[backend:X86][llvm:SelectionDAG][crash][regression] Self-hosting LLVM 21.1.x with -march=sapphirerapids hits combineSetCC APInt assertion (hiBit > BitWidth)

[DEVwXZ4Njdmo4hm]

Summary
When building LLVM 21.1.x with Clang 21.x and -march=sapphirerapids, the X86 backend deterministically crashes during SelectionDAG combine (combineSetCC) with an APInt assertion:

APInt::setBits/getLowBitsSet: hiBit <= BitWidth (hiBit out of range)

This happens even without LTO. Changing only -march to x86-64-v3 makes the crash disappear.

Environment

• OS: Linux x86_64 (triple: x86_64-pc-linux-gnu)
• Clang/LLD versions involved:
  • Works: host toolchain Clang 20.1.8 building LLVM 21.1.1
  • Fails: host toolchain Clang 21.1.0 or 21.1.1 building LLVM 21.1.1
• libc++: used for building (CLANG_DEFAULT_CXX_STDLIB=libc++; -stdlib=libc++)
• Assertions: ON (LLVM_ENABLE_ASSERTIONS=ON)
• LTO: not required to reproduce (OFF also crashes). FULL/Thin also reproduce when -march=sapphirerapids is used.
• CPU features: -march=sapphirerapids (enables AVX-512 family)

Affected versions

• Reproducible with Clang/LLVM 21.1.0 and 21.1.1 as host compilers.
• Not reproducible with Clang/LLVM 20.1.8 as host compiler (same source).

What I did (repro matrix)

1. Build LLVM 21.1.0 using Clang 20.1.8 → OK.
2. Build LLVM 21.1.1 using Clang 21.1.0 → Crash.
3. Build LLVM 21.1.1 using Clang 20.1.8 → OK.
4. Self-host: Build LLVM 21.1.1 using Clang 21.1.1 → same crash as in step 2.
5. Important: If I only change -march=sapphirerapids to -march=x86-64-v3 (keeping LTO as before), both the “20 builds 21” and “21 builds 21” builds succeed.

Minimal reproduction

• The crash happens while compiling this TU from LLVM itself:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
• Clang emits a preprocessed repro and a run script automatically. I will attach:
  • /tmp/InstructionCombining-XXXX.cpp
  • /tmp/InstructionCombining-XXXX.sh
• Running the script as-is (with -march=sapphirerapids) crashes; editing only -march to x86-64-v3 makes it pass.

Representative crash output:

