[llvm] Calculate KnownBits from Metadata correctly for vector loads (PR #128908)

[Augie Fackler via llvm-commits]

durin42 wrote:

That yielded
```
t24: v16i8,ch = load<(load (s128) from %ir.<badref>, !alias.scope <0x7fd6d812dc28>, !noalias <0x7fd6d812dc58>, !range <0x7fd6d80869d0>)> t0, t7, undef:i64
<0x7fd6d80869d0> = !{i128 0, i128 3}
rustc: /usr/local/google/home/augie/Programming/big/rust/src/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:4016: llvm::KnownBits llvm::SelectionDAG::computeKnownBits(llvm::SDValue, const llvm::APInt&, unsigned int) const: Assertion `0' failed.
```

Hopefully that helps - I've also got things sorted so I can get the invocation open in `lldb` if that would help for me to inspect some stuff here.

https://github.com/llvm/llvm-project/pull/128908