| Issue |
170024
|
| Summary |
clang: ICE in X86 DAG->DAG Instruction Selection when using inline assembly with 512-bit vector types and 'xchg' instruction
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
AbyssStaror
|
### Link for quick verification: https://godbolt.org/z/o4fW3sKjT (crash both on C and C++)
```c
typedef __int128 __attribute__((__vector_size__(64))) V;
void swap(V *a, V *b) {
// Induce xchg-like behavior using inline assembly to trigger register swaps.
asm volatile(
"xchg %[regA], %[regB]"
: [regA] "+r" (*a), [regB] "+r" (*b)
:
: "memory");
}
```
When compiling code that uses inline assembly with the 'xchg' instruction operating on 512-bit vector types (defined as
`__int128 __attribute__((__vector_size__(64))))`, the LLVM compiler crashes with an internal compiler error during the X86 DAG->DAG instruction selection phase.
## The stack dump:
```
0. Program arguments: /workspace/install/llvm/build_21.1.4/bin/clang-21 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name 2327.fuzz -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/workspace -fcoverage-compilation-dir=/workspace -resource-dir /workspace/install/llvm/build_21.1.4/lib/clang/21 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/x86_64-linux-gnu/c++/13 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/backward -internal-isystem /workspace/install/llvm/build_21.1.4/lib/clang/21/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -ferror-limit 19 -fmessage-length=190 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/2327-00d403.o -x c++ /workspace/exps/featurefuzz/generate_feature_fine_tuning_qwen_4b_input_2_feature_1_exp/cases/2327.fuzz
1. <eof> parser at end of file
2. Code generation
3. Running pass 'Function Pass Manager' on module '/workspace/exps/featurefuzz/generate_feature_fine_tuning_qwen_4b_input_2_feature_1_exp/cases/2327.fuzz'.
4. Running pass 'X86 DAG->DAG Instruction Selection' on function '@_Z4swapPDv4_nS0_'
#0 0x0000646f80099c2a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x9691c2a)
#1 0x0000646f8009a457 PrintStackTraceSignalHandler(void*) Signals.cpp:0:0
#2 0x0000646f80093f57 llvm::sys::RunSignalHandlers() (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x968bf57)
#3 0x0000646f800941c7 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#4 0x00007303e9f62330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#5 0x00007303e9fbbb2c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#6 0x00007303e9fbbb2c __pthread_kill_internal ./nptl/pthread_kill.c:78:10
#7 0x00007303e9fbbb2c pthread_kill ./nptl/pthread_kill.c:89:10
#8 0x00007303e9f6227e raise ./signal/../sysdeps/posix/raise.c:27:6
#9 0x00007303e9f458ff abort ./stdlib/abort.c:81:7
#10 0x00007303e9f4581b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#11 0x00007303e9f58517 (/lib/x86_64-linux-gnu/libc.so.6+0x3b517)
#12 0x0000646f82050866 llvm::TargetLowering::ParseConstraints(llvm::DataLayout const&, llvm::TargetRegisterInfo const*, llvm::CallBase const&) const (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xb648866)
#13 0x0000646f81e0c566 llvm::FunctionLoweringInfo::set(llvm::Function const&, llvm::MachineFunction&, llvm::SelectionDAG*) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xb404566)
#14 0x0000646f81fd5056 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xb5cd056)
#15 0x0000646f7ddf8c0c (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) X86ISelDAGToDAG.cpp:0:0
#16 0x0000646f81fbf38d llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xb5b738d)
#17 0x0000646f7ebbc586 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x81b4586)
#18 0x0000646f7f5b66a9 llvm::FPPassManager::runOnFunction(llvm::Function&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x8bae6a9)
#19 0x0000646f7f5b6e89 llvm::FPPassManager::runOnModule(llvm::Module&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x8baee89)
#20 0x0000646f7f5b5b77 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x8badb77)
#21 0x0000646f7f5b6469 llvm::legacy::PassManager::run(llvm::Module&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x8bae469)
#22 0x0000646f804c549e clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, 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*) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x9abd49e)
#23 0x0000646f80eae3a2 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xa4a63a2)
#24 0x0000646f83579eb5 clang::ParseAST(clang::Sema&, bool, bool) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xcb71eb5)
#25 0x0000646f812c192b clang::ASTFrontendAction::ExecuteAction() (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xa8b992b)
#26 0x0000646f80eaf360 clang::CodeGenAction::ExecuteAction() (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xa4a7360)
#27 0x0000646f812c99cf clang::FrontendAction::Execute() (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xa8c19cf)
#28 0x0000646f8120ff46 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xa807f46)
#29 0x0000646f81451f7b clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0xaa49f7b)
#30 0x0000646f7b1c0523 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x47b8523)
#31 0x0000646f7b1b0c58 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#32 0x0000646f7b1b6b28 clang_main(int, char**, llvm::ToolContext const&) (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x47aeb28)
#33 0x0000646f7b011b4a main (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x4609b4a)
#34 0x00007303e9f471ca __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#35 0x00007303e9f4728b call_init ./csu/../csu/libc-start.c:128:20
#36 0x00007303e9f4728b __libc_start_main ./csu/../csu/libc-start.c:347:5
#37 0x0000646f7b1aef55 _start (/workspace/install/llvm/build_21.1.4/bin/clang-21+0x47a6f55)
clang++: error: unable to execute command: Aborted (core dumped)
```
## The Clang version:
```
clang version 21.1.4 (https://github.com/llvm/llvm-project.git 222fc11f2b8f25f6a0f4976272ef1bb7bf49521d)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /workspace/install/llvm/build_21.1.4/bin
Build config: +assertions
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/13
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/13
Candidate multilib: .;@m64
Selected multilib: .;@m64
```
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