[llvm] [InstCombine] Extend folding of aggregate construction to cases when source aggregates are partially available (PR #100828)

[via llvm-commits]

weiguozhi wrote:

@dtcxzyw could you help to explain these numbers? Execution time? File size? Number of llvm IR instructions?
 
```
Top 5 improvements:
  minetest/s_client.cpp.ll 300581269 294367598 -2.07%
  abseil-cpp/kernel_timeout_test.cc.ll 1973629781 1937840415 -1.81%
  cmake/cmFindBase.cxx.ll 1913629020 1891008778 -1.18%
  assimp/IFCReaderGen2_2x3.cpp.ll 3046110312 3017099134 -0.95%
  darktable/lut3dgmic.cpp.ll 236183674 234289794 -0.80%
Top 5 regressions:
  minetest/test_connection.cpp.ll 682795465 698591227 +2.31%
  cmake/cmQtAutoMocUic.cxx.ll 8264379610 8383878253 +1.45%
  tokio-rs/132n8ebvfaa2dg8b.ll 82150296 82583502 +0.53%
  tokio-rs/40sgumesnmyyffj3.ll 67652318 67979824 +0.48%
  spike/f128_rem.ll 123368228 123914940 +0.44%

Overall: 0.01762297%
```

I can guess out the numbers in other two parts, the llvm stats result and the changed lines in diff result.


https://github.com/llvm/llvm-project/pull/100828