[1612/11988] CCACHE_DIR=/dev/shm/CCACHE_dykecpWdGHYNcwwN CCACHE_MAXSIZE=50G CCACHE_CPP2=yes CCACHE_NOHASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /home/capri/.local/ccache/bin/ccache /home/capri/.local/llvm/selected/bin/clang++ -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/dev/shm/llvm-bdir/build/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/build/include -I/dev/shm/llvm-bdir/source/llvm/include -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -stdlib=libc++ -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 -UNDEBUG -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -c /dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
FAILED: lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o 
CCACHE_DIR=/dev/shm/CCACHE_dykecpWdGHYNcwwN CCACHE_MAXSIZE=50G CCACHE_CPP2=yes CCACHE_NOHASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /home/capri/.local/ccache/bin/ccache /home/capri/.local/llvm/selected/bin/clang++ -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/dev/shm/llvm-bdir/build/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/build/include -I/dev/shm/llvm-bdir/source/llvm/include -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -stdlib=libc++ -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 -UNDEBUG -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -c /dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
clang++: ../source/llvm/include/llvm/ADT/APInt.h:1368: void llvm::APInt::setBits(unsigned int, unsigned int): Assertion `hiBit <= BitWidth && "hiBit out of range"' 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/capri/.local/llvm/selected/bin/clang++ -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -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 -ffunction-sections -fdata-sections -O3 -std=c++17 -fPIC -fno-exceptions -funwind-tables -fdiagnostics-color -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Ilib/Transforms/InstCombine -I../source/llvm/lib/Transforms/InstCombine -Iinclude -I../source/llvm/include -stdlib=libc++ -DNDEBUG -UNDEBUG -c -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -fcolor-diagnostics -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o ../source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '../source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp'.
4.	Running pass 'X86 DAG->DAG Instruction Selection' on function '@_ZL16tryFactorizationRN4llvm14BinaryOperatorERKNS_13SimplifyQueryERNS_9IRBuilderINS_12TargetFolderENS_25IRBuilderCallbackInserterEEENS_11Instruction9BinaryOpsEPNS_5ValueESD_SD_SD_'
 #0 0x00007f9aba8908ea llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x2908ea)
 #1 0x00007f9aba88f307 llvm::sys::RunSignalHandlers() (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x28f307)
 #2 0x00007f9aba7780b1 CrashRecoverySignalHandler(int) ld-temp.o:0:0
 #3 0x00007f9aba467b40 __restore_rt (/lib64/libc.so.6+0x40b40)
 #4 0x00007f9aba4bd9dc __pthread_kill_implementation (/lib64/libc.so.6+0x969dc)
 #5 0x00007f9aba467a96 gsignal (/lib64/libc.so.6+0x40a96)
 #6 0x00007f9aba44f8fa abort (/lib64/libc.so.6+0x288fa)
 #7 0x00007f9aba44f81e _nl_load_domain.cold (/lib64/libc.so.6+0x2881e)
 #8 0x00007f9aba45fff6 (/lib64/libc.so.6+0x38ff6)
 #9 0x00007f9ac2fdbdfc llvm::APInt::getLowBitsSet(unsigned int, unsigned int) ld-temp.o:0:0
#10 0x00007f9ac31438bb combineSetCC(llvm::SDNode*, llvm::SelectionDAG&, llvm::TargetLowering::DAGCombinerInfo&, llvm::X86Subtarget const&) ld-temp.o:0:0
#11 0x00007f9ac310ac22 llvm::X86TargetLowering::PerformDAGCombine(llvm::SDNode*, llvm::TargetLowering::DAGCombinerInfo&) const (/home/capri/.local/llvm/selected/lib/libLLVMX86CodeGen.so.21.1+0x50ac22)
#12 0x00007f9ab9b34e13 (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) ld-temp.o:0:0
#13 0x00007f9ab9b346d5 llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::BatchAAResults*, llvm::CodeGenOptLevel) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x1346d5)
#14 0x00007f9ab9e58f60 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x458f60)
#15 0x00007f9ab9e55f9d llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x455f9d)
#16 0x00007f9ab9e51d20 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x451d20)
#17 0x00007f9ab9e4fe04 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x44fe04)
#18 0x00007f9abea51144 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/home/capri/.local/llvm/selected/lib/libLLVMCodeGen.so.21.1+0x651144)
#19 0x00007f9abaed4fa9 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d4fa9)
#20 0x00007f9abaee0fb4 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4e0fb4)
#21 0x00007f9abaed993b llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d993b)
#22 0x00007f9ac0efd9ea clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::__1::unique_ptr<llvm::raw_pwrite_stream, std::__1::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) (/home/capri/.local/llvm/selected/lib/libclangCodeGen.so.21.1+0x2fd9ea)
#23 0x00007f9ac131655e clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/home/capri/.local/llvm/selected/lib/libclangCodeGen.so.21.1+0x71655e)
#24 0x00007f9ab6ee58e9 clang::ParseAST(clang::Sema&, bool, bool) (/home/capri/.local/llvm/selected/lib/libclangParse.so.21.1+0x768e9)
#25 0x00007f9abd3d50b8 clang::FrontendAction::Execute() (/home/capri/.local/llvm/selected/lib/libclangFrontend.so.21.1+0x1d50b8)
#26 0x00007f9abd3336dd clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/capri/.local/llvm/selected/lib/libclangFrontend.so.21.1+0x1336dd)
#27 0x00007f9ac32f7a6f clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/capri/.local/llvm/selected/lib/libclangFrontendTool.so.21.1+0x7a6f)
#28 0x0000555c3a0989db cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/capri/.local/llvm/selected/bin/clang+++0x169db)
#29 0x0000555c3a09448f ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) ld-temp.o:0:0
#30 0x00007f9abcf3a1bf void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::__1::optional<llvm::StringRef>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*, bool*) const::$_0>(long) ld-temp.o:0:0
#31 0x00007f9aba77839c llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x17839c)
#32 0x00007f9abcf3a0a8 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::__1::optional<llvm::StringRef>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*, bool*) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0x13a0a8)
#33 0x00007f9abcef3bd1 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0xf3bd1)
#34 0x00007f9abcef3f8e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*>>&, bool) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0xf3f8e)
#35 0x00007f9abcf33f7e clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*>>&) (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0x133f7e)
#36 0x0000555c3a09389c clang_main(int, char**, llvm::ToolContext const&) (/home/capri/.local/llvm/selected/bin/clang+++0x1189c)
#37 0x0000555c3a0a322a main (/home/capri/.local/llvm/selected/bin/clang+++0x2122a)
#38 0x00007f9aba45130e __libc_start_call_main (/lib64/libc.so.6+0x2a30e)
#39 0x00007f9aba4513c9 __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x2a3c9)
#40 0x0000555c3a091925 _start (/home/capri/.local/llvm/selected/bin/clang+++0xf925)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
clang version 21.1.1
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /home/capri/.local/llvm/21/bin
Build config: +assertions
Configuration file: /home/capri/.config/clang/21/x86_64-pc-linux-gnu-clang++.cfg
clang++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/InstructionCombining-d6d78d.cpp
clang++: note: diagnostic msg: /tmp/InstructionCombining-d6d78d.sh
clang++: note: diagnostic msg: 

