[clang] [llvm] [LLVM] Add IRNormalizer Pass (PR #68176)

[Yingwei Zheng via cfe-commits]

dtcxzyw wrote:

> > > I would also try to add this pass at the end of the clang pipeline and run llvm-test-suite to verify that the normalization this does is indeed semantics-preserving.
> > 
> > 
> > I'm running into some linking errors when trying to build [`llvm-test-suite`](https://github.com/llvm/llvm-test-suite/tree/main). Pinging for another round of review in the meantime.
> 
> I just tried this myself, and received the following failures. There were also a bunch of hanging processes I had to kill, but I didn't note down which those were.
> 
> ```
>   test-suite :: MicroBenchmarks/LCALS/SubsetALambdaLoops/lcalsALambda.test
>   test-suite :: MicroBenchmarks/LCALS/SubsetARawLoops/lcalsARaw.test
>   test-suite :: MicroBenchmarks/LCALS/SubsetBLambdaLoops/lcalsBLambda.test
>   test-suite :: MicroBenchmarks/LCALS/SubsetBRawLoops/lcalsBRaw.test
>   test-suite :: MicroBenchmarks/LCALS/SubsetCLambdaLoops/lcalsCLambda.test
>   test-suite :: MicroBenchmarks/LCALS/SubsetCRawLoops/lcalsCRaw.test
>   test-suite :: MultiSource/Applications/lua/lua.test
>   test-suite :: SingleSource/Benchmarks/CoyoteBench/huffbench.test
> ```
> 
> So I think there are still correctness issues in this pass.

I cannot reproduce these failures on my x86 machine.
```
Testing Time: 298.93s

Total Discovered Tests: 2438
  Passed: 2438 (100.00%)
```


https://github.com/llvm/llvm-project/pull/68176