Large _BitInt constant leads to clang crash #162322
Description
In clang 21.1.0 and in CE's "trunk" as of today, the following program leads to a crash (https://gcc.godbolt.org/z/8s3zGxf6q ):
#include <stdio.h>
#include <fenv.h>
int main(void) {
// Enable access to the floating-point environment
#pragma STDC FENV_ACCESS ON
// Set rounding mode to downward (toward -∞)
if (fesetround(FE_DOWNWARD) != 0) {
perror("Failed to set rounding mode");
return 1;
}
double d = (double) 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999wb;
printf("Rounding mode set to downward.\n");
printf("Converted to double: %.17g\n", d);
}
Commandline options: -std=c23 -frounding-math -lm
Backtrace in "trunk":
fatal error: error in backend: unsupported library call operation
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-21.1.0/bin/clang -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-15.2.0 -fcolor-diagnostics -fno-crash-diagnostics -std=c23 -frounding-math -lm <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 '@main'
#0 0x0000000003bfa6c8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3bfa6c8)
#1 0x0000000003bf809c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3bf809c)
#2 0x0000000003b48913 llvm::CrashRecoveryContext::HandleExit(int) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3b48913)
#3 0x0000000003bef8ee llvm::sys::Process::Exit(int, bool) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3bef8ee)
#4 0x0000000000da3edb LLVMErrorHandler(void*, char const*, bool) cc1_main.cpp:0:0
#5 0x0000000003b52843 llvm::report_fatal_error(llvm::Twine const&, bool) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3b52843)
#6 0x0000000003b529d9 (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3b529d9)
#7 0x0000000005218e61 llvm::TargetLowering::makeLibCall(llvm::SelectionDAG&, llvm::RTLIB::Libcall, llvm::EVT, llvm::ArrayRef<llvm::SDValue>, llvm::TargetLowering::MakeLibCallOptions, llvm::SDLoc const&, llvm::SDValue) const (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x5218e61)
#8 0x00000000052fc154 llvm::DAGTypeLegalizer::ExpandIntOp_XINT_TO_FP(llvm::SDNode*) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x52fc154)
#9 0x00000000052fee78 llvm::DAGTypeLegalizer::ExpandIntegerOperand(llvm::SDNode*, unsigned int) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x52fee78)
#10 0x000000000523e5c9 llvm::DAGTypeLegalizer::run() (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x523e5c9)
#11 0x000000000523ea31 llvm::SelectionDAG::LegalizeTypes() (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x523ea31)
#12 0x00000000051ac3f2 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x51ac3f2)
#13 0x00000000051af546 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x51af546)
#14 0x00000000051b0d46 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x51b0d46)
#15 0x000000000519d7c1 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x519d7c1)
#16 0x0000000002fd6b0d llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x2fd6b0d)
#17 0x0000000003550fd2 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3550fd2)
#18 0x0000000003551261 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3551261)
#19 0x0000000003552ba9 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3552ba9)
#20 0x0000000003ea98f0 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*) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3ea98f0)
#21 0x000000000454906c clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x454906c)
#22 0x000000000618f19c clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x618f19c)
#23 0x000000000454985d clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x454985d)
#24 0x000000000485b83a clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x485b83a)
#25 0x00000000047d655b clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x47d655b)
#26 0x000000000494e513 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x494e513)
#27 0x0000000000da5f25 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0xda5f25)
#28 0x0000000000d9de2d ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#29 0x00000000045bb869 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
#30 0x0000000003b48813 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x3b48813)
#31 0x00000000045bba89 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
#32 0x000000000457eddd clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x457eddd)
#33 0x000000000457fd91 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x457fd91)
#34 0x000000000458d29c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0x458d29c)
#35 0x0000000000da2751 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-21.1.0/bin/clang+0xda2751)
#36 0x0000000000c526f4 main (/opt/compiler-explorer/clang-21.1.0/bin/clang+0xc526f4)
#37 0x00007a4a0ee29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#38 0x00007a4a0ee29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#39 0x0000000000d9d8c5 _start (/opt/compiler-explorer/clang-21.1.0/bin/clang+0xd9d8c5)
clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
Compiler returned: 70