[llvm] ConstraintElim: add dry-run routine to fail early (PR #99670)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> New results look good: http://llvm-compile-time-tracker.com/compare.php?from=c5ee3c05ca61f3fae11337c5853aee7b450a9dc6&to=50c2e95b9a66395d5f6b62a99e67fec1a874f8f5&stat=instructions%3Au.
> 
> @dtcxzyw Could you kindly check the latest commit against your data set?

```
Top 5 improvements:
  darktable/FujiDecompressor.cpp.ll 3874209532 3001864479 -22.52%
  openjdk/ad_x86_gen.ll 20827921447 18376594487 -11.77%
  cmake/cmPolicies.cxx.ll 2196055101 2081555278 -5.21%
  php/metaphone.ll 3643053889 3457411868 -5.10%
  faiss/IndexIVFAdditiveQuantizerFastScan.cpp.ll 874177979 835608401 -4.41%
Top 5 regressions:
  lightgbm/linear_tree_learner.cpp.ll 9935337605 10245318195 +3.12%
  lightgbm/sample_strategy.cpp.ll 1000916300 1027777356 +2.68%
  gromacs/propagator.cpp.ll 7940003968 8151320784 +2.66%
  meshlab/arap.cpp.ll 16215819406 16630930530 +2.56%
  gromacs/statepropagatordata.cpp.ll 3171332547 3251119016 +2.52%
Overall: 0.06266579%
```

https://github.com/llvm/llvm-project/pull/99670