[llvm] [PHIElimination] Reuse existing COPY in predecessor basic block (PR #131837)

Sun Jun 29 12:26:01 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-multistage` running on `ppc64le-clang-multistage-test` while building `llvm` at step 10 "build stage 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/76/builds/10862

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 10 (build stage 2) failure: 'ninja' (failure)
...
[2413/6442] Building CXX object lib/Passes/CMakeFiles/LLVMPasses.dir/CodeGenPassBuilder.cpp.o
[2414/6442] Building CXX object lib/Transforms/Coroutines/CMakeFiles/LLVMCoroutines.dir/CoroSplit.cpp.o
[2415/6442] Building CXX object lib/IR/CMakeFiles/LLVMCore.dir/Dominators.cpp.o
[2416/6442] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/GlobalOpt.cpp.o
[2417/6442] Building CXX object lib/Passes/CMakeFiles/LLVMPasses.dir/PassBuilderBindings.cpp.o
[2418/6442] Building CXX object utils/TableGen/CMakeFiles/llvm-tblgen.dir/GlobalISelEmitter.cpp.o
[2419/6442] Building CXX object lib/Transforms/Scalar/CMakeFiles/LLVMScalarOpts.dir/LoopIdiomRecognize.cpp.o
[2420/6442] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineBasicBlock.cpp.o
[2421/6442] Building CXX object lib/Transforms/Scalar/CMakeFiles/LLVMScalarOpts.dir/ConstraintElimination.cpp.o
[2422/6442] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o 
ccache /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/clang++ -DGTEST_HAS_RTTI=0 -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17 -fPIC  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/lib/CodeGen/LiveDebugVariables.cpp
clang++: /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/include/llvm/CodeGen/Register.h:83: unsigned int llvm::Register::virtRegIndex() const: Assertion `isVirtual() && "Not a virtual register"' 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: /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/clang++ -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -std=c++17 -fPIC -fno-exceptions -funwind-tables -fno-rtti -DGTEST_HAS_RTTI=0 -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage2/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/include -DNDEBUG -UNDEBUG -c -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LiveDebugVariables.cpp.o /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/lib/CodeGen/LiveDebugVariables.cpp
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/llvm/lib/CodeGen/LiveDebugVariables.cpp'.
4.	Running pass 'Register Coalescer' on function '@_ZN4llvm18LiveDebugVariables7LDVImpl18collectDebugValuesERNS_15MachineFunctionEb'
 #0 0x00007fff8def6e40 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMSupport.so.21.0git+0x256e40)
 #1 0x00007fff8def4754 llvm::sys::CleanupOnSignal(unsigned long) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMSupport.so.21.0git+0x254754)
 #2 0x00007fff8dd95858 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007fff9bbe04d8 (linux-vdso64.so.1+0x4d8)
 #4 0x00007fff8d71a4c8 raise (/lib64/libc.so.6+0x4a4c8)
 #5 0x00007fff8d6f4a54 abort (/lib64/libc.so.6+0x24a54)
 #6 0x00007fff8d70dcb0 __assert_fail_base (/lib64/libc.so.6+0x3dcb0)
 #7 0x00007fff8d70dd54 __assert_fail (/lib64/libc.so.6+0x3dd54)
 #8 0x00007fff922a2154 llvm::VirtReg2IndexFunctor::operator()(llvm::Register) const (.isra.72.part.73) InlineSpiller.cpp:0:0
 #9 0x00007fff922a382c llvm::MachineRegisterInfo::getRegClass(llvm::Register) const (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMCodeGen.so.21.0git+0x31382c)
#10 0x00007fff926cb3e0 llvm::CoalescerPair::setRegisters(llvm::MachineInstr const*) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMCodeGen.so.21.0git+0x73b3e0)
#11 0x00007fff926d6d14 (anonymous namespace)::RegisterCoalescer::copyCoalesceWorkList(llvm::MutableArrayRef<llvm::MachineInstr*>) RegisterCoalescer.cpp:0:0
#12 0x00007fff926dd1f0 (anonymous namespace)::RegisterCoalescer::run(llvm::MachineFunction&) RegisterCoalescer.cpp:0:0
#13 0x00007fff926de290 (anonymous namespace)::RegisterCoalescerLegacy::runOnMachineFunction(llvm::MachineFunction&) RegisterCoalescer.cpp:0:0
#14 0x00007fff92424e80 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.100) MachineFunctionPass.cpp:0:0
#15 0x00007fff8e40fb5c llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMCore.so.21.0git+0x32fb5c)
#16 0x00007fff8e40feb8 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMCore.so.21.0git+0x32feb8)
#17 0x00007fff8e4110dc llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libLLVMCore.so.21.0git+0x3310dc)
#18 0x00007fff92eedfdc 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*) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangCodeGen.so.21.0git+0x14dfdc)
#19 0x00007fff9335fa1c clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangCodeGen.so.21.0git+0x5bfa1c)
#20 0x00007fff89f54204 clang::ParseAST(clang::Sema&, bool, bool) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/../lib/libclangParse.so.21.0git+0x44204)
#21 0x00007fff90ff920c clang::ASTFrontendAction::ExecuteAction() (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangFrontend.so.21.0git+0x17920c)
#22 0x00007fff93360700 clang::CodeGenAction::ExecuteAction() (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangCodeGen.so.21.0git+0x5c0700)
#23 0x00007fff910000c8 clang::FrontendAction::Execute() (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangFrontend.so.21.0git+0x1800c8)
#24 0x00007fff90f79340 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangFrontend.so.21.0git+0xf9340)
#25 0x00007fff952a6094 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/../lib/libclangFrontendTool.so.21.0git+0x6094)
#26 0x000000001001b2ac cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1.install/bin/clang+++0x1001b2ac)
#27 0x00000000100107e0 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#28 0x00007fff90b0c688 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

```

</details>

https://github.com/llvm/llvm-project/pull/131837