********************

Configuration knobs (for context)

• configure options (excerpt): LLVM_ENABLE_ASSERTIONS=ON, BUILD_SHARED_LIBS=ON, LLVM_ENABLE_LLD=ON, CLANG_DEFAULT_CXX_STDLIB=libc++, LLVM_UNREACHABLE_OPTIMIZE=ON, LLVM_ENABLE_LTO=OFF/FULL (either way reproduces with -march=sapphirerapids).
• common compile flags used when it crashes:
  -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain= -stdlib=libc++
• With the exact same setup but -march=x86-64-v3, the build succeeds.

Expected behavior
Compilation should succeed (no backend assertion) when building LLVM itself.

Actual behavior
Deterministic crash in X86 SelectionDAG combineSetCC due to APInt bitmask assertion when using -march=sapphirerapids.

Workarounds

• Build the toolchain itself with a baseline CPU (e.g. -march=x86-64-v3), or explicitly disable AVX-512 family features (e.g. -mno-avx512f -mno-avx512vl -mno-avx512bw -mno-avx512dq -mno-avx512cd -mno-avx512vbmi -mno-avx512vbmi2 -mno-avx512vnni ...).
• Disabling assertions “avoids” the abort but is not recommended.

Notes

• This looks distinct from regression in clang 20.1.8 / coroutines / distributed LTO: crash in optimizer #155558 (that one is about distributed ThinLTO post-link O0/coroutines passes). Here, LTO is not required and the crash happens while compiling a single TU from LLVM itself.
• The problem appears tied to the sapphirerapids/AVX-512 path in X86 DAG combine (combineSetCC computing an out-of-range APInt mask).

Attachments

• Please see the attached preprocessed source and run script produced by clang:
  • /tmp/InstructionCombining-d6d78d.cpp
  • /tmp/InstructionCombining-d6d78d.sh

InstructionCombining-d6d78d.cpp

InstructionCombining-d6d78d.sh

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: wXZ4Njdmo4hm (DEVwXZ4Njdmo4hm)

Summary When building LLVM 21.1.x with Clang 21.x and -march=sapphirerapids, the X86 backend deterministically crashes during SelectionDAG combine (combineSetCC) with an APInt assertion:

APInt::setBits/getLowBitsSet: hiBit <= BitWidth (hiBit out of range)

This happens even without LTO. Changing only -march to x86-64-v3 makes the crash disappear.

