llvm::DominatorTreeBase::recalculate called on empty function with if-converter #167419
Description
Repro
define i32 @sext_known_nonzero(i16 %xx) { %x = shl i16 256, %xx %z = sext i16 %x to i32 %r = call i32 @llvm.cttz.i32(i32 %z, i1 false) ret i32 %r }$ llc -start-before=if-converter test.ll
:DomTreeBuilder::SemiNCAInfo<llvm::DominatorTreeBase<llvm::MachineBasicBlock, false> >::InfoRec; <template-parameter-1-2> = void; reference = llvm::DomTreeBuilder::SemiNCAInfo<llvm::DominatorTreeBase<llvm::MachineBasicBlock, false> >::InfoRec&; size_type = long unsigned int]: Assertion `idx < size()' failed. PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug. Stack dump: 0. Program arguments: ./bin/llc a.ll -start-before=if-converter -print-after-all 1. Running pass 'Function Pass Manager' on module 'a.ll'. 2. Running pass 'X86 Assembly Printer' on function '@sext_known_nonzero' Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it): 0 llc 0x000055784892fdf6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 59 1 llc 0x00005578489302ba 2 llc 0x000055784892d892 llvm::sys::RunSignalHandlers() + 131 3 llc 0x000055784892f75f 4 libc.so.6 0x00007f9077449df0 5 libc.so.6 0x00007f907749e95c 6 libc.so.6 0x00007f9077449cc2 gsignal + 18 7 libc.so.6 0x00007f90774324ac abort + 34 8 libc.so.6 0x00007f9077432420 __assert_perror_fail + 0 9 llc 0x000055784729b6f0 10 llc 0x0000557847297e83 11 llc 0x00005578472999a8 12 llc 0x00005578472953be 13 llc 0x00005578472918db 14 llc 0x000055784728fc3c void llvm::DomTreeBuilder::Calculate<llvm::DominatorTreeBase<llvm::MachineBasicBlock, false>>(llvm::DominatorTreeBase<llvm::MachineBasicBlock, false>&) + 29 15 llc 0x000055784728f922 llvm::DominatorTreeBase<llvm::MachineBasicBlock, false>::recalculate(llvm::MachineFunction&) + 52 16 llc 0x0000557846e34e68 llvm::AsmPrinter::emitFunctionBody() + 292 17 llc 0x0000557845b5c481 18 llc 0x00005578472cdbbb llvm::MachineFunctionPass::runOnFunction(llvm::Function&) + 1117 19 llc 0x0000557847b5a06b llvm::FPPassManager::runOnFunction(llvm::Function&) + 639 20 llc 0x0000557847b5a2cd llvm::FPPassManager::runOnModule(llvm::Module&) + 97 21 llc 0x0000557847b5a6d8 22 llc 0x0000557847b55f22 llvm::legacy::PassManagerImpl::run(llvm::Module&) + 244 23 llc 0x0000557847b5af03 llvm::legacy::PassManager::run(llvm::Module&) + 39