const*, bool) cc1_main.cpp:0:0
 #<!-- -->5 0x0000000003b2c7c3 llvm::report_fatal_error(llvm::Twine const&amp;, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b2c7c3)
 #<!-- -->6 0x0000000004eb0a78 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb0a78)
 #<!-- -->7 0x0000000004eb66f9 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb66f9)
 #<!-- -->8 0x00000000026d59a1 (anonymous namespace)::X86DAGToDAGISel::Select(llvm::SDNode*) X86ISelDAGToDAG.cpp:0:0
 #<!-- -->9 0x0000000004ead86b llvm::SelectionDAGISel::DoInstructionSelection() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ead86b)
#<!-- -->10 0x0000000004ebc9f9 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ebc9f9)
#<!-- -->11 0x0000000004ebfac2 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ebfac2)
#<!-- -->12 0x0000000004ec0de0 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4ec0de0)
#<!-- -->13 0x0000000004eb1b3f llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4eb1b3f)
#<!-- -->14 0x0000000002f3c849 llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (.part.0) MachineFunctionPass.cpp:0:0
#<!-- -->15 0x0000000003539480 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3539480)
#<!-- -->16 0x0000000003539831 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3539831)
#<!-- -->17 0x000000000353a0e7 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x353a0e7)
#<!-- -->18 0x0000000003e83b15 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+0x3e83b15)
#<!-- -->19 0x000000000454b6ad clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x454b6ad)
#<!-- -->20 0x00000000066a031c clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x66a031c)
#<!-- -->21 0x000000000454ba98 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x454ba98)
#<!-- -->22 0x0000000004805949 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4805949)
#<!-- -->23 0x0000000004784bae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4784bae)
#<!-- -->24 0x00000000048eb0ee clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x48eb0ee)
#<!-- -->25 0x0000000000ce35ff cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xce35ff)
#<!-- -->26 0x0000000000cdb2ca ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->27 0x000000000458f029 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
#<!-- -->28 0x0000000003b21684 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3b21684)
#<!-- -->29 0x000000000458f61f 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
#<!-- -->30 0x000000000455564d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x455564d)
#<!-- -->31 0x000000000455673d 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+0x455673d)
#<!-- -->32 0x000000000455db25 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+0x455db25)
#<!-- -->33 0x0000000000ce04a9 clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xce04a9)
#<!-- -->34 0x0000000000bae764 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbae764)
#<!-- -->35 0x00007116d2029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->36 0x00007116d2029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->37 0x0000000000cdad7e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xcdad7e)
clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
Compiler returned: 70

[yonghong-song]

The C code is for bpf and it contains bpf specific builtin function. Here your compilation is using x86 and it won't work since bpf specific builtin not recognized by x86 compiler. If you compile with bpf target and remove sanitize flag, the compilation should go through.