Environment

• OS: Linux x86_64 (triple: x86_64-pc-linux-gnu)
• Clang/LLD versions involved:
  • Works: host toolchain Clang 20.1.8 building LLVM 21.1.1
  • Fails: host toolchain Clang 21.1.0 or 21.1.1 building LLVM 21.1.1
• libc++: used for building (CLANG_DEFAULT_CXX_STDLIB=libc++; -stdlib=libc++)
• Assertions: ON (LLVM_ENABLE_ASSERTIONS=ON)
• LTO: not required to reproduce (OFF also crashes). FULL/Thin also reproduce when -march=sapphirerapids is used.
• CPU features: -march=sapphirerapids (enables AVX-512 family)

Affected versions

• Reproducible with Clang/LLVM 21.1.0 and 21.1.1 as host compilers.
• Not reproducible with Clang/LLVM 20.1.8 as host compiler (same source).

What I did (repro matrix)

1. Build LLVM 21.1.0 using Clang 20.1.8 → OK.
2. Build LLVM 21.1.1 using Clang 21.1.0 → Crash.
3. Build LLVM 21.1.1 using Clang 20.1.8 → OK.
4. Self-host: Build LLVM 21.1.1 using Clang 21.1.1 → same crash as in step 2.
5. Important: If I only change -march=sapphirerapids to -march=x86-64-v3 (keeping LTO as before), both the “20 builds 21” and “21 builds 21” builds succeed.

Minimal reproduction

• The crash happens while compiling this TU from LLVM itself:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
• Clang emits a preprocessed repro and a run script automatically. I will attach:
  • /tmp/InstructionCombining-XXXX.cpp
  • /tmp/InstructionCombining-XXXX.sh
• Running the script as-is (with -march=sapphirerapids) crashes; editing only -march to x86-64-v3 makes it pass.

Representative crash output:

