[llvm] [VectorCombine] Combine adjacent loads feeding as shuffle operands (PR #213007)

Tue Aug 11 01:21:05 PDT 2026

dtcxzyw wrote:

The following correctness issue was found by [llvm-hackme](https://github.com/dtcxzyw/llvm-hackme).

<!-- llvm-hackme-state: bug_found -->
<!-- llvm-hackme-baseline: febf50748effc5fb381ad479cf129f1ebcdc4bec -->
<!-- llvm-hackme-head-sha: 3c0f83bba16caf84e842bf26db1a1ce916340ac2 -->
<!-- llvm-hackme-patch-sha256: 4377b1ec6b9025e73f4124c640a372a63210dfcc60d4f85be2cba564bbb4cd37 -->
<!-- llvm-hackme-kind: crash -->

This comment is generated by an automated correctness checking service designed to help identify critical correctness bugs (opt crashes or Alive2 miscompilations) and improve PR review efficiency under limited reviewer bandwidth.

The reproducer was generated by LLM.

This bug is a regression introduced by this PR. It does not reproduce on the baseline commit.

## Reproducer

**Kind**: crash

**IR Reproducer**:
```llvm
; RUN: opt -passes=vector-combine -S
define <2 x i8> @t(ptr %p) {
  %p16 = getelementptr inbounds i8, ptr %p, i64 1073741823
  %a = load <1073741823 x i8>, ptr %p
  %b = load <1073741823 x i8>, ptr %p16
  %s = shufflevector <1073741823 x i8> %a, <1073741823 x i8> %b, <2 x i32> <i32 0, i32 1>
  ret <2 x i8> %s
}
```

**Stacktrace**:
```
opt: ../llvm-project-pr/llvm/lib/IR/Instructions.cpp:1802: llvm::ShuffleVectorInst::ShuffleVectorInst(llvm::Value*, llvm::Value*, llvm::ArrayRef<int>, const llvm::Twine&, llvm::InsertPosition): Assertion `isValidOperands(V1, V2, Mask) && "Invalid shuffle vector instruction operands!"' 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: /llvm-hackme/work/llvm-hackme/llvm-build-pr/bin/opt -S -o /dev/null /tmp/tmprd0q3xgh.ll -passes=vector-combine
1.	Running pass "function(vector-combine)" on module "/tmp/tmprd0q3xgh.ll"
2.	Running pass "vector-combine" on function "t"
 #0 0x00007ffff7e1a092 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Support/Unix/Signals.inc:931:22
 #1 0x00007ffff7e16ccc llvm::sys::RunSignalHandlers() /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Support/Signals.cpp:108:20
 #2 0x00007ffff7e16ed5 SignalHandler(int, siginfo_t*, void*) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Support/Unix/Signals.inc:474:14
 #3 0x00007ffff7a19520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007ffff7a6d9fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007ffff7a19476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007ffff79ff7f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007ffff79ff71b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007ffff7a10e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00007fffedc7a399 llvm::ShuffleVectorInst::ShuffleVectorInst(llvm::Value*, llvm::Value*, llvm::ArrayRef<int>, llvm::Twine const&, llvm::InsertPosition) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/IR/Instructions.cpp:1802:3
#10 0x00007ffff07a10a9 llvm::ShuffleVectorInst* llvm::IRBuilderBase::Insert<llvm::ShuffleVectorInst>(llvm::ShuffleVectorInst*, llvm::Twine const&) const /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/IRBuilder.h:147:5
#11 0x00007ffff07a10a9 llvm::IRBuilderBase::CreateShuffleVector(llvm::Value*, llvm::Value*, llvm::ArrayRef<int>, llvm::Twine const&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/IRBuilder.h:2696:18
#12 0x00007ffff09316f1 (anonymous namespace)::VectorCombine::foldShuffleOfAdjacentLoads(llvm::Instruction&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Transforms/Vectorize/VectorCombine.cpp:6603:49
#13 0x00007ffff0932b77 (anonymous namespace)::VectorCombine::run()::'lambda'(llvm::Instruction&)::operator()(llvm::Instruction&) const /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Transforms/Vectorize/VectorCombine.cpp:6805:9
#14 0x00007ffff0934869 run /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Transforms/Vectorize/VectorCombine.cpp:6907:9
#15 0x00007ffff0934869 llvm::VectorCombinePass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/Transforms/Vectorize/VectorCombine.cpp:6941:20
#16 0x00007ffff145e806 llvm::detail::PassModel<llvm::Function, llvm::VectorCombinePass, llvm::AnalysisManager<llvm::Function> >::runImpl(llvm::detail::PassConcept<llvm::Function, llvm::AnalysisManager<llvm::Function> >&, llvm::Function&, llvm::AnalysisManager<llvm::Function>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/PassManagerInternal.h:129:3
#17 0x00007fffedd03768 llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function> >::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/PassManagerImpl.h:80:18
#18 0x00007ffff145c5a6 llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function> >, llvm::AnalysisManager<llvm::Function> >::runImpl(llvm::detail::PassConcept<llvm::Function, llvm::AnalysisManager<llvm::Function> >&, llvm::Function&, llvm::AnalysisManager<llvm::Function>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/PassManagerInternal.h:129:3
#19 0x00007fffedd0255c llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/lib/IR/PassManager.cpp:132:41
#20 0x00007ffff145ff36 llvm::detail::PassModel<llvm::Module, llvm::ModuleToFunctionPassAdaptor, llvm::AnalysisManager<llvm::Module> >::runImpl(llvm::detail::PassConcept<llvm::Module, llvm::AnalysisManager<llvm::Module> >&, llvm::Module&, llvm::AnalysisManager<llvm::Module>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/PassManagerInternal.h:129:3
#21 0x00007fffedd01fb8 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module> >::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/PassManagerImpl.h:80:18
#22 0x00007ffff7f94874 llvm::SmallPtrSetImplBase::~SmallPtrSetImplBase() /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/ADT/SmallPtrSet.h:89:5
#23 0x00007ffff7f94874 llvm::SmallPtrSetImpl<llvm::AnalysisKey*>::~SmallPtrSetImpl() /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/ADT/SmallPtrSet.h:365:35
#24 0x00007ffff7f94874 llvm::SmallPtrSet<llvm::AnalysisKey*, 2u>::~SmallPtrSet() /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/ADT/SmallPtrSet.h:532:7
#25 0x00007ffff7f94874 llvm::PreservedAnalyses::~PreservedAnalyses() /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/include/llvm/IR/Analysis.h:112:7
#26 0x00007ffff7f94874 llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::PassPlugin>, llvm::ArrayRef<std::function<void (llvm::PassBuilder&)> >, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool, bool) /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/tools/opt/NewPMDriver.cpp:580:10
#27 0x00007ffff7fa18c4 optMain /llvm-hackme/work/llvm-hackme/llvm-build-pr/../llvm-project-pr/llvm/tools/opt/optdriver.cpp:805:25
#28 0x00007ffff7a00d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#29 0x00007ffff7a00e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#30 0x0000555555555095 _start (/llvm-hackme/work/llvm-hackme/llvm-build-pr/bin/opt+0x1095)
```

**Baseline Revision**: `febf50748effc5fb381ad479cf129f1ebcdc4bec`
**PR Head SHA**: `3c0f83bba16caf84e842bf26db1a1ce916340ac2`
**Patch SHA256**: `4377b1ec6b9025e73f4124c640a372a63210dfcc60d4f85be2cba564bbb4cd37`

https://github.com/llvm/llvm-project/pull/213007