[llvm] [LoopUnroll] Consider simplified operands while retrieving TTI instruction cost (PR #70929)

[Sergey Kachkov via llvm-commits]

skachkov-sc wrote:

Ping
<details>
<summary>Number of completely unrolled loops after this change on test-suite (-Os build)</summary>

```
Program                                                                       loop-unroll.NumCompletelyUnrolled              
                                                                              before                            after  diff  
     test-suite :: MicroBenchmarks/LCALS/SubsetCLambdaLoops/lcalsCLambda.test   0.00                             27.00   inf%
           test-suite :: MicroBenchmarks/LCALS/SubsetARawLoops/lcalsARaw.test   0.00                             27.00   inf%
      test-suite :: MultiSource/Benchmarks/mediabench/jpeg/jpeg-6a/cjpeg.test   0.00                              2.00   inf%
    test-suite :: MultiSource/Benchmarks/DOE-ProxyApps-C/miniGMG/miniGMG.test   0.00                              2.00   inf%
                      test-suite :: MultiSource/Benchmarks/nbench/nbench.test   0.00                              1.00   inf%
               test-suite :: MultiSource/Benchmarks/mafft/pairlocalalign.test   0.00                              1.00   inf%
           test-suite :: MicroBenchmarks/LCALS/SubsetCRawLoops/lcalsCRaw.test   0.00                             27.00   inf%
           test-suite :: MicroBenchmarks/LCALS/SubsetBRawLoops/lcalsBRaw.test   0.00                             27.00   inf%
     test-suite :: MicroBenchmarks/LCALS/SubsetBLambdaLoops/lcalsBLambda.test   0.00                             27.00   inf%
test-suite :: MultiSource/Benchmarks/MiBench/consumer-jpeg/consumer-jpeg.test   0.00                              2.00   inf%
     test-suite :: MicroBenchmarks/LCALS/SubsetALambdaLoops/lcalsALambda.test   0.00                             27.00   inf%
                        test-suite :: MultiSource/Benchmarks/Olden/bh/bh.test   0.00                              3.00   inf%
                test-suite :: External/SPEC/CINT2006/456.hmmer/456.hmmer.test   0.00                              2.00   inf%
               test-suite :: External/SPEC/CFP2006/453.povray/453.povray.test   0.00                              2.00   inf%
                      test-suite :: MultiSource/Benchmarks/Bullet/bullet.test   1.00                              6.00 500.0%
                 test-suite :: MultiSource/Applications/JM/ldecod/ldecod.test   1.00                              5.00 400.0%
                 test-suite :: MultiSource/Applications/JM/lencod/lencod.test   2.00                             10.00 400.0%
        test-suite :: MultiSource/Benchmarks/ASCI_Purple/SMG2000/smg2000.test   1.00                              4.00 300.0%
               test-suite :: External/SPEC/CFP2006/447.dealII/447.dealII.test  65.00                            252.00 287.7%
            test-suite :: External/SPEC/CINT2006/464.h264ref/464.h264ref.test   3.00                              9.00 200.0%
                  test-suite :: MultiSource/Benchmarks/Olden/power/power.test   3.00                              7.00 133.3%
              test-suite :: MultiSource/Benchmarks/tramp3d-v4/tramp3d-v4.test  16.00                             33.00 106.2%
test-suite :: MultiSource/Benchmarks/MiBench/consumer-lame/consumer-lame.test   1.00                              2.00 100.0%
                test-suite :: MultiSource/Benchmarks/7zip/7zip-benchmark.test   4.00                              7.00  75.0%
        test-suite :: External/SPEC/CINT2006/483.xalancbmk/483.xalancbmk.test   7.00                              9.00  28.6%
                    test-suite :: External/SPEC/CINT2006/403.gcc/403.gcc.test  15.00                             17.00  13.3%
```
</details>

https://github.com/llvm/llvm-project/pull/70929