[1612/11988] CCACHE_DIR=/dev/shm/CCACHE_dykecpWdGHYNcwwN CCACHE_MAXSIZE=50G CCACHE_CPP2=yes CCACHE_NOHASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /home/capri/.local/ccache/bin/ccache /home/capri/.local/llvm/selected/bin/clang++ -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/dev/shm/llvm-bdir/build/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/build/include -I/dev/shm/llvm-bdir/source/llvm/include -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -stdlib=libc++ -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 -UNDEBUG -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -c /dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
FAILED: lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o 
CCACHE_DIR=/dev/shm/CCACHE_dykecpWdGHYNcwwN CCACHE_MAXSIZE=50G CCACHE_CPP2=yes CCACHE_NOHASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /home/capri/.local/ccache/bin/ccache /home/capri/.local/llvm/selected/bin/clang++ -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/dev/shm/llvm-bdir/build/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine -I/dev/shm/llvm-bdir/build/include -I/dev/shm/llvm-bdir/source/llvm/include -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -stdlib=libc++ -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 -UNDEBUG -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -c /dev/shm/llvm-bdir/source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
clang++: ../source/llvm/include/llvm/ADT/APInt.h:1368: void llvm::APInt::setBits(unsigned int, unsigned int): Assertion `hiBit <= BitWidth && "hiBit out of range"' 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/capri/.local/llvm/selected/bin/clang++ -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=/home/capri/.local/gcc/selected -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 -ffunction-sections -fdata-sections -O3 -std=c++17 -fPIC -fno-exceptions -funwind-tables -fdiagnostics-color -DEXPERIMENTAL_KEY_INSTRUCTIONS -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Ilib/Transforms/InstCombine -I../source/llvm/lib/Transforms/InstCombine -Iinclude -I../source/llvm/include -stdlib=libc++ -DNDEBUG -UNDEBUG -c -MD -MT lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o -MF lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o.d -fcolor-diagnostics -o lib/Transforms/InstCombine/CMakeFiles/LLVMInstCombine.dir/InstructionCombining.cpp.o ../source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '../source/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp'.
4.	Running pass 'X86 DAG-&gt;DAG Instruction Selection' on function '@<!-- -->_ZL16tryFactorizationRN4llvm14BinaryOperatorERKNS_13SimplifyQueryERNS_9IRBuilderINS_12TargetFolderENS_25IRBuilderCallbackInserterEEENS_11Instruction9BinaryOpsEPNS_5ValueESD_SD_SD_'
 #<!-- -->0 0x00007f9aba8908ea llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x2908ea)
 #<!-- -->1 0x00007f9aba88f307 llvm::sys::RunSignalHandlers() (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x28f307)
 #<!-- -->2 0x00007f9aba7780b1 CrashRecoverySignalHandler(int) ld-temp.o:0:0
 #<!-- -->3 0x00007f9aba467b40 __restore_rt (/lib64/libc.so.6+0x40b40)
 #<!-- -->4 0x00007f9aba4bd9dc __pthread_kill_implementation (/lib64/libc.so.6+0x969dc)
 #<!-- -->5 0x00007f9aba467a96 gsignal (/lib64/libc.so.6+0x40a96)
 #<!-- -->6 0x00007f9aba44f8fa abort (/lib64/libc.so.6+0x288fa)
 #<!-- -->7 0x00007f9aba44f81e _nl_load_domain.cold (/lib64/libc.so.6+0x2881e)
 #<!-- -->8 0x00007f9aba45fff6 (/lib64/libc.so.6+0x38ff6)
 #<!-- -->9 0x00007f9ac2fdbdfc llvm::APInt::getLowBitsSet(unsigned int, unsigned int) ld-temp.o:0:0
#<!-- -->10 0x00007f9ac31438bb combineSetCC(llvm::SDNode*, llvm::SelectionDAG&amp;, llvm::TargetLowering::DAGCombinerInfo&amp;, llvm::X86Subtarget const&amp;) ld-temp.o:0:0
#<!-- -->11 0x00007f9ac310ac22 llvm::X86TargetLowering::PerformDAGCombine(llvm::SDNode*, llvm::TargetLowering::DAGCombinerInfo&amp;) const (/home/capri/.local/llvm/selected/lib/libLLVMX86CodeGen.so.21.1+0x50ac22)
#<!-- -->12 0x00007f9ab9b34e13 (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) ld-temp.o:0:0
#<!-- -->13 0x00007f9ab9b346d5 llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::BatchAAResults*, llvm::CodeGenOptLevel) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x1346d5)
#<!-- -->14 0x00007f9ab9e58f60 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x458f60)
#<!-- -->15 0x00007f9ab9e55f9d llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x455f9d)
#<!-- -->16 0x00007f9ab9e51d20 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x451d20)
#<!-- -->17 0x00007f9ab9e4fe04 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x44fe04)
#<!-- -->18 0x00007f9abea51144 llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMCodeGen.so.21.1+0x651144)
#<!-- -->19 0x00007f9abaed4fa9 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d4fa9)
#<!-- -->20 0x00007f9abaee0fb4 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4e0fb4)
#<!-- -->21 0x00007f9abaed993b llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d993b)
#<!-- -->22 0x00007f9ac0efd9ea clang::emitBackendOutput(clang::CompilerInstance&amp;, clang::CodeGenOptions&amp;, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::__1::unique_ptr&lt;llvm::raw_pwrite_stream, std::__1::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;, clang::BackendConsumer*) (/home/capri/.local/llvm/selected/lib/libclangCodeGen.so.21.1+0x2fd9ea)
#<!-- -->23 0x00007f9ac131655e clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&amp;) (/home/capri/.local/llvm/selected/lib/libclangCodeGen.so.21.1+0x71655e)
#<!-- -->24 0x00007f9ab6ee58e9 clang::ParseAST(clang::Sema&amp;, bool, bool) (/home/capri/.local/llvm/selected/lib/libclangParse.so.21.1+0x768e9)
#<!-- -->25 0x00007f9abd3d50b8 clang::FrontendAction::Execute() (/home/capri/.local/llvm/selected/lib/libclangFrontend.so.21.1+0x1d50b8)
#<!-- -->26 0x00007f9abd3336dd clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/home/capri/.local/llvm/selected/lib/libclangFrontend.so.21.1+0x1336dd)
#<!-- -->27 0x00007f9ac32f7a6f clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/capri/.local/llvm/selected/lib/libclangFrontendTool.so.21.1+0x7a6f)
#<!-- -->28 0x0000555c3a0989db cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/home/capri/.local/llvm/selected/bin/clang+++0x169db)
#<!-- -->29 0x0000555c3a09448f ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) ld-temp.o:0:0
#<!-- -->30 0x00007f9abcf3a1bf void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::__1::optional&lt;llvm::StringRef&gt;&gt;, std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;, std::__1::allocator&lt;char&gt;&gt;*, bool*) const::$_0&gt;(long) ld-temp.o:0:0
#<!-- -->31 0x00007f9aba77839c llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x17839c)
#<!-- -->32 0x00007f9abcf3a0a8 clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::__1::optional&lt;llvm::StringRef&gt;&gt;, std::__1::basic_string&lt;char, std::__1::char_traits&lt;char&gt;, std::__1::allocator&lt;char&gt;&gt;*, bool*) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0x13a0a8)
#<!-- -->33 0x00007f9abcef3bd1 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0xf3bd1)
#<!-- -->34 0x00007f9abcef3f8e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::__1::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0xf3f8e)
#<!-- -->35 0x00007f9abcf33f7e clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::__1::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/home/capri/.local/llvm/selected/lib/libclangDriver.so.21.1+0x133f7e)
#<!-- -->36 0x0000555c3a09389c clang_main(int, char**, llvm::ToolContext const&amp;) (/home/capri/.local/llvm/selected/bin/clang+++0x1189c)
#<!-- -->37 0x0000555c3a0a322a main (/home/capri/.local/llvm/selected/bin/clang+++0x2122a)
#<!-- -->38 0x00007f9aba45130e __libc_start_call_main (/lib64/libc.so.6+0x2a30e)
#<!-- -->39 0x00007f9aba4513c9 __libc_start_main@<!-- -->GLIBC_2.2.5 (/lib64/libc.so.6+0x2a3c9)
#<!-- -->40 0x0000555c3a091925 _start (/home/capri/.local/llvm/selected/bin/clang+++0xf925)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
clang version 21.1.1
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /home/capri/.local/llvm/21/bin
Build config: +assertions
Configuration file: /home/capri/.config/clang/21/x86_64-pc-linux-gnu-clang++.cfg
clang++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/InstructionCombining-d6d78d.cpp
clang++: note: diagnostic msg: /tmp/InstructionCombining-d6d78d.sh
clang++: note: diagnostic msg: 

