[Polly] clang crashes in ZoneAlgorithm::computeKnownFromLoad with -O3 -mllvm -polly

This case was generated by fuzzer and was reduced.

Reproducer: https://godbolt.org/z/Y8v1fza38
- Attachments
- [crash.c](https://github.com/user-attachments/files/30043532/crash.c)
- [crash-bd7b93.sh](https://github.com/user-attachments/files/30043533/crash-bd7b93.sh)
- [crash-bd7b93.c](https://github.com/user-attachments/files/30043534/crash-bd7b93.c)

Compiler version: `clang version 23.0.0git (https://github.com/llvm/llvm-project.git 12ce00a865b09cb72a3ea9a84f9308236a4f6038) + assertions`

Compile command: `clang -O3 -mllvm -polly crash.c`

Backtrace: [bt.txt](https://github.com/user-attachments/files/30043639/bt.txt)

Start by compiling the attached crash.c or crash-bd7b93.c with clang -O3 -mllvm -polly, using the Godbolt reproducer to confirm the failure. Read bt.txt and trace the crash into Polly's ZoneAlgorithm::computeKnownFromLoad; done means the reproducer no longer makes clang crash.

Written by the indexing model from the issue text.