[llvm] [SLP] NFC. Use InstructionsState::valid if users just want to know whether VL has same opcode. (PR #120217)

[Han-Kuan Chen via llvm-commits]

HanKuanChen wrote:

> I'm seeing this when doing check-llvm:
> 
> ```
> clang++: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:821: llvm::Instruction* {anonymous}::InstructionsState::getMainOp() const: Assertion `valid() && "InstructionsState is invalid."' failed.
> ```
> 
> This happens when compiling `llvm/unittests/ADT/DenseMapTest.cpp`, did anyone else observe that too?

This may be solved by https://github.com/llvm/llvm-project/pull/122443.
BTW, can you provide the command you use?

https://github.com/llvm/llvm-project/pull/120217