********************

Configuration knobs (for context)

• configure options (excerpt): LLVM_ENABLE_ASSERTIONS=ON, BUILD_SHARED_LIBS=ON, LLVM_ENABLE_LLD=ON, CLANG_DEFAULT_CXX_STDLIB=libc++, LLVM_UNREACHABLE_OPTIMIZE=ON, LLVM_ENABLE_LTO=OFF/FULL (either way reproduces with -march=sapphirerapids).
• common compile flags used when it crashes:
  -march=sapphirerapids -O3 -pipe -fstack-protector-all -fcf-protection=full -fstack-clash-protection -fstrict-flex-arrays=3 --gcc-toolchain=<path> -stdlib=libc++
• With the exact same setup but -march=x86-64-v3, the build succeeds.

Expected behavior
Compilation should succeed (no backend assertion) when building LLVM itself.

Actual behavior
Deterministic crash in X86 SelectionDAG combineSetCC due to APInt bitmask assertion when using -march=sapphirerapids.

Workarounds

• Build the toolchain itself with a baseline CPU (e.g. -march=x86-64-v3), or explicitly disable AVX-512 family features (e.g. -mno-avx512f -mno-avx512vl -mno-avx512bw -mno-avx512dq -mno-avx512cd -mno-avx512vbmi -mno-avx512vbmi2 -mno-avx512vnni ...).
• Disabling assertions “avoids” the abort but is not recommended.

Notes

• This looks distinct from #155558 (that one is about distributed ThinLTO post-link O0/coroutines passes). Here, LTO is not required and the crash happens while compiling a single TU from LLVM itself.
• The problem appears tied to the sapphirerapids/AVX-512 path in X86 DAG combine (combineSetCC computing an out-of-range APInt mask).

Attachments

• Please see the attached preprocessed source and run script produced by clang:
  • /tmp/InstructionCombining-d6d78d.cpp
  • /tmp/InstructionCombining-d6d78d.sh

InstructionCombining-d6d78d.cpp

InstructionCombining-d6d78d.sh

[phoebewang]

I cannot reproduce the crash on both main trunk and release/21.x branch using the attached files.

