[NewPassManager] Add tuning option: LoopUnrolling [clang-change]

[asbirlea]

Summary

Use CodeGenOpts's setting for loop unrolling.
[to be coupled with D61618]

[chandlerc]

Same comment as on other Clang patch -- let's update an IR generation test to reflect this?

Should just be adding a RUN line.

[asbirlea]

Added test. Last RUN line fails before this patch (i.e. unrolling is not disabled with the given flag in the new pass manager).

[asbirlea]

Update test.

lib/CodeGen/BackendUtil.cpp

if (PGOOpt.hasValue()) {
                           CodeGenOpts.InstrProfileOutput.empty()
                               ? DefaultProfileGenName
                               : CodeGenOpts.InstrProfileOutput,
                           "", PGOOptions::NoAction, PGOOptions::CSIRInstr,
                           CodeGenOpts.DebugInfoForProfiling);
   }
 
   PipelineTuningOptions PTO;
+  PTO.LoopUnrolling = CodeGenOpts.UnrollLoops;
   // For historical reasons, loop interleaving is set to mirror setting for loop
   // unrolling.
   PTO.LoopInterleaving = CodeGenOpts.UnrollLoops;
   PTO.LoopVectorization = CodeGenOpts.VectorizeLoop;
   PTO.SLPVectorization = CodeGenOpts.VectorizeSLP;
 
   PassBuilder PB(TM.get(), PTO, PGOOpt);