[llvm] [Analysis] Enchance alignment propagation in computeKnownBits. (PR #171828)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> So is compilation time normal? [dtcxzyw/llvm-opt-benchmark#3148 (comment)](https://github.com/dtcxzyw/llvm-opt-benchmark/pull/3148#issuecomment-3642849763)

No. I'd expect the slowdown to be less than +0.05%.
You can use the following commands to reproduce locally:
```
wget https://raw.githubusercontent.com/dtcxzyw/llvm-opt-benchmark/refs/heads/main/bench/glslang/original/glslang_tab.ll
perf -e instructions:u <old_llvm>/bin/opt -O3 glslang_tab.ll --disable-output
perf -e instructions:u <new_llvm>bin/opt -O3 glslang_tab.ll --disable-output
```


https://github.com/llvm/llvm-project/pull/171828