[DEVwXZ4Njdmo4hm]

Update: IR- and llc-level reproducer attached (not reduced)

I’ve attached an IR file generated from the existing preprocessed reproducer. This is not further reduced, but llc reproduces the same backend assertion with -mcpu=sapphirerapids.

Attachments：InstructionCombining-d6d78d-ll.tar.gz
SHA256：2f025ba4acca5b97efc84abdba91387e0bd3bdb0b1001ce86fd2d7502be6009b

~ llc -mtriple=x86_64-pc-linux-gnu -mcpu=sapphirerapids -O3 InstructionCombining-d6d78d.ll -filetype=null
llc: ../source/llvm/include/llvm/ADT/APInt.h:1368: void llvm::APInt::setBits(unsigned int, unsigned int): Assertion `hiBit <= BitWidth && "hiBit out of range"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: llc -mtriple=x86_64-pc-linux-gnu -mcpu=sapphirerapids -O3 InstructionCombining-d6d78d.ll -filetype=null
1.	Running pass 'Function Pass Manager' on module 'InstructionCombining-d6d78d.ll'.
2.	Running pass 'X86 DAG->DAG Instruction Selection' on function '@_ZL16tryFactorizationRN4llvm14BinaryOperatorERKNS_13SimplifyQueryERNS_9IRBuilderINS_12TargetFolderENS_25IRBuilderCallbackInserterEEENS_11Instruction9BinaryOpsEPNS_5ValueESD_SD_SD_'
 #0 0x00007fac6a08e78a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x28e78a)
 #1 0x00007fac6a08d197 llvm::sys::RunSignalHandlers() (/home/capri/.local/llvm/selected/lib/libLLVMSupport.so.21.1+0x28d197)
 #2 0x00007fac6a08ded4 SignalHandler(int, siginfo_t*, void*) ld-temp.o:0:0
 #3 0x00007fac69c67b40 __restore_rt (/lib64/libc.so.6+0x40b40)
 #4 0x00007fac69cbd9dc __pthread_kill_implementation (/lib64/libc.so.6+0x969dc)
 #5 0x00007fac69c67a96 gsignal (/lib64/libc.so.6+0x40a96)
 #6 0x00007fac69c4f8fa abort (/lib64/libc.so.6+0x288fa)
 #7 0x00007fac69c4f81e _nl_load_domain.cold (/lib64/libc.so.6+0x2881e)
 #8 0x00007fac69c5fff6 (/lib64/libc.so.6+0x38ff6)
 #9 0x00007fac6f3d731c llvm::APInt::getLowBitsSet(unsigned int, unsigned int) ld-temp.o:0:0
#10 0x00007fac6f53e586 combineSetCC(llvm::SDNode*, llvm::SelectionDAG&, llvm::TargetLowering::DAGCombinerInfo&, llvm::X86Subtarget const&) ld-temp.o:0:0
#11 0x00007fac6f505028 llvm::X86TargetLowering::PerformDAGCombine(llvm::SDNode*, llvm::TargetLowering::DAGCombinerInfo&) const (/home/capri/.local/llvm/selected/lib/libLLVMX86CodeGen.so.21.1+0x505028)
#12 0x00007fac6c934453 (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) ld-temp.o:0:0
#13 0x00007fac6c933d36 llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::BatchAAResults*, llvm::CodeGenOptLevel) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x133d36)
#14 0x00007fac6cc4f050 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x44f050)
#15 0x00007fac6cc4c188 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x44c188)
#16 0x00007fac6cc47db0 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x447db0)
#17 0x00007fac6cc45e94 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/home/capri/.local/llvm/selected/lib/libLLVMSelectionDAG.so.21.1+0x445e94)
#18 0x00007fac6c244074 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/home/capri/.local/llvm/selected/lib/libLLVMCodeGen.so.21.1+0x644074)
#19 0x00007fac6a6d2e29 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d2e29)
#20 0x00007fac6a6de664 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4de664)
#21 0x00007fac6a6d744b llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/capri/.local/llvm/selected/lib/libLLVMCore.so.21.1+0x4d744b)
#22 0x0000563bc287f824 main (/home/capri/.local/llvm/21/bin/llc+0x26824)
#23 0x00007fac69c5130e __libc_start_call_main (/lib64/libc.so.6+0x2a30e)
#24 0x00007fac69c513c9 __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x2a3c9)
#25 0x0000563bc2875515 _start (/home/capri/.local/llvm/21/bin/llc+0x1c515)
[1]    80553 IOT instruction (core dumped)  llc -mtriple=x86_64-pc-linux-gnu -mcpu=sapphirerapids -O3  -filetype=null

InstructionCombining-d6d78d-ll.tar.gz

[phoebewang]

The attatched IR cannot be reproduced either.

[abhishek-kaushik22]

This looks similar to #155762 and was fixed in 33b2c26. Maybe we should backport the commit to 21.1

[phoebewang]

Oh, it turns out I didn't enable LLVM_ENABLE_ASSERTIONS=ON when build release/21.x

[DEVwXZ4Njdmo4hm]

The attatched IR cannot be reproduced either.

Thanks for checking. A few details that seem required to reproduce on my side:

• The failing llc is built with assertions ON.
• llc was built with Clang 21.1.x as the host compiler. If I build llc with Clang 20.x or GCC, I cannot reproduce.
• The IR embeds target-cpu=sapphirerapids and AVX-512 features; the command-line matches.

On my machine:

llc -mtriple=x86_64-pc-linux-gnu -mcpu=sapphirerapids -O3 InstructionCombining-d6d78d.ll -filetype=null
# -> asserts in APInt::setBits (combineSetCC)

llc -mtriple=x86_64-pc-linux-gnu -mcpu=x86-64-v3 -O3 InstructionCombining-d6d78d.ll -filetype=null
# -> completes

Could you confirm whether your llc has assertions enabled and share your llc --version?
Here is mine for the failing binary:

~ llc --version                                                                                          
LLVM (http://llvm.org/):
  LLVM version 21.1.1
  Optimized build with assertions.
  Default target: x86_64-pc-linux-gnu
  Host CPU: sapphirerapids

  Registered Targets:
    aarch64     - AArch64 (little endian)
    aarch64_32  - AArch64 (little endian ILP32)
    aarch64_be  - AArch64 (big endian)
    amdgcn      - AMD GCN GPUs
    arm         - ARM
    arm64       - ARM64 (little endian)
    arm64_32    - ARM64 (little endian ILP32)
    armeb       - ARM (big endian)
    avr         - Atmel AVR Microcontroller
    bpf         - BPF (host endian)
    bpfeb       - BPF (big endian)
    bpfel       - BPF (little endian)
    hexagon     - Hexagon
    lanai       - Lanai
    loongarch32 - 32-bit LoongArch
    loongarch64 - 64-bit LoongArch
    mips        - MIPS (32-bit big endian)
    mips64      - MIPS (64-bit big endian)
    mips64el    - MIPS (64-bit little endian)
    mipsel      - MIPS (32-bit little endian)
    msp430      - MSP430 [experimental]
    nvptx       - NVIDIA PTX 32-bit
    nvptx64     - NVIDIA PTX 64-bit
    ppc32       - PowerPC 32
    ppc32le     - PowerPC 32 LE
    ppc64       - PowerPC 64
    ppc64le     - PowerPC 64 LE
    r600        - AMD GPUs HD2XXX-HD6XXX
    riscv32     - 32-bit RISC-V
    riscv64     - 64-bit RISC-V
    sparc       - Sparc
    sparcel     - Sparc LE
    sparcv9     - Sparc V9
    spirv       - SPIR-V Logical
    spirv32     - SPIR-V 32-bit
    spirv64     - SPIR-V 64-bit
    systemz     - SystemZ
    thumb       - Thumb
    thumbeb     - Thumb (big endian)
    ve          - VE
    wasm32      - WebAssembly 32-bit
    wasm64      - WebAssembly 64-bit
    x86         - 32-bit X86: Pentium-Pro and above
    x86-64      - 64-bit X86: EM64T and AMD64
    xcore       - XCore